Field Observations during the Eleventh Microwave Water and Energy Balance Experiment (MicroWEX-11): from April 25, 2012, through December 6, 20121

Tara Bongiovanni, Pang-Wei Liu, Karthik Nagarajan, Daniel Preston, Patrick Rush, Tim H.M. van Emmerik, Susan Steele-Dunne, Robert Terwilleger, Ella Baar, Max Wallace, Alejandro Monsivais-Huertero, Jasmeet Judge, Roger De Roo, Ruzbeh Akbar, and Anthony England 2

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1. Introduction

For accurate prediction of weather and near-term climate, root-zone soil moisture is one of the most crucial components driving the surface hydrological processes. Soil moisture in the top meter governs moisture and energy fluxes at the land–atmosphere interface, and it plays a significant role in partitioning of precipitation into runoff and infiltration.

Energy and moisture fluxes at the land surface during growing seasons of agricultural crops can be estimated by coupled Soil-Vegetation-Atmosphere-Transfer and crop growth models. Even though the biophysics of moisture and energy transport and of crop growth and development are well-captured in most current models, the errors in initialization, forcings, and computation accumulate over time and the model estimates of soil moisture in the root zone diverge from reality. Remotely sensed microwave observations can be assimilated in these models to improve root zone soil moisture and crop yield estimates.

The microwave signatures at low frequencies, particularly at 1–2 GHz (L-band) and 4–8 GHz (C-band) are very sensitive to soil moisture in the top few centimeters in most vegetated surfaces. Many studies have been conducted in agricultural areas—such as bare soil, grass, soybean, wheat, pasture, and corn—to understand the relationship between soil moisture and microwave remote sensing. It is important to know how microwave signatures vary with soil moisture, evapotranspiration (ET), and biomass during the growing season for a dynamic agricultural canopy with a significant wet biomass of 4–12 kg/m2.

2. Objectives

The goal of MicroWEX-11 was to conduct a season-long experiment, which incorporated active and passive microwave observations for bare soil, a growing season of elephant grass, and sweet corn. The variety of sensors allowed for further understanding of the land–atmosphere interactions during the growing season, and their effect on observed passive microwave signatures at 6.7 GHz and 1.4 GHz and active microwave signatures at 1.25 GHz. These observations match that of the satellite-based passive microwave radiometers, Advanced Microwave Scanning Radiometer-2 (AMSR-2), and the Soil Moisture and Ocean Salinity (SMOS) mission, respectively, and the recently launched National Aeronautics and Space Administration's Soil Moisture Active Passive (SMAP) mission. Specific objectives of MicroWEX-11 include the following:

  1. To acquire simultaneous active and passive data for bare soil, elephant grass, and corn.

  2. To collect passive and active microwave and other ancillary data to develop preliminary algorithms to estimate microwave signatures for bare soil, elephant grass, and corn.

  3. To evaluate feasibility of soil moisture retrievals using passive microwave data at 6.7 GHz and 1.4 GHz and active microwave data at 1.25 GHz for bare soil, growing elephant grass canopy, and corn.

  4. To gain insight in the diurnal variation of the dielectric constant of vegetation.

This report describes the observations conducted during the MicroWEX-11.

3. Field Setup

MicroWEX-11 was conducted at the UF/IFAS Extension Plant Science Research and Education Unit (PSREU), Citra, FL. Figures 1 and 2 show the location of the PSREU and the study site for the MicroWEX-11, respectively. The study site was located at the west side of the PSREU (29.4°N, 82.17°W). The instruments consisted of three ground-based microwave radiometer systems, a ground-based microwave radar system, and micrometeorological stations. The ground-based microwave radiometer systems were installed at the location shown in Figure 3(a–c), facing south to avoid the radiometer shadow interfering with the field of view. The ground-based microwave radar system was installed adjacent to the radiometer with a portion of the radar footprint overlapping the radiometer footprint, facing in the same direction as the radiometer system.

The dimensions of the bare soil study site were 65 m × 30 m with the corners of the field located at 29.4102°N 82.1763°W; 29.4102°N 82.1756°W; 29.4099°N 82.1756°W; 29.4100°N 82.1763°W. A linear move system was used for irrigation. The ground-based microwave radiometer and radar systems installation began on May 1 (Day of Year [DoY] 122) in 2012 with micrometeorological stations on DoY 123. (See Table B-1 for corresponding months and dates to the DoY mentioned in this document.) Three micrometeorological stations with soil moisture and soil temperature sensors were installed at the locations shown in Figure 3(a). On DoY 145, the soil moisture and soil temperature sensors were removed to conduct a seedless planting to simulate the roughness of a typical agricultural field during planting, and reburied on DoY 146. Rain gauges were installed on the south edge of the field in line with the outer edge of the UF L-band radiometer footprint and the UF L-band radar footprint. A thermal infrared sensor was installed south of the L-band station.

The dimensions of the elephant grass study site were 183 m × 183 m with the corners of the field located at 29.410°N 82.179°W; 29.410°N 82.177°W; 29.409°N 82.177°W; 29.409°N 82.179°W. The elephant grass (Pennisetum purpureum)—of varieties Merkeron, N-13, N-43, and N-51—was in its third year of growth. The row spacing was 182.9 cm (72 inches). A linear move system was used for irrigation. The ground-based microwave radiometer and radar systems installation began on DoY 165 with micrometeorological stations on DoY 170. Three micrometeorological stations with soil moisture and soil temperature sensors were installed at the locations shown in Figure 3(b). Rain gauges were installed south of the radar footprint in line with the outer edge of the UF L-band radiometer footprint and the UF L-band radar footprint. A relative humidity (RH) and temperature sensor were installed at the L-band station. A net radiometer and thermal infrared sensor were installed south of the C-band radiometer. On DoY 185, thermistors were installed to measure canopy temperature.

The dimensions of the corn study site were 100 m × 65 m with the corners of the field located at 29.4102°N 82.1765°W; 29.4102°N 82.1756°W; 29.4093°N 82.1765°W; 29.4093°N 82.1756°W. The corn of variety Yellow Supersweet Hybrid (SH2) Saturn was planted on DoY 230, at an orientation 0º from the east. The plant spacing was 18.4 cm (7 ¼ inches) and the row spacing was 91.4 cm (36 inches). A linear move system was used for irrigation. The ground-based microwave radiometer and radar systems installation began on DoY 227 with micrometeorological stations on DoY 233. Rain gauges were installed south of the radar footprint in line with the outer edge of the UF L-band radiometer footprint and the UF L-band radar footprint. Two micrometeorological stations with soil moisture and soil temperature sensors were installed at the locations shown in Figure 3(c). A thermal infrared sensor was installed south of the L-band station. Starting on DoY 282, dielectric measurements of the vegetation were taken. This report provides detailed information regarding sensors deployed and data collected during the MicroWEX-11.

Figure 1. Location of PSREU/IFAS.
Figure 1.  Location of PSREU/IFAS.
Credit: http://plantscienceunit.ifas.ufl.edu/directions.shtml

Figure 2. Location of the field site for MicroWEX-11 at the UF/IFAS PSREU.
Figure 2.  Location of the field site for MicroWEX-11 at the UF/IFAS PSREU.
Credit: http://plantscienceunit.ifas.ufl.edu/images/location/p1.jpg

Figure 3a. Layout of the sensors during MicroWEX-11 bare soil.
Figure 3a.  Layout of the sensors during MicroWEX-11 bare soil.

Figure 3b. Layout of the sensors during MicroWEX-11 elephant grass.
Figure 3b.  Layout of the sensors during MicroWEX-11 elephant grass.

Figure 3c. Layout of the sensors during MicroWEX-11 sweet corn.
Figure 3c.  Layout of the sensors during MicroWEX-11 sweet corn.

4. Sensors

MicroWEX-11 had six major types of instrument subsystems: (1) the ground-based University of Florida C-band and L-band radiometers, (2) the ground-based University of Michigan L-band radiometer, (3) the ground-based University of Florida L-band radar, (4) the dielectric measurements, (5) the micrometeorological, and (6) the soil subsystem.

4.1 University of Florida Microwave Radiometer Systems

4.1.1 University of Florida C-band Microwave Radiometer (UFCMR)

Microwave brightness temperatures at 6.7 GHz (λ = 4.48 cm) were measured every 15 minutes using the University of Florida's C-band Microwave Radiometer system (UFCMR) (Figure 4[a]). The radiometer system consisted of a dual polarization total power radiometer operating at the center frequency of 6.7 GHz housed atop a 10 m tower installed on a 16' trailer bed. The UFCMR was designed and built by the Microwave Geophysics Group at the University of Michigan. It operates at the center frequency at 6.7 GHz, which is near one of the center frequencies on the space-borne AMSR-2 aboard the Japan Aerospace Exploration Agency's Global Change Observation Mission-Water satellite. The UFCMR observed the 5.11 m × 4.67 m, 5.55 m × 4.84 m, and 5.18 m × 4.74 m footprint from a height of 7.15 m, 7.40 m, and 7.25 m for bare soil, elephant grass, and corn, respectively. A rotary system was used to rotate the look-angle of the UFCMR both for field observations and sky measurements. The brightness temperatures were observed at an incidence angle of 40°. The radiometer was calibrated at least once every week with a microwave absorber as warm load and measurement of sky as cold load. Figure 4(b) shows the close-up of the rotary system and 4(c) shows a close-up of the UFCMR antenna. Table 1 lists the UFCMR specifications. Figure A-1–A-3 shows the V- and H-pol brightness temperatures observed at C-band during MicroWEX-11 for the bare soil, elephant grass, and corn field.

Table 1. 

UFCMR specifications.

Parameter

Qualifier

Value

Frequency

Center

6.7 GHz

Bandwidth

3 dB

20 MHz

Beamwidth

3 dB V-pol elevationa

23°

3 dB V-pol azimuthb

21°

3 dB H-pol elevationc

21°

3 dB H-pol azimuthd

23°

Isolation

 

> 27 dB

Polarizations

Sequential

V/H

Receiver temp (Trec)

 

437 K

Noise Figure

From Trec

3.99 dB

RF gain

 

85 dB

NEDT

1 sec

0.71 K

8 sec

0.25 K

a sidelobes < -33 dB

b sidelobes < -28 dB

c sidelobes < -27 dB

d sidelobes < -35 dB

Figure 4. (a) The UFCMR system; (b) the side view of the UFCMR showing the rotary system; and (c) the front view of the UFCMR showing the receiver antenna.
Figure 4.  (a) The UFCMR system; (b) the side view of the UFCMR showing the rotary system; and (c) the front view of the UFCMR showing the receiver antenna.
Credit: J. Casanova, UF/IFAS

4.1.1.1 Theory of Operation

The UFCMR uses a thermoelectric cooler (TEC) for thermal control of the Radio Frequency (RF) stages for the UFCMR. This is accomplished by the Oven Industries "McShane" thermal controller. McShane is used to cool or heat by Proportional-Integral-Derivative (PID) algorithm with a high degree of precision at 0.01°C. The RF components are all attached to an aluminum plate that must have sufficient thermal mass to eliminate short-term thermal drifts. All components attached to this thermal plate,

The majority of the gain in the system is provided by a gain and filtering block designed by the University of Michigan for the STAR-Light instrument (De Roo 2003). The main advantage of this gain block is the close proximity of all the amplifiers, simplifying the task of thermal control. This gain block was designed for a radiometer working at the radio astronomy window of 1400–1427 MHz, and so the receiver is a heterodyne type with downconversion from the C-band RF to L-band. To minimize the receiver noise figure, a C-band low-noise amplifier (LNA) is used just prior to downconversion. To protect the amplifier from saturation due to out-of-band interference, a relatively wide bandwidth (but low insertion loss) bandpass filter is used just prior to the amplifier. Three components are between the filter and the antenna: a switch for choosing polarization, a switch for monitoring a reference load, and an isolator to minimize changes in the apparent system gain due to differences in the reflections looking upstream from the LNA.

The electrical penetrations use commercially available weatherproof bulkhead connections (Deutsch connectors or equivalent). The heat sinks have been carefully located employing RTV (silicone sealant) to seal the bolt holes. The radome uses 15 mil polycarbonate for radiometric signal penetration. It is sealed to the case using a rubber gasket held down by a square retainer.

The first SubMiniature version A (SMA) connection is an electromechanical latching, driven by the Z-World control board switches between V- and H-polarization sequentially. The SMA second latching that switches between the analog signal from the first switch and the reference load signal from a reference load resistor sends the analog signal to an isolator, where the signals within 6.4–7.2 GHz in radiofrequency are isolated. Then the central frequency is picked up by a 6.7 GHz bandpass filter, which also protects the amplifier from saturation. A low-noise amplifier (LNA) is used to eliminate the noise figure and adjust gain. A mixer takes the input from the LNA and a local oscillator to output a 1.4 GHz signal to STAR-Light. After the power amplifier and filtering block (Star-Light back-end), the signal is passed through a square law detector and a post-detection amplifier (PDA). The UFCMR is equipped with a microcontroller that is responsible for taking measurements, monitoring the thermal environment, and storing data until a download is requested. A laptop computer is used for running the user interface named FluxMon to communicate with the radiometer through Radiometer Control Language (RadiCL). The radiometer is configured to maintain a particular thermal set point, and make periodic measurements of the brightness at both polarizations sequentially and the reference load. The data collected by the radiometer are not calibrated within the instrument, since calibration errors could corrupt an otherwise useful dataset. Figure 5 shows the block diagram of the UFCMR.

Figure 5. Block diagram of the University of Florida C-band Microwave Radiometer.
Figure 5.  Block diagram of the University of Florida C-band Microwave Radiometer.
Credit: De Roo (2002)

4.1.2 University of Florida L-Band Microwave Radiometer (UFLMR)

Microwave brightness temperatures at 1.4 GHz (λ = 21.0 cm) were measured every 15 minutes using the University of Florida's L-band Microwave Radiometer system (UFLMR) (Figure 6[a]). The radiometer system consisted of a horizontally polarized total power radiometer operating at the center frequency of 1.4 GHz housed atop a 9.14 m tower installed on a 16' trailer bed. The UFLMR was designed and built by the Microwave Geophysics Group at the University of Michigan. It operates at the center frequency at 1.4 GHz, which is identical to the center frequency on the space-borne SMOS mission. The UFLMR observed the 5.51 m × 5.02 m, 5.28 m × 4.81 m, and 4.79 m × 4.36 m footprint from a height of 7.9 m, 7.76 m, and 6.87 m for bare soil, elephant grass, and corn, respectively. The brightness temperatures were observed at an incidence angle of 40°. A rotary system was used to rotate the look-angle of the UFLMR for both field observations and sky measurements. The radiometer was calibrated at least every week with a measurement of sky as cold load. Figure 6(b) shows a close up of the rotary system and Figure 6(c) shows the antenna of the UFLMR. Table 2 lists the UFLMR specifications. Figure A-1–A-3 shows the horizontally polarized brightness temperatures observed by the UFLMR during MicroWEX-11 for the bare soil, elephant grass, and corn field.

Figure 6. (a) The UFLMR system; (b) the side view of the UFLMR showing the rotary system; and (c) the front view of the UFLMR showing the receiver antenna.
Figure 6.  (a) The UFLMR system; (b) the side view of the UFLMR showing the rotary system; and (c) the front view of the UFLMR showing the receiver antenna.
Credit: J. Casanova, UF/IFAS

Table 2. 

UFLMR specifications.

Parameter

Qualifier

Value

Frequency

Center

1.4 GHz

Bandwidth

3 dB

20 MHz

Beamwidth

3 dB H-pol elevationa

22.5°

3 dB H-pol azimuthb

20.0°

Polarizations

Single

H

Receiver temp

(Trec)

 

179 K

Noise Figure

From Trec

2.1 dB

RF gain

 

79 dB

NEΔT

 

0.5 K

a sidelobes < -20 dB

b sidelobes < -30 dB

4.1.2.1 Theory of Operation

The UFLMR is similar to the UFCMR in many respects, using a thermoelectric cooler (TEC) for thermal control, a similar electromechanical switching mechanism, and a Z-World controller. The PDA is the same, and the software is a newer version of RadiCL. The RF block is designed for V- and H-pol switching. However, only the H-pol signal is guided from antenna to coax to the RF block, and the V-pol input to the RF block is a cold load (ColdFet).

In the RF block, the first switch alternates between V- and H-pol and the second alternates between the reference load and the signal from the first switch. An isolator prevents reflections of the input signal. After the isolator, the signal goes through a bandpass filter and then an LNA, followed by a series of bandpass filters and power amplifiers before the square law detector and the PDA. The microcontroller logs voltage and physical temperature measurements. Figure 7 shows the block diagram of the UFLMR.

Figure 7. Block diagram of the University of Florida L-band Microwave Radiometer.
Figure 7.  Block diagram of the University of Florida L-band Microwave Radiometer.
Credit: De Roo (2010)

4.2 University of Michigan Radiometer

4.2.1 Truck Mounted Radiometer System - L-band (TMRS-L)

The Truck Mounted Radiometer System (TMRS) is a dual-polarized, multi-frequency radiometer system from the University of Michigan that measures microwave brightness temperatures. The radiometer system consisted of a dual polarization total power radiometer housed atop a bucket truck. In this experiment, only the L-band radiometer, operating at the center frequency of 1.4 GHz (λ = 21.0 cm), was used to measure every-15-minute data (Figure 8[a]) in the corn field. The TMRS was designed and built by the Microwave Geophysics Group at the University of Michigan. The height, incident angle, and footprint were identical to the UFLMR. A rotary system was used to rotate the look angle of the TMRS both for field observations and sky measurements. The radiometer was calibrated at least every week with a measurement of sky as cold load. Figure 8(b) shows the antenna and Figure 8(c) shows the close-up of the rotary system of the TMRS-L. Table 3 lists the specifications of the TMRS-L. Figure A-1–A-3 shows the V- and H-pol brightness temperatures observed by the TMRS-L during MicroWEX-11 for the bare soil, elephant grass, and corn field.

Figure 8. (a) The TMRS-L; (b) the front view of the TMRS-L showing the receiver antenna; and (c) the side view of the TMRS-L showing the rotary system.
Figure 8.  (a) The TMRS-L; (b) the front view of the TMRS-L showing the receiver antenna; and (c) the side view of the TMRS-L showing the rotary system.
Credit: D. Preston, UF/IFAS

Table 3. 

TMRS-L specifications.

Parameter

Qualifier

Value

Frequency

Center

1.4 GHz

Bandwidth

3 dB

20 MHz

Beamwidth

3 dB H-pol elevation a

22.5°

3 dB H-pol azimuth b

20.0°

3 dB V-pol elevation c

20.0°

3 dB V-pol azimuth d

22.5°

Polarizations

Sequential

V/H

Receiver temp (Trec)

 

179 K

Noise Figure

From Trec

2.1 dB

RF gain

 

79 dB

NEΔT

 

0.5 K

a sidelobes < -20 dB

b sidelobes < -30 dB

c sidelobes < -30 dB

d sidelobes < -20 dB

4.2.1.1 Theory of Operation

The TMRS-L is similar to the UFLMR and UFCMR in many respects, using a thermoelectric cooler (TEC) for thermal control, a similar electromechanical switching mechanism and a Z-World controller; the PDA is the same, and the software is an older version of RadiCL. The RF block is designed for V- and H-pol switching similar to the UFCMR.

In the RF block, the first switch alternates between V- and H-pol and the second alternates between the reference load and the signal from the first switch. An isolator prevents reflections of the input signal. After the isolator, the signal goes through a bandpass filter and then an LNA, followed by a series of bandpass filters and power amplifiers before the square law detector and the PDA. The microcontroller logs voltage and physical temperature measurements.

4.3 University of Florida Radar System

4.3.1 University of Florida L-band Automated Radar System (UF-LARS)

Observations of radar backscatter (σ0) at four polarization combinations, (HH, VV, HV, and VH) and an azimuth range of 0° to 180° with an azimuthal resolution of 9° every 15 minutes resulting in 21 spatial samples were collected using the University of Florida L-band Automated Radar System (UF-LARS) (Figure 9). The UF-LARS is mounted on a 25 m Genie manlift and is comprised of three major sub-systems: (1) the antenna and the RF (ARF) sub-system, (2) the electro-mechanical positioning (EMP) sub-system, and (3) the software control and data acquisition (SDA) sub-system. Figure 10 shows a simplified block diagram of the UF-LARS. The RF subsystem was based upon the established designs for ground-based scatterometers employing a vector network analyzer with simultaneous acquisition of V- and H- polarized returns. These components operate at a center frequency of 1.25 GHz, with a bandwidth of 300 MHz and the one-way 3 dB beamwidth of 14.7° in the E-plane and 19.7° in the H-plane. The polarization isolation at the center frequency was > 37 dB for all principal planes and decreases to about 23 dB at the band edge of 1400 MHz. The EMP sub-system employs an embedded computer and is composed of three digital inclinometers, an elevation-over-azimuth controller, linear actuators, and a laser range finder. The elevation-over-azimuth controller was used to rotate the look-angle of the UF-LARS for both field observations and sky measurements. The antenna incidence angle was set to 40°, while the height was at 16.2 m giving a footprint of an arc, which has a footprint size of 1033.77 m2 based upon the 6 dB beamwidth. The SDA enabled system integration and automated data acquisition using a software control system designed in the Visual C++ environment. Radar calibration included sky measurements, a trihedral corner-reflector (Figure 9), and pole throughout the season. Table 4 summarizes the system specifications. More information regarding the UF-LARS can be found in Nagarajan et al. (2014). Figure A-4–A-6 shows the co-pol and cross-pol radar backscatter observed by the UF-LARS during MicroWEX-11 for the bare soil, elephant grass, and corn field, respectively.

Figure 9. UF-LARS mounted on the 25 m Genie platform. (Inset) Trihedral calibration target made of aluminum with an aperture length of 1.28 m.
Figure 9.  UF-LARS mounted on the 25 m Genie platform. (Inset) Trihedral calibration target made of aluminum with an aperture length of 1.28 m.
Credit: Nagarajan et al. (2014)

Figure 10. Sub-systems within the UF-LARS.
Figure 10.  Sub-systems within the UF-LARS.
Credit: Nagarajan et al. (2014)

Table 4. 

UF-LARS specifications.

Parameter

Value

Center frequency

1.25 GHz

Bandwidth

300 MHz

Number of channels

4

Antenna HPBW

14.7° (E-plane)

19.7° (H-plane)

4.4 Dielectric Properties

Using a microstrip line sensor, in-vivo dielectric property measurements were conducted on three maize leaves (leaf 8, 10, and 12) from October 8 (DoY 282) to October 19 (DoY 293). An electromagnetic wave is transmitted through a microstrip line resonator. The dielectric constant of the measured sample will modify the capacitance between the stripline and the ground plane, which changes the resonant frequency and the reflectivity of the stripline. Therefore, the change in resonant frequency of the sensor can be used to monitor changes in leaf dielectric properties. To obtain the most accurate results, the microstrip resonator was placed horizontally. Most leaves do not have a perfectly flat surface; so when a leaf is just placed on the sensor, the possibility exists that only an air bubble is measured. To prevent this, the leaf was placed between two Teflon blocks with a thickness of 1 cm. This created a layered measurement setup with a block of Teflon, the sensor, the leaf, and another block of Teflon. Also, Teflon has known constant dielectric properties, making the experiment more reproducible. The measurement setup is presented in Figure 11. All measurements were conducted using a ZVH8 Cable and Antenna Analyzer (ZVH8, 100 kHz to 8 GHz, Rohde & Schwarz, Munich, Germany) with the K42 Vector network Analysis (VNA) and K40 Remote Control option. The VNA sends out the electromagnetic wave to the microstrip line and measures the reflected signal (Van Emmerik 2013).

Figure 11. Setup used for the dielectric measurements.
Figure 11.  Setup used for the dielectric measurements.
Credit: Van Emmerik (2013)

Measurements were performed manually. Each measurement registered the magnitude [dB] and phase [°] of the reflection coefficient S11 at 1201 points between 2.1 and 4.1 GHz. From DoY 282–293, dielectric measurements were done at 6 a.m. and 6 p.m. corresponding to SMAP measurements. For all dielectric measurements, the following procedure was used. For every leaf, seven measurements were taken. First, a measurement of the Teflon block only was taken. This was done to be able to check the background noise and consistency of the measurements in time, since Teflon should yield the same results. Five measurements were taken on the leaf. Three were taken along the middle nerve of the leaf, at the collar, in the middle of the leaf, and at the tip of the leaf. In the middle of the leaf, two more measurements were taken, one on each side of the blade. Finally, a measurement was taken of air only. Figure 12 illustrates the measurement points on the leaves. Measurements were taken perpendicular at 90° and at 45° to the leaf. Figure A-7 shows the averaged resonant frequency at leaf 8, 10, and 12, including error bars that represent 1 standard deviation. The mean and standard deviation were determined with all 10 measurements (five locations, two angles).

Figure 12. Measurement points on leaf as used for the Citra field measurements, including the 90° and 45° measurement orientation of the microstrip line resonator.
Figure 12.  Measurement points on leaf as used for the Citra field measurements, including the 90° and 45° measurement orientation of the microstrip line resonator.
Credit: Van Emmerik (2013)

4.5 Net Radiometer

A Kipp and Zonen CNR-1 four-component net radiometer (Figure 13) was located in the elephant grass field, south of the C-band radiometer (as shown in Figure 3[b]), to measure up- and down-welling shortwave and longwave infrared radiation. The sensor consists of two pyranometers (CM-3) and two pyrgeometers (CG-3). The sensor was installed in the elephant grass field, south of the C-band radiometer, at the height of 2.95 m above ground and facing south on DoY 170. On DoY 226, the sensor was moved to a height of 4.8 m to stay above the plant canopy. Table 5 shows the list of specifications of the CNR-1 net radiometer. Figure A-8 shows the down- and up-welling solar (shortwave) and far infrared (longwave) radiation observed during MicroWEX-11.

Figure 13. CNR-1 net radiometer.
Figure 13.  CNR-1 net radiometer.
Credit: J. Casanova, UF/IFAS

Table 5. 

Specifications of the CNR-1 net radiometer.

Description

Value

Measurement spectrum: CM-3

305–2800 nm

Measurement spectrum: CG-3

5000–50000 nm

Response time

18 sec

Sensitivity

10–35 μV/(W/m2)

Pt-100 sensor temperature measurement

DIN class A

Accuracy of the Pt-100 measurement

± 2 K

Heating

Resistor 24 ohms, 6 VA at 12 volt

Maximum error due to heating: CM-3

10 W/m2

Operating temperature

-40º–70ºC

Daily total radiation accuracy

± 10%

Cable length

10 m

Weight

4 kg

Source: Campbell Scientific (2006a)

4.6 Air Temperature and Relative Humidity

Air temperature and relative humidity were measured every five minutes at the L-band station in the elephant grass field using a Campbell Scientific HMP45C Temperature and Relative Humidity Probe (Campbell Scientific 2006b). Figure A-9 shows the relative humidity and air temperature observations during MicroWEX-11.

4.7 Temperature in the Canopy

Starting on DoY 185, air temperature, from a height of 0 m to 4.0 m at increments of 0.5 m within the elephant grass canopy, was measured every five minutes west of the C-band station using thermistors on a tripod with an attached PVC pipe, as shown in Figure 14. Figure A-10 shows the canopy temperature observations during MicroWEX-11.

Figure 14. Canopy thermistors.
Figure 14.  Canopy thermistors.
Credit: D. Preston, UF/IFAS

4.8 Thermal Infrared Sensor

Two Apogee instruments IRR-PN thermal infrared sensors were installed during MicroWEX-11: one in the elephant grass and the other in the corn field site. Table 6 shows the list of specifications of the thermal infrared sensors.

Table 6. 

Specifications of the thermal infrared sensor (IRR-PN).

Description

Value

Field of view

 

18°half angle

Output

Target temp.

40 μV per ºC difference from sensor body

Sensor body temp.

0–2500 mV

Accuracy

-10ºC to 65ºC

±0.2ºC absolute accuracy

±0.1ºC uniformity

±0.05ºC repeatability

-40ºC to 70ºC

±0.5ºC absolute accuracy

±0.3ºC uniformity

±0.1ºC repeatability and uniformity

Optics

 

Germanium lens

Wavelength range

 

8–14 μm (corresponds to atmospheric window)

Response time

 

< 1 second to changes in target temperature

Input power

 

2.5 V excitation

Operating environment

 

-55–80ºC; 0–100% RH (non-condensing)

Water resistant, designed for continuous outdoor use

Cable

 

4.5 meters twisted, shielded 4 conductor wire with Santoprene casing.

Dimensions

 

6 cm long by 2.3 cm diameter

Mass

 

190 g

Source: Apogee Instruments Inc. (2007)

4.8.1 Thermal Infrared Sensor (Bare Soil)

The sensor was installed south of the L-band station (as shown in Figure 3[a]) at a height of 2.14 m to observe skin temperature at nadir. Figure A-11 shows the surface thermal infrared temperature observed during MicroWEX-11.

4.8.2 Thermal Infrared Sensor (Elephant Grass)

The sensor was installed south of the C-band radiometer (as shown in Figure 3[b]) at a height of 2.5 m to observe skin temperature at nadir. On DoY 223, the sensor was raised to 4.8 m. Figure A-12 shows the thermal infrared temperatures observed during MicroWEX-11.

4.8.3 Thermal Infrared Sensor (Sweet Corn)

The sensor was installed south of the L-band station (as shown in Figure 3[c]) at a height of 2.25 m to observe skin temperature at nadir. Figure A-13 shows the surface thermal infrared temperature observed during MicroWEX-11.

4.9 Soil Temperature Probes

Lab-made temperature probes, based on Campbell Scientific 107-l temperature sensor, were used to measure soil temperature.

4.9.1 Soil Temperature Probes (Bare Soil)

Forty-one temperature probes were placed at depths of 2, 4, 8, 16, 32, 64, and 150 cm measuring every five minutes. At the radar and L-band stations, the depths included two replicate at 2, 4, and 8 cm and one replicate at 16 and 32 cm. The C-band station included one replicate at 2, 4, 8, 16, and 32 cm and did not include a probe at 150 cm. Figure A-14– A-16 shows the soil temperatures observed at the L-band, C-band, and radar station, respectively, during MicroWEX- 11.

4.9.2 Soil Temperature Probes (Elephant Grass)

Forty-one temperature probes were placed at depths of 2, 4, 8, 16, 32, 64, and 150 cm measuring every five minutes. At the radar and L-band stations, the depths included two replicate at 2, 4, and 8 cm and one replicate at 16 and 32 cm. The C-band station included one replicate at 2, 4, 8, 16, and 32 cm and did not include a probe at 150 cm. Figure A-17– A-19 shows the soil temperatures observed at the L-band, C-band, and radar station, respectively during MicroWEX- 11.

4.9.3 Soil Temperature Probes (Sweet Corn)

Forty-one temperature probes were placed at depths of 2, 4, 8, 16, 32, 64, and 120 cm measuring every five minutes. At the radar and L-band stations, the depths included two replicate at 2, 4, and 8 cm and one replicate at 16 and 32 cm. The C-band station included one replicate at 2, 4, 8, 16, and 32 cm and did not include a probe at 120 cm. Figure A-20– A-22 shows the soil temperatures observed at the L-band, C-band, and radar station, respectively during MicroWEX- 11.

4.10 Soil Moisture Probes

Campbell Scientific time-domain water content reflectometers (CS616) were used to measure soil volumetric water content. The calibration coefficients were obtained from laboratory calibration and are listed in Table 7.

Table 7. 

The calibration coefficients for the CS616 probe.

Coefficient

Value

C0

1.5377

C1

0.1814

C2

-0.0070

C3

0.0001

4.10.1 Soil Moisture Probes (Bare Soil)

Forty-one reflectometers were placed at depths of 2, 4, 8, 16, 32, 64, and 150 cm measuring every five minutes. At the radar and L-band stations, the depths included two replicate at 2, 4, and 8 cm and one replicate at 16 and 32 cm. The C-band station included one replicate at 2, 4, 8, 16, and 32 cm and did not include a probe at 150 cm. Figure A-23–A-25 shows the volumetric soil moisture contents observed at the L-band, C-band, and radar station, respectively during MicroWEX-11.

4.10.2 Soil Moisture Probes (Elephant Grass)

Forty-one reflectometers were placed at depths of 2, 4, 8, 16, 32, 64, and 150 cm measuring every five minutes. For all three stations—radar, C-band, and L-band—the depths included two replicate at 2, 4, and 8 cm and one replicate at 16 and 32 cm. Figure A-26–A-28 shows the volumetric soil moisture contents observed at the L-band, C-band, and radar station, respectively during MicroWEX-11.

4.10.3 Soil Moisture Probes (Sweet Corn)

Forty-one reflectometers were placed at depths of 2, 4, 8, 16, 32, 64, and 120 cm measuring every five minutes. At the radar and L-band stations, the depths included two replicate at 2, 4, and 8 cm and one replicate at 16 and 32 cm. The C-band station included one replicate at 2, 4, 8, 16, and 32 cm and did not include a probe at 120 cm. Figure A-29–A-31 shows the volumetric soil moisture contents observed at the L-band, C-band, and radar station, respectively during MicroWEX-11.

4.11 Soil Moisture

Soil moisture measurements using a Dynamax TH2O Soil Moisture Meter were taken on DoY 226 in the elephant grass field. Due to heterogeneity of the elephant grass the UFLARS and the UFLMR were moved to the west side of the field. Multiple measurements were taken from the previous radar and radiometer footprints and the current footprints (Figure 3[b]). The averages and standard deviations of the measurements are shown in Table 8.

Table 8. 

Results from the Dynamax TH2O Soil Moisture Meter.

Location

Average VSM (m3/m3)

Std Dev VSM (m3/m3)

East

L-band

0.165

0.007

Radar

0.172

0.030

C-band

0.179

0.005

West

L-band

0.245

0.054

Radar

0.245

0.016

VSM = volumetric soil moisture

4.12 Precipitation

Precipitation and overhead irrigation was determined using six tipping-bucket rain gauges with locations shown in Figure 3(a–c).

4.12.1 Precipitation (Bare Soil)

Four tipping-bucket rain gauges, in line with the outer edge of the UFLMR footprint and at the outer edge of the UFLARS footprint were installed on DoY 128 at a height of 20 cm. Figure A-32 shows the observed precipitation.

4.12.2 Precipitation (Elephant Grass)

Two tipping-bucket rain gauges in line with the outer edge of the UFLMR footprint were installed on DoY 175 at a height of 20 cm above the ground to catch both precipitation and irrigation. Figure A-33 shows the observed precipitation and overhead irrigation.

4.12.3 Precipitation (Sweet Corn)

Four tipping-bucket rain gauges, two in line with the outer edge of the UFLMR footprint at a height of 3 m above the ground to stay above the height of the corn canopy and two in line with the outer edge of the UFLARS footprint at a height of 20 cm, were installed on DoY 243. Figure A-34 shows the observed precipitation.

5. Vegetation Sampling at the Elephant Grass Site

Vegetation properties in the sampling location, as shown in Figure 3(b), were measured weekly from DoY 201 until DoY 227 with a final sampling on DoY 335 during the field experiment. A vegetation sampling consisted of measurements of clump height and width, as well as biomass. Each sampling included one row of elephant grass in the sampling location. The sampling length started between two clumps and ended at the next midpoint between clumps that was greater than or equal to 4 m from the starting point.

5.1 Clump and Tiller Count

The clumps and tillers were counted for each sampling length in each of the four sampling areas. Three representative clumps were chosen to determine the percentages of small, medium, and large tillers in the sampling area. Figure A-35 and A-36 show the clumps and tillers per square meter.

5.2 Clump Height and Width

Maximum clump height and width were measured by placing a tape measure at the soil surface adjacent to the stems to the maximum height of the clump. The clump width, parallel to the row, was measured at the base of the clump. Figures A-37 and A-38 show the average of the maximum clump heights and widths during MicroWEX-11.

5.3 Wet and Dry Biomass

Using the sampling area, 10 tillers each of representative small, medium, and large were chosen from the three clumps in section 5.1. Each tiller was cut at the base, separated into leaves and stems, and weighed immediately. The samples were dried in the oven at 60ºC for one week for leaves and two weeks for stems. Figure A-39 shows the wet and dry biomass (in kg/m2) observed during MicroWEX-11 in the sampling area.

6. Vegetation Sampling at the Sweet Cornsite

Vegetation properties in two sampling locations as shown in Figure 3(c) were measured weekly during the field experiment. A vegetation sampling consisted of measurements of height, width, biomass, LAI, geometric description of the plant, and vertical distribution of moisture in the canopy. The crop density derived from the stand density (5.1 plants per m2) and row spacing (36?) was measured at the first sampling (DoY 250). Nine vegetation samplings were conducted on DoY 250, DoY 257, DoY 264, DoY 271, DoY 278, DoY 285, DoY 292, DoY 299, and DoY 306.

6.1 Height and Width

Crop height and width were measured by placing a measuring stick at the soil surface adjacent to the stem up to the maximum height of the crop. The maximum canopy width of the plant (parallel or perpendicular to the row) was also measured. Four representative plants were selected to obtain heights and widths inside each vegetation sampling area. Figure A-40 shows the average maximum crop heights and widths during MicroWEX-11.

6.2 Wet and Dry Biomass

Each sampling included one row of corn in the four sampling locations. The sampling length started between two plants and ended at the next midpoint between plants that was greater than or equal to one meter away from the starting point. The plants within this length were cut at the base, separated into leaves, stems, and ears, and weighed immediately. The samples were dried in the oven at 60ºC for one week and weighed. Figure A-41 shows the wet and dry biomass observed during MicroWEX-11 for the four sampling areas.

6.3 LAI

Destructive LAI was measured by taking two representative plants in the sampling area and separating the leaves. The leaves and the rest of the plant were dried in an oven at 60°C for one week to measure the dry weight of the leaf and the dry biomass of the sample. The ratio of the leaf dry weight to the dry biomass was used to calculate the fraction of leaf (FLEAF) in Equation 1 (Boote 1994). The length and width of each individual leaf of the four sample plants were also measured. Assuming a leaf as an ellipse, the area of the leaves was summed and divided by the dry mass of the leaves to calculate the specific leaf area (SLA). The total dry biomass (DM) was found using the procedure in 5.2. Equation 1 was used to determine the destructive LAI.

Equation 1. ?????? = ???? · ?????????? · ??????

The LAI obtained is shown in Figure A-42.

6.4 Vertical Distribution of Moisture in the Canopy

The wet and dry biomass of discrete vertical layers of individual corn plants was measured. Seven samplings were conducted during MicroWEX-11. Each sampling was conducted by selecting a representative plant at each sampling location. The plants were taken out of the ground with the roots still attached and taken indoors to prevent moisture loss. Each plant sample was carefully laid out on a metal sheet with grid spacing of 2 cm. The leaves were arranged to closely match their natural orientation in the field. The stem was cut every 10 cm as shown in Figure 15. The sample in each layer was weighed, both fresh and after drying in the oven at 60°C for 48 hours. Figure A-43 shows the wet and dry weights as a function of crop height during MicroWEX-11.

Figure 15. Subdividing plant samples into 10 cm layers.
Figure 15.  Subdividing plant samples into 10 cm layers.
Credit: D. Preston, UF/IFAS

6.5 Geometric Description

A geometric description of the plant consisted of the maximum length and width of each leaf of the sample plants, as shown in Figure 16. The stem circumference was measured by using a string to wrap around the base and around the tip of the plant to calculate the diameter of the stem. The ear length was measured while still in the husk from the base of the cob near the stem to the top, and the maximum circumference of the ear was measured by using a string. The stem length and diameter observed are shown in Figure A-44. Figure A-45 shows the height of each leaf. The leaf length and width are shown in Figures A-46 and A-47. The ear height, length, and diameter are shown in Figure A-48. The ear and leaf angles were measured from a digital photograph of a single plant taken while still in the field at each sampling area using a reference length such as a meter stick. The angle between the leaf and the stem (?1), the angle of the leaf fold (?2), and the ear angle (?e) were measured using an angle gage, as shown in Figure 17. See Figures A-49 and A-50 for the value of ?1 and ?2. Figure A-51 shows the ear angle for each ear.

Figure 16. Leaf length and width.
Figure 16.  Leaf length and width.
Credit: D. Preston, UF/IFAS

Figure 17. Leaf angles and ear angle location.
Figure 17.  Leaf angles and ear angle location.
Credit: R. Terwilleger, UF/IFAS

7. Well Sampling

7.1 Water Level Measurement

The water level measurement was processed by the Levelogger from Solinst Canada Ltd. The Leveloggers were installed at the northern wells in the elephant grass field and set to automatically record the water level every 30 minutes. The data were downloaded onto a laptop during the well sampling. Figure A-52 shows the water table elevation and depth during MicroWEX-11.

8. Soil Sampling

8.1 Soil Analysis

Soil sampling from three locations in the corn field was done on DoY 355. Samples included organic matter and texture analysis from depths of 0–10, 10, 20, 40, and 60 cm for the bare soil/corn site (Table 9), which were conducted by the UF/IFAS Extension Soil Testing Laboratory and the Soil and Water Science Soil Moisture Core Laboratory.

Table 9. 

The soil physical properties for the corn field site (percentages are given on a weight basis).

Bare Soil/Corn Soil Physical Properties

 

Sand (%)

Silt (%)

Clay (%)

OM (%)

Depth (cm)

Avg

SD

Avg

SD

Avg

SD

Avg

SD

0–10

94.975

0.940

2.165

1.648

2.860

0.707

1.975

0.007

10

95.475

1.648

2.165

1.648

2.360

0.000

2.035

0.191

20

95.475

1.648

2.165

1.648

2.360

0.000

1.975

0.021

40

96.140

0.707

1.500

0.707

2.360

0.000

0.985

0.035

60

95.140

2.121

2.000

1.414

2.860

0.707

0.920

0.057

8.2 Soil Surface Roughness

Soil roughness was measured in the bare soil field during the smooth period on DoY 132 and 138 and during the rough period on DoY 146 and 163 with a traditional grid board method (Table 10). Roughness measurements in the corn field were measured on DoY 243. The 2D surface profiles in directions parallel and perpendicular to the row structure during the bare soil period and parallel to the row structure during the corn field were measured using a 2 m long grid board. Jang et al. (2005) describes the grid board method in detail. Table 11 lists the root mean square height and correlation length measurements parallel and perpendicular to the row structure.

Figure 73. 
Figure 73. 

Table 11. 

Soil surface roughness measurements of root mean square height (s) and correlation length (cl).

 

Parallel to row structure

Perpendicular to row structure

DoY

s (cm)

cl (cm)

s (cm)

cl (cm)

132

0.41

5.64

0.68

9.8

138

0.42

12.35

0.7

9.33

146

0.45

1.78

1.71

9.45

163

0.36

12.87

1.3

12.22

243

0.41

7.59

9. Observations

For the microwave radiometric observations at C-band, the horizontally polarized brightness temperatures were found to be more sensitive to soil moisture than vertically polarized brightness temperatures during the short vegetation cover periods (Figure A-1–A-3). As the vegetation grew, it effectively masked the contribution of microwave emission from soil resulting in sensitivity decrease at both polarizations. Due to its higher penetration capability, the observations at lower frequencies (longer wavelengths), such as the L-band, were more sensitive to soil moisture during the growing season than at the higher frequencies of C-band (Figure A-1–A-3). The σ0VV was more sensitive to the vertical structure of growing vegetation in the mid- and late-stages of crop growth (Figure A-4–A-6). The resonant frequency at leaf 8 shows a clear diurnal difference, as the afternoon resonant frequencies are higher than the morning values. This indicated that the leaf is losing water during the day and recovers at night (Figure A-7).

The average down-welling shortwave radiation average was 190.57 W/m2 during the elephant grass growing season while the average up-welling shortwave radiation was 40.18 W/m2 (Figure A-8). The average relative humidity was 78.97%, while the average air temperature was 295.03 K (Figure A-9). At the end of the elephant grass season when the temperature becomes cooler, the temperature near the soil remains high while the canopy temperature decreases (Figure A-10). The average thermal infrared temperature was 298.30 K, 294.73 K, and 298.35 K for the bare soil, elephant grass, and corn field (Figure A-11–A-13). There were dryer conditions during the bare soil period than the elephant grass and corn season (Figure A-32–A-34). The water table decreased after DoY 300 (Figure A-52).

During the beginning of the season when vegetation was low, diurnal variations in soil temperature were maximum while later in the season the diurnal variations were minimal. Diurnal variations for soil temperatures at 64 cm and below were minimal throughout the season (Figure A-14–A-22). The change in soil moisture in the deeper layers was minimal during light rains (Figure A-23–A-31).

The average clump density for the elephant grass was 0.5 clump/m2 (Figure A-35). The tiller density was higher in the NW vegetation sampling area (Figure A-36). The maximum height of the canopy was 3.6 m (Figure A-37). The average clump was 0.50 m wide (Figure A-38). The biomass of the plant on the final sampling was 2.8 kg/m2 (Figure A-39).

The maximum height of the sweet corn was 1.7 m for the east vegetation sampling area, while the west was slightly shorter at 1.6 m (Figure A-40). The maximum width of the sweet corn plant was 1.01 m at the west vegetation sampling area (Figure A-40). The biomass of the plant continued to increase until reaching an equilibrium after DoY 271 (Figure A-41). The LAI increased before reaching a maximum of 2 m2/m2, and then decreasing slightly due to leaf senescence (Figure A-42). During ear formation the moisture per 10 cm section in the plant was higher at the ear location (Figure A-43). The length of the stem increased until DoY 292 when it leveled out (Figure A-44). The average stem diameter at the top of the stem was 0.012 m while the average diameter at the base of the stem was 0.020 m (Figure A-44). The maximum number of main leaves was 12 leaves (Figure A-45). The maximum leaf length was 0.8 m (Figure A-46) and the maximum leaf width was 0.10 m (Figure A-47). Each plant had 1–2 ears, with the highest ear not exceeding 0.70 m above the base (Figure A-48). The ear located highest on the plant was bigger in both length and diameter than the other ears on the plant (Figure A-48). For the leaf angles, ?1 ranged from 0°–90° from the vertical (Figure A-49) while ?2 ranged from 90°–180° (Figure A-50). The ear angle, ?e, was larger for the bigger ears (FigureA-51).

10. Bare Soil Feed Log

Table 12. 

April 30 (DoY 121)

 

Moved L-band to bare soil field

 

Moved C-band to bare soil field

 

Moved UM radiometer to bare soil field

May 1 (DoY 122)

 

Restarted L-band radiometer

 

Restarted C-band radiometer

 

Restarted UM radiometer

May 2 (DoY 123)

 

Buried L-band station sensor 2–8 cm, 2–32 cm, 2–150 cm

 

Buried C-band station sensor 2–32 cm, 2–64 cm

May 3 (DoY 124)

 

Buried Radar station sensor 2–32 cm, 2–150 cm

13:15

C-band radiometer calibration

14:03

L-band radiometer calibration

14:33

UM radiometer calibration

 

Started wiring in L-band and C-band station

May 5 (DoY 126)

10:46

Radar stopped

May 6 (DoY 127)

10:32

Restarted radar

May 7 (DoY 128)

 

Finish wiring in L-band and C-band station

 

Launched L-band, C-band, and radar station programs

 

Launched 4 rain gauges

May 8 (DoY 129)

 

Finish wiring in radar station

May 10 (DoY 131)

15:00

L-band radiometer calibration

16:00

C-band radiometer calibration

 

Buried and wired in radar station sensor 2–8 cm

May 11 (DoY 132)

9:00

UM radiometer calibration

 

Re-sent L-band, C-band, and radar station programs

 

Fixed L-band TDR 150 cm—blown fuse

 

Fixed L-band TDR 16 cm—blown fuse

 

Soil roughness measurements using grid board

11:20

Installed TIR at 2.14 m

May 14 (DoY 135)

12:27

UM radiometer calibration

 

Radar calibration

 

Dug up small L-band Pit 2 cm and 4 cm; sensors reburied

 

Rain

 

Dug up small L-band Pit 2 cm, 4 cm, and 8 cm sensors; reburied

 

Dug up 32 cm C-band Pit 2 cm and 4 cm; sensors reburied

May 17 (DoY 138)

 

C-band radiometer calibration

 

L-band radiometer calibration

 

UM radiometer calibration

 

Soil roughness measurements using grid board

May 21 (DoY 142)

13:16

UM radiometer calibration

May 24 (DoY 145)

9:43

UM radiometer calibration

9:46

C-band radiometer calibration

 

L-band radiometer calibration

15:00

Measurement from Susan

 

Dug up C-band, L-band, and radar soil sensors

May 25 (DoY 146)

 

Created rough surface

 

Reburied C-band, L-band, and radar soil sensors

May 31 (DoY 152)

9:32

C-band radiometer calibration

9:40

UM radiometer calibration

10:20

L-band radiometer calibration

June 4 (DoY 156)

 

Troubleshooting UM radiometer

June 5 (DoY 157)

 

Troubleshooting UM radiometer

June 7 (DoY 159)

9:40

C-band radiometer calibration

10:07

UM radiometer calibration

10:20

L-band radiometer calibration

 

Cleaned rain gauges of wasps and spiders

June 12 (DoY 164)

9:46

UM radiometer calibration

9:58

C-band radiometer calibration

10:47

L-band radiometer calibration

June 13 (DoY 165)

 

Radar calibration

 

Moved radar to elephant grass field

 

Moved L-band to elephant grass field

 

Moved C-band to elephant grass field

 

Moved UM radiometer to bare soil field

June 14–15 (DoY 167)

 

Disconnected and dug up station sensors in bare soil field

Note: Time is in Eastern Standard Time.

11. Elephant Grass Field Log

Table 13. 

March 26 (DoY 86)

 

L-band radiometer mounted (looking angle 40°; height 8 m)

April 3 (DoY 94)

 

Moved UM radiometer to elephant grass field

April 10 (DoY 101)

 

C-band radiometer mounted (looking angle 40°; height 8 m)

 

Adjusted time clock—UF L-band added 3 mins

 

Adjusted time clock—UF C-band added 33 mins

 

Adjusted time clock—UM L-band subtracted 1hr 53 mins

April 12 (DoY 103)

 

C-band radiometer calibration

 

L-band radiometer calibration

 

UM radiometer calibration

 

Adjusted gain and offset for UM radiometer

 

Calibrated UM inclinometer

April 19 (DoY 110)

9:20

C-band radiometer calibration

9:30

L-band radiometer calibration

 

UM radiometer calibration

 

Adjusted offset for UM radiometer

April 25 (DoY 116)

 

Critical area in elephant grass field cut by flail chopper

April 26 (DoY 117)

 

Critical area in elephant grass cleaned

April 27 (DoY 118)

 

Buried L-band station sensor 2–32 cm, 2–150 cm

 

Buried C-band station sensor 2–32 cm, 2–150 cm

April 30 (DoY 121)

 

Moved L-band to bare soil field

 

Moved C-band to bare soil field

 

Moved UM radiometer to bare soil field

June 13 (DoY 165)

 

Moved L-band to elephant grass field

 

Moved C-band to elephant grass field

 

Moved UM radiometer to elephant grass field

 

Moved radar to the elephant grass field

June 14 (DoY 166)

 

Restarted L-band radiometer

 

Restarted C-band radiometer

June 14 (DoY 167)5

 

Restarted UM radiometer

June 18 (DoY 170)

 

Started wiring in L-band station

 

Buried L-band station sensor 2–8 cm

 

Buried radar station sensor 2–8 cm, 2–32 cm, 2–150 cm

June 21 (DoY 173)

9:25

UM radiometer calibration

9:35

L-band radiometer calibration

10:20

C-band radiometer calibration

June 23 (DoY 175)

 

Launched two rain gauges

June 25 (DoY 177)

 

Power outage on 6/24/2012 due to tropical storm Debbie

8:30

Restarted C-band radiometer

8:45

Restarted L-band radiometer

 

Restarted radar running slow; restarted

June 27 (DoY 179)

 

Connected temperature/relative humidity probe

 

Re-sent L-band station program to include the newly installed probe

June 28 (DoY 180)

9:18

C-band radiometer calibration

10:35

L-band radiometer calibration

 

Radar calibration

 

Fixed UM radiometer

June 30 (DoY 182)

9:00

Power outage on 6/30/2012

14:00

Restarted C-band radiometer

14:00

Restarted UM radiometer

14:15

Restarted L-band radiometer

14:47

Restarted radar

July 3 (DoY 185)

10:45

UM radiometer calibration

 

Installed canopy thermistors (2.5 m and 3.5 m do not have solar shield)

July 5 (DoY 187)

9:55

L-band radiometer calibration

9:57

UM radiometer calibration

10:35

C-band radiometer calibration

July 12 (DoY 194)

14:05

L-band radiometer calibration

14:16

UM radiometer calibration

14:47

C-band radiometer calibration

 

Radar calibration

July 19 (DoY 201)

9:46

L-band radiometer calibration

9:47

UM radiometer calibration

 

Troubleshoot Z-world on UM radiometer

 

Elephant grass vegetation sampling

July 20 (DoY 202)

11:30

Restarted UM radiometer

July 23 (DoY 205)

10:35

UM radiometer calibration

July 24 (DoY 206)

10:32

Set the thermal setpoint to 305 K in UM radiometer

10:35

L-band radiometer calibration

11:05

C-band radiometer calibration

July 26 (DoY 208)

10:35

UM radiometer calibration

 

Elephant grass vegetation sampling

August 2 (DoY 215)

10:55

L-band radiometer calibration

10:55

UM radiometer calibration

11:32

C-band radiometer calibration

 

Radar calibration

 

Elephant grass vegetation sampling

August 8 (DoY 221)

9:01

L-band radiometer calibration

9:05

UM radiometer calibration

10:03

C-band radiometer calibration

 

Moved radar west due to patchiness in critical area

 

Moved L-band west due to patchiness in critical area

August 10 (DoY 223)

 

Elephant grass vegetation sampling

 

Installed solar shields on 2.5 m and 3.5 m canopy thermistors

 

Raised TIR to 4.8 m

August 13 (DoY 226)

10:03

Soil moisture sampling using a Dynamax TH2O Soil Moisture Meter

 

Raised CNR to 4.8 m

August 14 (DoY 227)

9:01

L-band radiometer calibration

9:25

C-band radiometer calibration

10:05

UM radiometer calibration

 

Radar calibration

 

Elephant grass vegetation sampling

 

Moved L-band to corn field

 

Moved C-band to corn field

 

Moved UM radiometer to corn field

 

Moved radar to corn field

August 15 (DoY 228)

 

Dug up C-band and radar station sensors

August 22 (DoY 235)

8:30

Flipped CNR to correct position

August 24 (DoY 237)

 

Removed two rain gauges from elephant grass field

August 31 (DoY 244)

 

Removed two rain gauges from elephant grass field

September 4 (DoY 248)

14:00

Lowered TIR and CNR for irrigation

September 11 (DoY 255)

14:00

Raised TIR and CNR

October 31 (DoY 305)

14:00

Lowered TIR and CNR for irrigation

November 1 (DoY 306)

9:00

Raised TIR and CNR

November 7 (DoY 312)

 

Lowered TIR and CNR for irrigation

November 8 (DoY 313)

 

Moved radar to elephant grass field

 

Moved UM radiometer to elephant grass field

 

Moved L & C-band radiometers to elephant grass field

11:30

Restarted UM radiometer to elephant grass field

November 11 (DoY 316)

 

Radar down–elevation motor

November 15 (DoY 320)

9:20

C-band radiometer calibration

10:00

L-band radiometer calibration

10:17

UM radiometer calibration

 

Replaced elevation motor in radar

 

Raised TIR and CNR

November 21 (DoY 326)

 

Flowering on edge of field; about to flower in critical area

9:20

C-band radiometer calibration

10:00

L-band radiometer calibration

10:17

UM radiometer calibration

November 29 (DoY 334)

11:45

L-band radiometer calibration

12:00

UM radiometer calibration

12:15

C-band radiometer calibration

November 30 (DoY 335)

 

Elephant grass vegetation sampling

December 4 (DoY 339)

22:00

Radar stopped

December 6 (DoY 341)

10:15

L-band radiometer calibration

10:15

UM radiometer calibration

 

Did not restart UM radiometer

11:00

C-band radiometer calibration

11:00

Restarted radar

December 12 (DoY 347)

15:15

Radar stopped

December 13 (DoY 348)

9:18

C-band radiometer calibration

10:47

L-band radiometer calibration

December 20 (DoY 355)

 

C-band radiometer calibration - absorber test

Note: Time is in Eastern Standard Time.

12. Sweet Corn Field Log

Table 14. 

August 14 (DoY 227)

 

Moved L-band to corn field

 

Moved C-band to corn field

 

Moved UM radiometer to corn field

 

Moved radar to corn field

August 15 (DoY 228)

9:15

Restarted L-band radiometer (height 6.10 m)

9:45

Restarted C-band radiometer

9:45

Restarted UM radiometer

August 17 (DoY 230)

 

Planted corn

August 20 (DoY 233)

 

Buried L-band station sensor 2–8 cm; 2–32 cm; 2–120 cm

 

Installed TIR at 2.25 m

 

Wired in L-band station

August 21 (DoY 234)

 

Sprayed field

 

Emergence

August 22 (DoY 235)

 

Buried radar station sensor 2–32 cm; 2–120 cm

 

Started wiring in radar station

August 23 (DoY 236)

 

Buried radar station sensor 2–8 cm

 

Buried C-band station sensor 2–32 cm; 2–64 cm

 

Finished wiring in radar station

August 24 (DoY 237)

9:03

L-band radiometer calibration

9:05

UM radiometer calibration

9:31

C-band radiometer calib

 

Reburied L-band station sensor 2 cm and 4 cm on 2–120 cm pit; tongs exposed

 

Moved TIR two rows south

August 28 (DoY 241)

 

Trouble shooting of radar station

 

Put new DeeBee in radar

 

Started wiring in C-band station

August 29 (DoY 242)

 

Trouble shooting of C-band station

 

Finished wiring in C-band station

August 30 (DoY 243)

9:01

C-band radiometer calibration

9:10

UM radiometer calibration

9:55

L-band radiometer calibration

 

Trouble shooting of C-band station

 

Installed two rain gauges in corn field

 

Soil roughness measurements using grid board

August 31 (DoY 244)

 

Installed two rain gauges in corn field

 

Temporary fix of coax cable in L-band radiometer

September 6 (DoY 250)

9:40

C-band radiometer calibration

10:35

L-band radiometer calibration

 

Changed coax cable in L-band radiometer

11:35

UM radiometer calibration

 

Changed coax cable in UM radiometer for H- and V-pols

 

Corn vegetation sampling

September 11 (DoY 255)

 

Fixed amplifier and switches in the RF box for radar

September 12 (DoY 256)

 

Radar calibration

September 13 (DoY 257)

9:10

C-band radiometer calibration

10:05

L-band radiometer calibration

10:40

UM radiometer calibration

 

Corn vegetation sampling

September 20 (DoY 264)

9:50

C-band radiometer calibration

10:03

UM radiometer calibration

10:35

L-band radiometer calibration

 

Radar calibration

 

Corn vegetation sampling

 

Tassel initiation

September 24 (DoY 268)

 

Dielectric measurements start

September 27 (DoY 271)

9:40

C-band radiometer calibration

9:47

UM radiometer calibration

 

L-band radiometer calibration

 

Corn vegetation sampling

 

Ear formation 50%

October 1 (DoY 275)

 

Silking 10%

October 4 (DoY 278)

9:31

C-band radiometer calibration

9:35

UM radiometer calibration

10:40

L-band radiometer calibration

 

Corn vegetation sampling

October 9 (DoY 283)

 

Radar stopped

October 11 (DoY 285)

10:00

C-band radiometer calibration

10:05

UM radiometer calibration

 

Power failure

14:30

Restarted C-band radiometer

14:45

Restarted UM radiometer

14:47

L-band radiometer calibration

15:30

Restarted L-band radiometer

 

Calibrated radar

 

Restarted radar

 

Corn vegetation sampling

October 13 (DoY 287)

 

Radar down–crane failure

October 18 (DoY 292)

9:20

C-band radiometer calibration

9:20

UM radiometer calibration

10:17

L-band radiometer calibration

 

Corn vegetation sampling

October 19 (DoY 293)

 

Dielectric measurements end

October 23 (DoY 297)

9:20

Removed ears in the critical area

October 25 (DoY 299)

9:20

UM radiometer calibration

9:25

L-band radiometer calibration

10:32

C-band radiometer calibration

October 26 (DoY 300)

 

Corn vegetation sampling

October 30 (DoY 304)

 

Removed leaves in the critical area

October 31 (DoY 304)

13:00

Radar stopped

November 1 (DoY 306)

9:25

C-band radiometer calibration

9:46

Restarted radar

10:02

L-band radiometer calibration

10:05

UM radiometer calibration

 

Corn vegetation sampling

November 8 (DoY 313)

9:10

C-band radiometer calibration

9:50

L-band radiometer calibration

9:55

UM radiometer calibration

 

Radar calibration

 

Moved radar to elephant grass field

 

Moved UM radiometer to elephant grass field

 

Moved L & C-band radiometers to the elephant grass field

December 20 (DoY 355)

 

Soil samples collected

13. References

Apogee Instruments, Inc. 2007. Infrared Radiometer Owner's Manual, Model: IRR-PN. Logan, UT: Apogee Instruments.

Boote, K. J. 1994. "Data Requirements for Model Evaluation and Techniques for Sampling Crop Growth and Development." In DSSAT Version 3.5, Volume 4, edited by Gerrit Hoogenboom, Paul W. Wilken, and Gordon Y. Tsuji. 215–220. Honolulu: University of Hawaii.

Campbell Scientific. 2006a. CNR1 Net Radiometer Instruction Manual. Logan, UT: Campbell Scientific.

Campbell Scientific. 2006b. Campbell Scientific Model HMP45C Temperature and Relative Humidity Probe Instruction Manual. Logan, UT: Campbell Scientific.

De Roo, R. D. 2002. University of Florida C-band Radiometer Summary. Ann Arbor: Space Physics Research Laboratory, University of Michigan.

De Roo, R. D. 2003. TMRS-3 Radiometer Tuning Procedures. Ann Arbor: Space Physics Research Laboratory, University of Michigan. De Roo, R. D. 2010. Personal communication.

Jang, M. Y., K. C. Tien, J. J. Casanova, and J. Judge. 2005. Measurements of soil surface roughness during the fourth microwave water and energy balance experiment: April 18 through June 13, 2005. Circular 1483. Gainesville: University of Florida Institute of Food and Agricultural Sciences. .

Nagarajan, K., P. W. Liu, R. DeRoo, J. Judge, R. Akbar, P. Rush, S. Feagle, D. Preston, and R. Terwilleger. "Automated L-Band Radar System for Sensing Soil Moisture at High Temporal Resolution." IEEE Geosci. and Remote Sens. Letters 11(2).

Van Emmerik, Tim H. M. 2013. "Diurnal differences in vegetation dielectric constant as a measure of water stress." PhD diss., Delft University of Technology.

14. Acknowledgments

The authors would like to acknowledge Mr. James Boyer and his team at the PSREU, Citra, Florida, for excellent field management. MicroWEX-11 was supported by grants from NASA-THP (Grant number: NNX09AK29G) and Netherlands Organization for Scientific Research (NWO) Veni Grant Program (ALW 863.09.015).

A. Field Observation

Figure A-1. Microwave brightness at C-band and L-band at vertical and horizontal polarization (bare soil).
Figure A-1.  Microwave brightness at C-band and L-band at vertical and horizontal polarization (bare soil).

Figure A-2. Microwave brightness at C-band and L-band at vertical and horizontal polarization (elephant grass).
Figure A-2.  Microwave brightness at C-band and L-band at vertical and horizontal polarization (elephant grass).

Figure A-3. Microwave brightness at C-band and L-band at vertical and horizontal polarization (sweet corn).
Figure A-3.  Microwave brightness at C-band and L-band at vertical and horizontal polarization (sweet corn).

Figure A-4. Radar backscatter at co-pol and cross-pol (bare soil).
Figure A-4.  Radar backscatter at co-pol and cross-pol (bare soil).

Figure A-5. Radar backscatter at co-pol and cross-pol (elephant grass).
Figure A-5.  Radar backscatter at co-pol and cross-pol (elephant grass).

Figure A-6. Radar backscatter at co-pol and cross-pol (sweet corn).
Figure A-6.  Radar backscatter at co-pol and cross-pol (sweet corn).

Figure A-7. Bulk leaf water content and resonant frequencies of the microstrip line sensor.
Figure A-7.  Bulk leaf water content and resonant frequencies of the microstrip line sensor.

Figure A-8. Down- and up-welling shortwave and longwave radiation.
Figure A-8.  Down- and up-welling shortwave and longwave radiation.

Figure A-9. Relative humidity and air temperature.
Figure A-9.  Relative humidity and air temperature.

Figure A-10. Canopy temperature.
Figure A-10.  Canopy temperature.

Figure A-11. Surface temperature (TIR) (bare soil).
Figure A-11.  Surface temperature (TIR) (bare soil).

Figure A-12. Surface temperature (TIR) (elephant grass).
Figure A-12.  Surface temperature (TIR) (elephant grass).

Figure A-13. Surface temperature (TIR) (sweet corn).
Figure A-13.  Surface temperature (TIR) (sweet corn).

Figure A-14. L-band station soil temperature (bare soil).
Figure A-14.  L-band station soil temperature (bare soil).

Figure A-15. C-band station soil temperature (bare soil).
Figure A-15.  C-band station soil temperature (bare soil).

Figure A-16. Radar station soil temperature (bare soil).
Figure A-16.  Radar station soil temperature (bare soil).

Figure A-17. L-band station soil temperature (elephant grass).
Figure A-17.  L-band station soil temperature (elephant grass).

Figure A-18. C-band station soil temperature (elephant grass).
Figure A-18.  C-band station soil temperature (elephant grass).

Figure A-19. Radar station soil temperature (elephant grass).
Figure A-19.  Radar station soil temperature (elephant grass).

Figure A-20. L-band station soil temperature (sweet corn).
Figure A-20.  L-band station soil temperature (sweet corn).

Figure A-21. C-band station soil temperature (sweet corn).
Figure A-21.  C-band station soil temperature (sweet corn).

Figure A-22. Radar station soil temperature (sweet corn).
Figure A-22.  Radar station soil temperature (sweet corn).

Figure A-23. L-band station soil moisture (bare soil).
Figure A-23.  L-band station soil moisture (bare soil).

Figure A-24. C-band station soil moisture (bare soil).
Figure A-24.  C-band station soil moisture (bare soil).

Figure A-25. Radar station soil moisture (bare soil).
Figure A-25.  Radar station soil moisture (bare soil).

Figure A-26. L-band station soil moisture (elephant grass).
Figure A-26.  L-band station soil moisture (elephant grass).

Figure A-27. C-band station soil moisture (elephant grass).
Figure A-27.  C-band station soil moisture (elephant grass).

Figure A-28. Radar station soil moisture (elephant grass).
Figure A-28.  Radar station soil moisture (elephant grass).

Figure A-29. L-band station soil moisture (sweet corn).
Figure A-29.  L-band station soil moisture (sweet corn).

Figure A-30. C-band station soil moisture (sweet corn).
Figure A-30.  C-band station soil moisture (sweet corn).

Figure A-31. Radar station soil moisture (sweet corn).
Figure A-31.  Radar station soil moisture (sweet corn).

Figure A-32. Rainfall and overhead irrigation (bare soil).
Figure A-32.  Rainfall and overhead irrigation (bare soil).

Figure A-33. Rainfall and overhead irrigation (elephant grass).
Figure A-33.  Rainfall and overhead irrigation (elephant grass).

Figure A-34. Rainfall and overhead irrigation (sweet corn).
Figure A-34.  Rainfall and overhead irrigation (sweet corn).

Figure A-35. Clumps in one square meter.
Figure A-35.  Clumps in one square meter.

Figure A-36. Tillers in one square meter.
Figure A-36.  Tillers in one square meter.

Figure A-37. Averages and standard deviations of the maximum clump height.
Figure A-37.  Averages and standard deviations of the maximum clump height.

Figure A-38. Averages and standard deviations of the base width.
Figure A-38.  Averages and standard deviations of the base width.

Figure A-39. Wet and dry canopy biomass.
Figure A-39.  Wet and dry canopy biomass.

Figure A-40. Average crop height and width (sweet corn).
Figure A-40.  Average crop height and width (sweet corn).

Figure A-41. Wet and dry canopy biomass (sweet corn).
Figure A-41.  Wet and dry canopy biomass (sweet corn).

Missing Figure (FIGURE 61)

Figure A-43. Vertical distribution of wet and dry biomass.
Figure A-43.  Vertical distribution of wet and dry biomass.

Figure A-44. Stem length and diameter.
Figure A-44.  Stem length and diameter.

Figure A-45. Leaf height.
Figure A-45.  Leaf height.

Figure A-46. Leaf length.
Figure A-46.  Leaf length.

Figure A-47. Leaf width.
Figure A-47.  Leaf width.

Figure A-48. Ear height, length, and diameter.
Figure A-48.  Ear height, length, and diameter.

Figure A-49. Leaf angle (?1).
Figure A-49.  Leaf angle (?1).

Figure A-50. Leaf angle (?2).
Figure A-50.  Leaf angle (?2).

Figure A-51. Ear angle (?e).
Figure A-51.  Ear angle (?e).

Figure A-52. Water table depth and elevation above sea level.
Figure A-52.  Water table depth and elevation above sea level.

B. Julian Day Calendar

Table B-1. 

Julian Day Calendar for leap years.

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

1

1

32

61

92

122

153

183

214

245

275

306

336

2

2

33

62

93

123

154

184

215

246

276

307

337

3

3

34

63

94

124

155

185

216

247

277

308

338

4

4

35

64

95

125

156

186

217

248

278

309

339

5

5

36

65

96

126

157

187

218

249

279

310

340

6

6

37

66

97

127

158

188

219

250

280

311

341

7

7

38

67

98

128

159

189

220

251

281

312

342

8

8

39

68

99

129

160

190

221

252

282

313

343

9

9

40

69

100

130

161

191

222

253

283

314

344

10

10

41

70

101

131

162

192

223

254

284

315

345

11

11

42

71

102

132

163

193

224

255

285

316

346

12

12

43

72

103

133

164

194

225

256

286

317

347

13

13

44

73

104

134

165

195

226

257

287

318

348

14

14

45

74

105

135

166

196

227

258

288

319

349

15

15

46

75

106

136

167

197

228

259

289

320

350

16

16

47

76

107

137

168

198

229

260

290

321

351

17

17

48

77

108

138

169

199

230

261

291

322

352

18

18

49

78

109

139

170

200

231

262

292

323

353

19

19

50

79

110

140

171

201

232

263

293

324

354

20

20

51

80

111

141

172

202

233

264

294

325

355

21

21

52

81

112

142

173

203

234

265

295

326

356

22

22

53

82

113

143

174

204

235

266

296

327

357

23

23

54

83

114

144

175

205

236

267

297

328

358

24

24

55

84

115

145

176

206

237

268

298

329

359

25

25

56

85

116

146

177

207

238

269

299

330

360

26

26

57

86

117

147

178

208

239

270

300

331

361

27

27

58

87

118

148

179

209

240

271

301

332

362

28

28

59

88

119

149

180

210

241

272

302

333

363

29

29

60

89

120

150

181

211

242

273

303

334

364

30

30

 

90

121

151

182

212

243

274

304

335

365

31

31

 

91

 

152

 

213

244

 

305

 

366

Footnotes

1. This document is AE514, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date April 2015. Revised January 2019. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication.
2. Tara Bongiovanni, former graduate research assistant; Pang-Wei Liu, former graduate research assistant; Karthik Nagarajan, post-doctoral researcher, CRS, ABE; Daniel Preston, researcher, QualComm; Patrick Rush, engineer, CRS, ABE; Tim H.M. van Emmerik, Civil Engineering Department, Delft University of Technology; Susan Steele-Dunne, Civil Engineering Department, Delft University of Technology; Robert Terwilleger, undergraduate research assistant, CRS, ABE; Ella Baar, undergraduate research assistant, CRS, ABE; Max Wallace, undergraduate research assistant, CRS, ABE; Alejandro Monsivais-Huertero, associate professor, ESIME Unidad Ticomán,Instituto Politécnico Nacional, Mexico; Jasmeet Judge, assistant professor and director, CRS, Department of Agricultural and Biological Engineering; Roger De Roo, Electrical Engineering and Computer Sciences Department, University of Michigan; Ruzbeh Akbar, Electrical Engineering and Computer Sciences Department, University of Michigan; and Anthony England, Electrical Engineering and Computer Sciences Department; UF/IFAS Extension, Gainesville, FL 32611.

Publication #AE514

Date: 2019-05-23

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