SMEX02 Soil Moisture Atmosphere Coupling Experiment (SMACEX), Iowa

Summary

This data set contains measurements collected from flights conducted in June and July 2002 over the Walnut Creek watershed in central Iowa, USA. The study was part of the Soil Moisture Experiment 2002 (SMEX02) and the Soil Moisture-Atmosphere Coupling Experiment (SMACEX), run by Canada's National Research Council (NRC). The aircraft carried numerous sensors and flew several flights per day along six tracks in the watershed area. Parameters for this data set include air pressure and temperature, dew point and radiometric temperature, greenness index, net radiation, CO₂ concentration, wind direction and speed, heat flux, and ozone flux.

These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.

Citing These Data

MacPherson, I. 2004. SMEX02 Soil Moisture Atmosphere Coupling Experiment (SMACEX), Iowa. Boulder, CO: National Snow and Ice Data Center. Digital media.

Overview Table

Category	Description
Data format	Microsoft Excel file or ASCII text file
Spatial coverage and resolution	41.85° to 42°N, -93.9° to -93.5°W Flights were made on 6 tracks per day, which averaged 5 km
Temporal coverage and resolution	Measurements were taken almost daily 15 June through 06 July 2002
File size	Microsoft Excel file is 115 KB ASCII text file is 59 KB
Parameter(s)	Air, dew point, and radiometric temperatures, greenness index, net radiation, CO2 concentration, wind direction, wind speed, sensible heat flux, latent heat flux, CO2 flux, friction velocity from momentum flux, and ozone flux
Procedures for obtaining data	Data are available via FTP

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Ian MacPherson
Mengistu Wolde
Flight Research Laboratory
National Research Council of Canada

Technical Contact

2. Detailed Data Description

Format

Data are provided in both a Microsoft Excel file and an ASCII text file.

File Size

The Microsoft Excel file is 115 KB. The ASCII text file is 59 KB.

Spatial Coverage

The study area was located in the Walnut Creek watershed in central Iowa, within in the following coordinates:

Southernmost Latitude: 41.85° N
Northernmost Latitude: 42° N
Westernmost Longitude: -93.9° W
Easternmost Longitude: -93.5° W

Spatial Resolution

Twin Otter flights were made on 6 tracks that varied in length from 3.04 to 6.5 km. Data were recorded at 32 Hz, at an airspeed of about 55 m/s. The resolution of the original time series was approximately 5 m.

Temporal Coverage

Measurements were taken between 15 June and 06 July 2002. Flights were made on the following days: 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 27, 29 June and 1, 3, 5, 6 July.

Temporal Resolution

Data were recorded at 32 Hz and are provided as averages per flight.

Parameter or Variable

The following table describes the column headings in the data table, and the parameters and sensors used.

Column	Type	Units	Description	Sensor
Run			Run number
GMT HR		hour	Greenwich Mean Time at start of run
GMT MIN		minute	Greenwich Mean Time at start of run
GMT SEC		seconds	Greenwich Mean Time at start of run
Duration		seconds	Duration of flight in seconds
DIST		km	Length of run
PALT	run-mean	m	Pressure altitude above mean sea level	Paroscientific 1003D-02 Rosemount 858AJ28 Probe
RALT	run-mean	m	Radio-altimeter height above terrain	Sperry AA-200 Radio Altimeter
TEMP	run-mean	°C	Air temperature	LI-COR C02 Analyzer Temp
DEWPT	run-mean	°C	Dew point temperature	E,G and G Model 137-S10
KT19	run-mean	°C	Radiometric surface temperature	Heitronics KT-19 Pyrometer
GRN	run-mean		Greenness Index (ratio of 730/660 nm reflected radiation)	Skye Industries Greenness sensor
NETRD	run-mean	W/m2	Net radiation from wingtip sensor	Kipp and Zonen CNR-1
CO2	run-mean	ppm	CO2 concentration	LI-COR C02/H20 Analyzer
HDG	run-mean	° true	Aircraft heading	Litton 90-100 IRS, Sperry C-12 Gyro Compass
WIND-dir	run-mean	° true	Wind direction	Rosemount probes
WIND-spd	run-mean	m/s	Wind speed	Rosemount probes
LWN-rms	rms	m/s	rms of wind component from north
LWE-rms	rms	m/s	rms of wind component from east
WEP-rms	rms	m/s	rms of vertical wind component
POT-rms	rms	°C	rms of potential temperature
RC02-rms	rms	mg/kg	rms of CO2 mixing ratio	LI-COR C02/H20 Analyzer
RH20-rms	rms	mg/kg	rms of H2O mixing ratio	LI-COR C02/H20 Analyzer
H	flux	W/m2	Sensible heat flux
LE	flux	W/m2	Latent heat flux
WC	flux	mg/m2/s	CO2 flux
U*	flux	m/s	Friction velocity computed from momentum flux
Ozone Flux	flux	µg/m2/s	Ozone flux, corrected	Scintrex Ozone Analyzer, TECO Ozone Analyzer

Sample Data Record

The following table shows just some of the data columns in the data file:

FLIGHT 01, 15-JUN-02
RUN	GMT HR	GMT MIN	GMT SEC	DURATION	DIST	PALT	RALT	TEMP	DEWPT	KT19	GRN	NETRD	C02	HDG
				sec	km	m	m	degC	degC	degC		W/m2	ppm	degT
TRACK	A
2	15	29	32	104	4.93	355	38	22.0	9.9	30.4	1.30	570	373	352
3	15	32	32	87	5.29	354	38	22.0	9.9	30.4	1.33	518	373	179
4	15	36	6	102	5.00	352	36	21.9	10.0	31.2	1.33	569	373	353
5	15	39	3	86	5.34	350	33	21.9	9.9	31.2	1.33	515	373	180
6	15	42	16	103	5.20	349	32	22.0	10.2	31.5	1.38	569	373	353
7	15	45	29	88	5.33	351	34	21.8	9.9	31.9	1.33	523	373	178

3. Data Access and Tools

Data Access

Data are available via FTP.

Related Data Collections

See Soil Moisture Experiment (SMEX) for more information.

4. Data Acquisition and Processing

Sensor or Instrument Description

Please see the parameter section for a list of the sensors used in the study. The figure below shows where the sensors were placed on the aircraft during SMACEX.

Processing Steps

Data were acquired by the various sensors on the aircraft and fed into a computer. Processing took place in September 2002 at NRC, employing updated calibrations as well as a Kalman filtering technique that removes small biases in the measured horizontal wind components. For complete information on processing, please refer to the SMACEX Special Report, available in the data directory.

5. References and Related Publications

Airborne Atmospheric Research, Remote Sensing and Aeromagnetics

Anderson, M.C. et al. 2003. Comparison of Aircraft- and Tower-Measured Fluxes Acquired During SMACEX with Predictions from a Regional Atmosphere-Land Exchange Model. Proceedings of the 17th Conference on Hydrology, American Meteorological Society. Long Beach, California, Feb. 9-12, 2003.

Kustas, W. P. et al. 2003. An Overview of the Soil Moisture Atmosphere-Coupling Experiment (SMACEX) in Central Iowa. Proceedings of the 17th Conference on Hydrology, American Meteorological Society. Long Beach, California, Feb. 9-12, 2003.

MacPherson, J. I., D.L. Marcotte, and J. E. Jordan. 2001. The NRC Atmospheric Research Aircraft. Canadian Aeronautics and Space Journal IAR 50th Anniversary Issue, Vol. 47, No. 3, pp. 147-157.

MacPherson, J. I. and M. Wolde. 2002. NRC Twin Otter Operations in the Soil Moisture-Atmosphere Coupling Experiment (SMACEX). National Research Council of Canada Report LTR-FR-190. 91 pp.

MacPherson, J. I., M. Wolde, W. P. Kustas, and J. H. Prueger. 2003. Aircraft and Tower-Measured Fluxes over Rapidly Growing Corn and Soy Bean Crops in Central Iowa. Proceedings of the 17th Conference on Hydrology, American Meteorological Society. Long Beach, California, Feb. 9-12, 2003.

Prueger, J. H. et al. 2003. Spatial Variability of Turbulent Fluxes Across a Corn/Soybean Production Region in Central Iowa. Proceedings of the 17th Conference on Hydrology, American Meteorological Society. Long Beach, California, Feb. 9-12, 2003.

SMACEX Special Report, available in the data directory.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

FTP	File Transfer Protocol
NRC	National Research Council
SMACEX	Soil Moisture Atmosphere Coupling Experiment
SMEX	Soil Moisture Experiment

Document Creation Date

April 2004

Document URL

http://nsidc.org/data/docs/daac/nsidc0232_smex_smacex.gd.html