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.
MacPherson, I. 2004. SMEX02 Soil Moisture Atmosphere Coupling Experiment (SMACEX), Iowa. Boulder, CO: National Snow and Ice Data Center. Digital media.
|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|
Flight Research Laboratory
National Research Council of Canada
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
Data are provided in both a Microsoft Excel file and an ASCII text file.
The Microsoft Excel file is 115 KB. The ASCII text file is 59 KB.
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
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.
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.
Data were recorded at 32 Hz and are provided as averages per flight.
The following table describes the column headings in the data table, and the parameters and sensors used.
|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|
|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|
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|
Data are available via FTP.
See Soil Moisture Experiment (SMEX) for more information.
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.
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.
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.
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|