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Data Set ID:

SMEX02 Soil Moisture Atmosphere Coupling Experiment (SMACEX), Iowa, Version 1

This data set contains measurements collected from flights conducted in June and July 2002 over the Walnut Creek watershed in central Iowa, USA.

Geographic Coverage

  • Atmospheric Temperature > Air Temperature
  • Atmospheric Pressure > Atmospheric Pressure Measurements
  • Atmospheric Chemistry > Carbon and Hydrocarbon Compounds > Carbon Dioxide
  • Atmospheric Winds > Flight Level Winds
  • Atmospheric Radiation > Heat Flux
  • Atmospheric Radiation > Net Radiation
  • Atmospheric Chemistry > Oxygen Compounds > Ozone
  • Atmospheric Temperature > Surface Air Temperature
  • Atmospheric Winds > Surface Winds
  • Vegetation > Vegetation Index
  • Atmospheric Winds > Vertical Wind Motion
  • Atmospheric Winds > Wind Profiles
Spatial Coverage:
  • N: 42, S: 41.85, E: -93.5, W: -93.9

Spatial Resolution: Not Specified
Temporal Coverage:
  • 15 June 2002 to 6 July 2002
Temporal Resolution: Not specified
Data Format(s):
  • Microsoft Excel
Platform(s) AIRCRAFT
Version: V1
Data Contributor(s): Ian MacPherson, Mengitsu Wolde
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

MacPherson, I. 2004. SMEX02 Soil Moisture Atmosphere Coupling Experiment (SMACEX), Iowa, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].

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Detailed Data Description


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

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File Size

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

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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.

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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.

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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
sec km m m degC degC degC W/m2 ppm degT
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
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Software and Tools

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Data Acquisition and Processing

Derivation Techniques and Algorithms

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.

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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.

Drawing of aircraft with sensor locations

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References and Related Publications

Contacts and Acknowledgments

Ian MacPherson
Mengistu Wolde

Flight Research Laboratory
National Research Council of Canada

Document Information


April 2004

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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