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Data Set ID:

SMEX02 Balloon-borne Radiosonde Data, Iowa, Version 1

This data set includes radiosonde measurements of upper air temperature and pressure, relative humidity, and wind direction and speed during the balloons' ascent to the upper atmosphere.

Geographic Coverage

  • Atmospheric Temperature > Air Temperature
  • Atmospheric Pressure > Atmospheric Pressure Measurements
  • Atmospheric Water Vapor > Dew Point Temperature
  • Atmospheric Water Vapor > Humidity
  • Altitude > Station Height
  • Atmospheric Winds > Upper Level Winds
  • Ocean Winds > Vertical Wind Motion
  • Atmospheric Winds > Wind Profiles
Spatial Coverage:
  • N: 41, S: 41, E: -93.61, W: -93.61

Spatial Resolution: Not Specified
Temporal Coverage:
  • 15 June 2002 to 9 July 2002
Temporal Resolution: Not specified
Data Format(s):
  • ASCII Text
Platform(s) BALLOONS
Version: V1
Data Contributor(s): William Eichinger
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.

Eichinger, W. 2004. SMEX02 Balloon-borne Radiosonde Data, 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

The radiosonde data launches normally coincided with satellite overpasses, and in some cases multiple launches were made to characterize atmospheric boundary layer growth. The figure below shows the frequency of launches.

Launch frequency chart


Data are provided in ASCII text files.

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File Naming Convention

File names consist of the prefix "rad" for radiosonde, followed by numbers representing the month, day, hour, minute, and year. For example, the file "rad_062615022002.txt" was collected 26 June 2002 at 15:02 GMT.

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File Size

File sizes range from 1.59 KB to 7.9 KB.

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Total volume of data files is 324 KB.

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Spatial Coverage

Measurements were taken from the geographical coordinates 41.00°N, 93.61°W. Elevation is approximately 310 m above sea level.

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Temporal Coverage

Measurements were taken from 15 June through 9 July 2002. (Not all days were covered. Data are missing for 18, 19, and 20 June and 4, 5, and 7 July.)

Temporal Resolution

Launches took place between one and four times daily.

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Parameter or Variable

Parameter Description

Parameters are pressure, air temperature, relative humidity, dew point temperature, wind direction and speed.

The following table shows the data table elements and the units of measurement for the parameters. These data have been quality controlled; suspect or missing data has been flagged with a value of -999.

Header information (first line) Includes start time in time, day, month, and year.
Site information (second line) Includes station number, name of city, latitude, longitude, and elevation.
Data Columns Description Unit of Measurement
Time min Time after starting the measurements minutes
s Time after starting the measurements seconds
AscRate m/s Balloon ascent rate meters per second
Hgt/agl m Height above ground level meters
Pressure hPa Air pressure hectopascals
Temp degC Air Temperature degrees Celsius
RH % relative humidity percentage
Dewp degC Dew point temperature degrees Celsius
Dir deg Wind direction degree
Speed m/s Wind speed meters per second

Sample Data Record

The following sample was taken from the file "rad_062411532002.txt."

11:53	24	JUNE	2002	GMT					
02313	Kelley	42.00N	93.61W	310 m					
Time	AscRate	Hgt/agl	PressureTemp	RH	Dewp	Dir	Speed
min	s	m/s	m	hPa	degC	%	degC	deg	m/s

0	0	0.00	0	980.70	19.90	76	15.60	198	7.10
0	2	4.00	8	979.70	19.80	69	14.00	197	6.30
0	4	2.70	11	979.40	19.80	69	14.00	197	6.30
0	6	2.80	17	978.70	19.80	69	14.00	197	6.30
0	8	2.90	23	978.00	19.70	69	13.90	197	6.40
0	10	2.90	29	977.30	19.60	70	14.00	197	6.40
0	12	2.80	34	976.80	19.60	70	14.00	198	6.40
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Software and Tools

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Data Acquisition and Processing

Data Acquisition Methods

Measurements are based on use of the free-flying radiosonde, which transmitted data to the ground station over a 403 MHz radio link. Pressure, temperature and humidity were measured by sensors in the radiosonde. The location of the sonde was obtained by navigation networks (Navaids) via a receiver module on the sonde. The Navaid signals were relayed to the ground station for processing and computation of the wind profile.

The precision for atmospheric pressure is better than 1 hPa for pressures between 1060 hPa and 100 hPa, and better than 0.5 hPa for pressures between 100 hPa and 3 hPa.

The precision for air temperature is better than 0.2° C from -90° C to 60° C.

The precision for relative humidity of the air is 3%.

The precision for wind speed and direction is 0.5 m/s regardless of balloon distance from the ground system.

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Sensor or Instrument Description

The instrument used for the radiosonde was a DigiCORA MV11. This automatic rawinsonde set designed for accurate measurement of upper air pressure, temperature, relative humidity, and winds up to altitudes of 30 km. The measured data are processed automatically and given in standard meteorological formats.

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References and Related Publications

Contacts and Acknowledgments

William Eichinger
IIHR-Hydroscience and Engineering
University of Iowa


William P. Kustas and Fuquin Li of the USDA ARS Hydrology Lab.

Document Information


April 2004

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