SMEX02 Balloon-borne Radiosonde Data, Iowa

Summary

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. Radiosonde signals were received and processed by ground equipment, which automatically computed wind speed and direction using global navigation networks. The measurements were taken from 15 June 2002 to 9 July 2002. The site was located in the central watershed area during the Soil Moisture Experiment 2002 (SMEX02). Data are available from NSIDC via FTP.

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

Eichinger, W. 2004. SMEX02 Balloon-borne Radiosonde Data, Iowa. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format ASCII text files.
Spatial coverage and resolution 41.00°N, 93.61°W
Temporal coverage and resolution 15 June through 9 July 2002, one to four times daily
File naming convention File names consist of the prefix "rad" for radiosonde, followed by numbers representing the month, day, hour, minute, and year.
File size 1.59 KB to 7.9 KB
Parameter(s) Pressure, air temperature, relative humidity, dew point temperature, wind direction and speed.
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

William Eichinger
IIHR-Hydroscience and Engineering
University of Iowa

Technical Contact

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
e-mail: nsidc@nsidc.org

Acknowledgements

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

2. 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

Format

Data are provided in ASCII text files.

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.

File Size

File sizes range from 1.59 KB to 7.9 KB.

Spatial Coverage

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

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.

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
		

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume of data files is 324 KB.

Related Data Collections

See Soil Moisture Experiment (SMEX) for more information.

4. Data Acquisition and Processing

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.

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.

5. References and Related Publications

Iowa Institute of Hydraulic Research

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

AMSR-E Advanced Microwave Scanning Radiometer - Earth Observing System
FTP File Transfer Protocol
IIHR Iowa Institute of Hydraulic Research
SMEX Soil Moisture Experiment

Document Creation Date

April 2004

Document URL

http://nsidc.org/data/docs/daac/nsidc0231_smex_radiosonde.gd.html