CAMEX-3 Andros Island Rawinsonde and Radiosondes
Table of Contents
Introduction
The term radiosonde is a contraction for radio-sounding device. The instrument measures the ambient pressure, temperature, and moisture. When attached to a weather balloon filled with a lighter-than-air gas, radiosondes can attain heights in excess of 30 kilometers. Winds are determined from changes in the radiosonde position during the flight. The thermodynamic and wind data information are formulated into a "rawinsonde" observation.
Principles of operation
The radiosonde transmits its data to a ground-based telemetry system (antenna and receiver). This telemetry system receives the signals and forwards them to another module (signal processing system) to be decoded into meteorological units. Data are then passed to a computer for collection of data for the entire sounding and formulation of the observation products. When the balloon reaches it elastic limit and bursts, a parachute slows the descent of the radiosonde to the ground.
The radiosondes used at Andros Island were mostly GPS type radiosondes using full code-correlated transmission from up to 10 GPS satellites, providing accurate height and wind information allowing pressures to be calculated. A smaller number of radiosondes used Loran-C. Because of the location of Andros Island relative to the Loran-C transmitters little wind information was obtained from these sondes.
The GPS and MK-2 radiosondes typically use a carbon resistive relative humidity sensor (hygristor). A limited number of chilled mirror type radiosondes were be used to obtain more accurate relative humidity profiles. These chilled mirror instruments represent the mating of an old technolgy process with a new application - accurate chilled mirror measurements using an inexpensive radiosonde.
Data Naming Conventions and Data Format
Andros radiosonde data is archived into one composite tar file per day of the form:
cmx3andros_1998_ddd_daily.tar
Where ddd is the day of the year. When untarred, there will be files in ascii form representing the sonde data. Most data is in the UAIRP uniform 10-second and standard pressure level data output file format. However, some soundings have been subsetted to report only temperature/humidity data, and others to report only wind data. These sprinkled throughout the dataset, and are self explanatory.
The UAIRP format is as shown below. Note information (in blue below) concerning the type of sonde used for the sounding.
Location: Andros Island, Bahamas
Latitude: 24 deg. 42.00 min. North
Longitude: 077 deg. 46.12 min. West
Radiosonde Type: VIZ Mark II GPS LOS R/S Serial No.: 02263226
UAIRP Uniform 10-second and standard pressure level data output file format
Flight Date: 08/04/1998 Time: 19:26:33 UTC
Geop Rel Dew Mixng Spec Wind Wind Wind Wind Rise
Height Press Temp Hum Point Ratio Hum Dir Speed E-W N-S Rate
meters hPa deg C pct deg C g/kg g/kg deg m/s m/s m/s m/s
2.0 1013.80 29.2 27.0 23.1 6.788 6.714 95 6.0 -6.0 0.5 0.0
114.6 1001.67 28.7 26.8 7.7 6.615 6.546 87 4.9 -4.9 -0.3 4.2
129.4 1000.00 28.5 26.8 7.6 6.567 6.499 86 4.8 -4.8 -0.3 4.2
- Typically, the file name for these are of the form:
98ddd_tttt.ss_vz6.txt or 98ddd_tttt.ss_cm1.txt
Where tttt.ss is the start time in UTC hours, minutes and seconds. The nomenclature vz6 and cm1 indicates whether the sonde was of the VIZ hygristor type (old technology), or if it was one of the newer technology chilled mirror radiosonde.
- Additionally, we have included the University of Wisconsin sondes which were released from the nearby site in support of the Atmospheric Emitted Radiance Interferometer (AERI) experiment. These soundings are in either ASCII or NetCDF format, and have filenames of the form:
98ddd_tttt_uwsonde.txt or .cdf where tttt is the sonde launch time in UTC.
See the documentation for AERI dataset for more information about these data pertinant links.
Contact Information
To order these data or for further information, please contact:
Global Hydrology Resource Center
User Services
320 Sparkman Drive
Huntsville, AL 35805
Phone: 256-961-7932
E-mail: support-ghrc@earthdata.nasa.gov
Web: http://ghrc.nsstc.nasa.gov/
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