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.

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.

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/