NAMMA Praia Cape Verde Radiosonde
Table of Contents
Introduction
A radiosonde is just like a dropsonde, except it is not dropped from an airplane, it is launched upward into the atmosphere using a balloon. Measurements are taken on both the ascent and descent. The instrument measures the ambient pressure, temperature, relative humidity, as well as high resolution vertical measurements, accurate GPS altitudes, and detailed wind direction and speed.
Radiosondes were released from Praia, Cape Verde. The first radiosonde was released on August 18, 2006 at 1707 UTC. A radiosonde was released every four hours through September 9. Radiosonde releases resumed on September 10 at 1553 UTC but on a reduced release schedule of one per six hours. The last radiosonde was released on September 14 at 1132 UTC. In all there were 153 releases. The radiosonde flight log can be view here.
Campaign
These data files were generated during support of the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign, a field research investigation sponsored by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). This mission was based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa. Commencing in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets. For more information about the NAMMA Campaign, go to the NAMMA web site: http://namma.nsstc.nasa.gov/
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. Data are collected on both the ascent and descent.
The radiosondes released during the NAMMA campaign were Sippican MK IIa 403 MHz type with metalized chip thermistors and the ubiquitous Sippican resistive carbon relative humidity sensor. The balloons used were 350 gram with an expected burst pressure of 30-40 hPa. Originally, it was intended to release one chilled mirror radiosonde once each evening simultaneous with the MK IIa, to obtain more accurate relative humidity profiles. However, only 12 profiles were obtained. This document will supply a more detailed description of the radiosondes: https://ghrc.nsstc.nasa.gov/pub/doc/namma/namradio/namma_praia-radiosonde_description.pdf
File Naming Conventions
Data
The Praia radiosonde vertical profile data are in ASCII text files of two types, ascent and descent. The files are named:
namma_praia-radiosonde_YYYYMMDD_hhmmZ_data_<type>t_L2.txt
where,
YYYYMMDD = the UTC balloon release date as year-month-day, and
hhmm = the UTC balloon release time in hours-minutes, and
<type> = either ascent or descent
Browse
Browse images of the following types are also available in gif format:
NAMMA Praia-Radiosonde Skew-T Graph
NAMMA Praia-Radiosonde Balloon Trajectory Plot
NAMMA Praia-Radiosonde Total Precipitable Water Plot
NAMMA Praia-Radiosonde Wind Speed/Direction Plot
Example files:
namma_praia-radiosonde_20060818_1707z_skewt_lev2.gif
namma_praia-radiosonde_20060818_1707Z_traj_lev2.gif
namma_praia-radiosonde_20060818_1707Z_temp_dew_ql_lev2.gif
namma_praia-radiosonde_20060818_1707Z_wind_ql_lev2.gif
There are also a number of time series plots available:
NAMMA Praia-Radiosonde Temperature Time Series Plot
NAMMA Praia-Radiosonde Relative Humidity Time Series Plot
NAMMA Praia-Radiosonde u Component Wind Time Series Plot
NAMMA Praia-Radiosonde v Component Wind Time Series Plot
NAMMA Praia-Radiosonde Wind Vector Time Series Plot
Example files:
namma_praia-radiosonde_precipwater-timeseries.gif
namma_praia-radiosonde_relhumid-timeseries.gif
namma_praia-radiosonde_u-component-timeseries.gif
namma_praia-radiosonde_v-component-timeseries.gif
namma_praia-radiosonde_windspeed-timeseries.gif
namma_praia-radiosonde_windvector-timeseries.gif
Data Format
Below are two tables describing the radiosonde data. The user needs to be aware that there are two format sections: one for the up leg-tracked data and the second for the down leg track.
All radiosonde flights are tracked down to as low an altitude as allowed by the system. The data record at the point where the descent occurs has been split from the full file and designated "descent". The up track has been designated as "ascent".
Table 1 describes the header format of the file, which actually is the Metadata. Table 2 describes the data file contents and its format. The data file is in two parts. Part 1 is the up leg track data and part 2 is the down leg track. The up leg and down leg tracks are identified by the designator’s ‘ASCENT’ and ‘DESCENT’.
TABLE 1. DESCRIPTION OF THE PRAIA RADIOSONDE DATA FILE HEADER INFORMATION AND METADATA.
| Record Line No. |
Record content |
Record Description |
| 1 |
Balloon / radiosonde release date |
UTC date of detected sonde release based on host PC clock in month-day-year format (MM/DD/YY) |
| 2 |
Flight identification |
internal ground station track identification assigned to all files |
| 3 |
Radiosonde type |
edited manufacturer’s radiosonde model |
| 4 |
Radiosonde serial number |
manufacturer’s radiosonde serial number |
| 5 |
Station location sub-heading |
information sub-header only |
| 6 |
Station latitude |
latitude of balloon release site in decimal degrees |
| 7 |
Station longitude |
longitude of balloon release site in decimal degrees |
| 8 |
Station height |
the balloon release site height in meters above mean sea level |
| 9 |
Balloon release time |
the ground station identified balloon release time in UTC based on the host PC clock in hours-minutes-seconds format (hh:mm:ss) [Note: this is generally the time of the first frame aloft for the Sippican tracking software] |
| 10 |
Flight termination time |
the ground station identified flight termination time in UTC based on the host PC clock in hours-minutes-seconds format (hh:mm:ss) [Note: this time will generally NOT be the balloon burst time, but will represent the identified time of loss of track or when the operator manually ends the flight track] |
| 11 |
Surface data sub-heading |
information sub-header only |
| 12 |
Surface pressure observation |
surface pressure reading from AIR hand-held barometer; generally taken at 15 minutes prior to release |
| 13 |
Surface temperature observation |
surface temperature (dry bulb) reading from the sling psychrometer; generally taken at 15 minutes prior to release |
| 14 |
Surface relative humidity |
surface relative humidity determined from the sling psychrometer reading; generally taken at 15 minutes prior to release |
| 15 |
Surface wind direction |
surface wind direction reading; usually obtained at 15 minutes prior to release |
| 16 |
Surface wind speed |
surface wind speed reading; usually obtained at 15 minutes prior to release |
| 17 |
Flight segment |
indicator that this data file contains either the “ascent” or “descent” portion of the radiosonde track |
| 18 |
Filler record |
empty record spacer |
TABLE 2. DESCRIPTION OF THE PRAIA RADIOSONDE DATA FORMAT
Character
Positions |
Data Field |
Units |
Character Width |
Format |
Column Heading |
Missing Data |
| 001-001 |
filler |
|
1 |
1 space |
|
|
| 002-012 |
Flight Time Since Launch |
elapsed seconds |
11 |
seconds.xx |
ElpsTime[s] |
-999.00 |
| 013-013 |
filler |
|
1 |
1 space |
|
|
| 014-024 |
Pressure |
hPa |
11 |
fixed - 3 decimal places |
Press [hPa] |
-999.000 |
| 025-025 |
filler |
|
1 |
1 space |
|
|
| 026-036 |
Temperature |
degrees Celsius |
11 |
fixed - 2 decimal places |
Temp [C] |
-999.00 |
| 037-037 |
filler |
|
1 |
1 space |
|
|
| 038-048 |
Relative Humidity |
% |
11 |
fixed - 1 decimal places |
RH [%] |
-999.0 |
| 049-049 |
filler |
|
1 |
1 space |
|
|
| 050-060 |
Dew Point |
degrees Celsius |
11 |
fixed - 2 decimal places |
Dewpt [C] |
-999.00 |
| 061-061 |
filler |
|
1 |
1 space |
|
|
| 062-072 |
Geopotential Height |
meters |
11 |
fixed - 1 decimal places |
GeopHt [m] |
-999.0 |
| 073-073 |
filler |
|
1 |
1 space |
|
|
| 074-084 |
Smoothed Wind Direction |
degrees |
11 |
fixed - 1 decimal places |
Dir [deg] |
-999.0 |
| 085-085 |
filler |
|
1 |
1 space |
|
|
| 086-096 |
Smoothed Wind Speed |
meters per second |
11 |
fixed - 1 decimal places |
Speed [m/s] |
-999.0 |
| 097-097 |
filler |
|
1 |
1 space |
|
|
| 098-108 |
Smoothed Wind Comp. (E/W) |
meters per second |
11 |
fixed - 1 decimal places |
u [m/s] |
-999.0 |
| 109-109 |
filler |
|
1 |
1 space |
|
|
| 110-120 |
Smoothed Wind Comp. (N/S) |
meters per second |
11 |
fixed - 1 decimal places |
v [m/s] |
-999.0 |
| 121-121 |
filler |
|
1 |
1 space |
|
|
| 122-132 |
UTC Time |
hours:minutes:seconds |
11 |
hrs:mins:secs.x |
UTC [h:m:s] |
-999.0 |
| 133-133 |
filler |
|
1 |
1 space |
|
|
| 134-144 |
Latitude |
degrees |
11 |
fixed - 5 decimal places |
Lat [deg] |
-999.00000 |
| 145-145 |
filler |
|
1 |
1 space |
|
|
| 146-156 |
Longitude |
degrees |
11 |
fixed - 5 decimal places |
Lon [deg] |
-999.00000 |
An example of an ASCII data "ascent" file layout can be viewed here: Ascent Data File, and an ASCII "decent" file here: Decent Data File.
A chart of the available radiosonde products can be view here: Radiosonde Product Chart
Contact Information
The data provider is:
Francis (Frank) J. Schmidlin
GSFC, Wallops Island
Francis.J.Schmidlin@nasa.gov
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/
|
