GRIP DC-8 Dropsonde

Table of Contents

Introduction

The NCAR GPS Dropsonde system, also known as AVAPS (Airborne Vertical Atmospheric Profiling System), has dramatically extended the envelope of atmospheric profiling capabilities. Since its debut in 1997, it has flown on numerous missions in support of operational weather forecasting and atmospheric research, with impressive results.

The dropsonde instrument is ejected from a tube in the underside of the DC8 aircraft. As the dropsonde floats to the surface on a parachute, it continuously measures and transmits via a 400 MHz meteorological band telemetry link, pressure, temperature and relative humidity, as well as GPS-based wind formation data, to the receiving system onboard the aircraft. Dropsondes are fitted with Global Positioning System receivers to measure the atmospheric state parameters (temperature, humidity, windspeed/direction, pressure) and location in 3 dimensional space during the sonde's descent once each half second. Measurements are transmitted to the aircraft from the time of release until impact with the ocean's surface.

The GRIP NASA DC-8 Dropsonde dataset has undergone NCAR/EOL quality control, see readme_GRIP-2010_DC8_dropsondes.pdf for details. Data was collected for the GRIP campaign from 17 Aug 2010 to 22 Sep 2010. Sixteen NASA DC-8 aircraft research flights were completed and three hundred twenty eight dropsondes were deployed over the Atlantic Ocean during that time.

The Genesis and Rapid Intensification Processes (GRIP) experiment was a NASA Earth science field experiment conducted August 5 to September 30, 2010. The major goal was to better understand how tropical storms form and develop into major hurricanes. NASA used the DC-8 aircraft, the WB-57 aircraft and the Global Hawk Unmanned Airborne System (UAS), configured with a suite of in situ and remote sensing instruments that were used to observe and characterize the lifecycle of hurricanes. This campaign also capitalized on a number of ground networks and space-based assets, in addition to the instruments deployed on aircraft from Ft. Lauderdale, Florida ( DC-8), Houston, Texas (WB-57), and NASA Dryden Flight Research Center, California (Global Hawk). More information about this Campaign can be found on the GRIP web site: https://ghrc.nsstc.nasa.gov/home/field-campaigns/grip

NASA's DC-8 dropsonde system uses an integrated, highly accurate, GPS-located atmospheric profiling dropsonde, which measures and records current atmospheric conditions in a vertical column below the aircraft. The dropsonde, also known as dropwindsonde or parachute radiosonde, is a small, lightweight (less than 1 lb) cylindrical instrument that falls freely through the atmosphere, slowed somewhat by a small inflatable parachute. This type of instrument offers atmospheric researchers a complete solution for accurate in-situ measurement of the atmosphere.

A unique square-cone parachute is used to reduce the initial shock load and to slow and stabilize the descending dropsonde. The parachute is deployed immediately on exit from the launch chute and takes about five seconds to be filled by ram-air. The square-cone parachute is very stable during the descent, reducing or eliminating any pendulum motion of the dropsonde.

Once deployed, the launch crew does not expect to see the instrument again. The cost of recovering a dropsonde would likely exceed its value. Also, since they are mostly launched over water, the probability of finding them would be low.

Additional information about dropsondes can be found here: http://www.eol.ucar.edu/rtf/facilities/dropsonde/ and here: http://www.vaisala.com/en/meteorology/products/soundingsystemsandradiosondes/dropsonde/Pages/default.aspx

Investigators

Gerald Heymsfield
NASA Goddard Space Flight Center
Greenbelt, MD 20771

Data and browse files are of the form:

Dyyyymmdd_hhmmss_PQC.eol
NASA_DC8.yyyymmddhhmm.dropsonde_v2_skewT.png
NASA_DC8.yyyymmddhhmm_skewT.png
NASA_DC8.yyyymmdd_hhmmss_Pskewt.png

where

NASA_DC8 = NASA highly modified Douglas DC-8 jetliner
D = one second resolution data files
PQC = post QC data
v2 = processed with version 2 software
yyyymmdd = year, month and day
hhmmss = hour, minutes and seconds
eol = NCAR/Earth Observing Laboratory (EOL) sounding file format
png = Portable Network Graphics

The GRIP DC-8 Dropsonde dataset consists of EOL ASCII text format (.eol) files and skew-T diagram images (.png). The data files contain a header and seventeen columns of high resolution data. Included within the header is detailed project information such as data type, project name, site location. The header also contains sounding information. The skew-T diagrams show the temperature, dewpoint, and vertical wind profiles measured during the flight of the dropsonde. Date, time of release, and mission ID are given in the title of the image. Further information on the data files and skew-T diagrams is provided in readme_GRIP-2010_DC8_dropsondes.pdf.

Our data sets are provided through the NASA Earth Science Data and Information System (ESDIS) Project and the Global Hydrology Resource Center (GHRC) Distributed Active Archive Center (DAAC). GHRC DAAC is one of NASA's Earth Observing System Data and Information System (EOSDIS) data centers that are part of the ESDIS project. ESDIS data are not copyrighted; however, in the event that you publish our data or results derived by using our data, we request that you include an acknowledgment within the text of the article and a citation on your reference list. Examples for general acknowledgments, data set citation in a reference listing, and crediting online web images and information can be found at: http://ghrc.nsstc.nasa.gov/uso/citation.html

References

2011, K. Young, J. Wang, T. Hock and D. Lauritsen, 2011: Genesis and Rapid Intensification Processes (GRIP) 2010 quality controlled dropsonde data set.

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/