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GRIP High Altitude MMIC Sounding Radiometer (HAMSR) Table of Contents
Introduction HAMSR is a microwave atmospheric sounder, a small but accurate instrument that is well suited for hurricane and tropical storm studies. It provides measurements that can be used to infer the 3-D distribution of temperature, water vapor, and liquid water in the atmosphere, even in the presence of clouds. Parameters related to scattering from ice particles aloft as well as precipitation can also be inferred. During the GRIP experiment, HAMSR flew on the Global Hawk, a robotic airplane that can fly autonomously to altitudes up to 65,000 feet. CampaignThe 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 life cycle 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. Instrument DescriptionHAMSR is a 25-channel microwave atmospheric sounder operating as a cross-track scanner. It operates in three frequency bands centered around 53, 118 and 183 GHz. HAMSR functionality is similar to AMSU-A/B, but with additional channels. There are three bands: an 8-channel band near 50-GHz, used for primary temperature sounding; a 10-channel band near 118 GHz, used for secondary temperature sounding and assessment of scattering; and a 7-channel band near 183 GHz, used for water vapor (humidity) sounding. The instrument is continuously self-calibrating using internal calibration targets. Radiometric sensitivity at the composite sampling cells provided in the archive is typically 0.1 K and ranges up to 0.25 K for the stratospheric channels. Calibration accuracy is estimated at better than 1 K for temperature sounding and better than 2 K for water vapor sounding. Temperature weighting function peaks are distributed between the surface and the flight altitude. The scan mirror makes a full revolution in a little more than 1 second, for a temporal resolution of one cross-track scan set every 10.4 seconds. During that period it obtains a number of overlapping spatial samples of the scene below and several views of two internal calibration targets. From an altitude of 20 km the scan width is about 40 km wide on the ground with a single field of view of 2 km at nadir. Sampling intervals are 1 km cross-track. Additional information about the HAMSR instrument may be found in the PDF document Hurricane Studies With HAMSR The HAMSR data are in netCDF format. The processing from Level1 (raw instrument telemetry) to Level1B involves conversion of the raw counts to brightness temperature using the two blackbody calibration targets that are viewed through the main reflector each scan. The Level1B data are produced at the sensor resolution and no along-track or cross-track averaging is performed. There is one data file for each of the Global Hawk flights. The File naming convention for the data files is:
where HAMSR identifies the campaign; L1B identifies the product level;yyyymmdd is the year, month and day; hhmmss is hours, minutes, and seconds; vXX is the data version; and the file extension is nc for netCDF file format. For additional information about these L1B data files, refer to: Description of the High Altitude MMIC Sounding Radiometer (HAMSR) Level 1B data format . More information about the netCDF data format can be obtained here: http://www.unidata.ucar.edu/software/netcdf/docs/ Brown, S. T.; Lambrigtsen, B.; Denning, R. F.; Gaier, T.; Kangaslahti, P.; Lim, B. H.; Tanabe, J. M.; Tanner, A. B.; , "The High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle: Instrument Description and Performance," IEEE Transactions on Geoscience and Remote Sensing, in press; doi: 10.1109/TGRS.2011.2125973 Contact InformationThe data producer is:
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