TITLE: POES NOAA AVHRR AMSU-A Data [NCAR/EOL] CONTACTS: Steve Williams NCAR/EOL P.O. Box 3000 Boulder, CO 80307-3000 phone: 303-497-8164 email: sfw@ucar.edu 1.0 DATA SET OVERVIEW This data set contains AMSU-A (Advanced Microwave Sounding Unit-A) data from the NOAA POES satellites (K/L/M/N). These data were retrieved from the NOAA CLASS archive. The data are in Level 1-b format and cover the T-REX period (1 March to 30 April 2006). They cover the region from 34-40 N and 115-126 W. 2.0 INSTRUMENT DESCRIPTION Complete information on the NOAA POES AMSU-A instumentation is available from the NOAA KLM User's Guide: http://www2.ncdc.noaa.gov/docs/klm/ The Advanced Microwave Sounding Unit-A (AMSU-A) is part of the ATOVS instrument suite flown onboard the NOAA KLM series of satellites. The AMSU-A is a multi-channel microwave radiometer used for measuring global atmospheric temperature profiles and for gathering information on atmospheric water in all of its forms, save small ice particles which are transparent at microwave frequencies. AMSU-A is a cross-track, line-scanned instrument designed to measure scene radiances in 15 discrete frequency channels. These measurements permit the calculation of the vertical temperature profile from about 3 millibars (~45 km) to the Earth's surface. At each channel frequency, the antenna beamwidth is a constant 3.3 degrees (at the half power point). Thirty contiguous scene resolution cells are sampled in a stepped-scan fashion every eight seconds with each scan covering 50 degrees on each side of the subsatellite path. The scan pattern and geometric resolution translate to a 50 km diameter cell at nadir and a 2,343 km swath width from the 833 km nominal orbital altitude. The AMSU-A system is implemented in two separate modules: the AMSU-A1 and AMSU-A2. AMSU-A1 consists of 12 V-band channels (3 through 14) and one W-band channel (15). This module provides a complete and accurate vertical temperature profile of the atmosphere from the Earth's surface to a height of approximately 45 km. AMSU-A2 contains the two lower frequencies (K-band channel 1 and Ka-band channel 2). This module is used to study atmospheric water in all of its forms with the exception of small ice particles. 3.0 DATA COLLECTION AND PROCESSING NCAR/EOL conducted no processing or quality control on these data. The NOAA ATOVS processing flow begins with sensor data receipt by the Command and Data Acquisition (CDA) stations where the data are re-broadcast via communications satellites to NOAA/NESDIS in Suitland, MD where they are processed. Earth location and calibration data are appended, but not applied, to the data as part of the Level 1b processing. The earth locations are computed for specific pixels using the data time corrected for clock drift, if any. Shortly after arriving at NOAA/NESDIS, the data are made available at the Comprehensive Large Array-data Stewardship System (CLASS). Global coverage is available for the AMSU-A data which have an Instantaneous Field of View (IFOV) of approximately 3.3 degrees. From an altitude of 833 kilometers, this translates into a ground IFOV encompassing an area of 48.05 kilometers in diameter at nadir on the Earth. At scan end, a 149.1 km cross-track by 79.4 km along-track footprint is registered, again assuming a nominal altitude of 833 km. At the equator, the 96.66 degree scan equates to a swath width of 2,226.8 km to the far edge of the outer FOV centered on the subsatellite track. The instrument is automatically calibrated each data cycle by measuring both warm and cold calibration targets. Once every 8 seconds, the AMSU-A measures 30 Earth views, the space view twice and the internal blackbody target twice. 4.0 DATA FORMAT AND FILE NAMING 4.1 File Naming conventions NSS.AMAX.NN.D06118.S2032.E2227.B0484243.GC.L7193461 where: AMAX is the data type (AMSU-A) NN is the satellite (NOAA-N) D06118 is the year (06) and Julian day (118) S2032 is the scan start time (UTC) E2227 is the scan end time (UTC) 4.2 Data Format These data are in Level 1-b format. Complete information on the NOAA POES AMSU-A format is available from the NOAA KLM User's Guide: http://www2.ncdc.noaa.gov/docs/klm/ 5.0 DATA REMARKS 6.0 REFERENCES None.