amsu_b_ret [ parameter=value ] [ inputfile ... ]
Parameters are rel_humidity, remove_pixels, smooth.
amsu_b_ret uses a global-data based neural network approach to derive humidity profile from AMSU-A and AMSU-B TeraScan datasets (see atovsin). The named input files must be AMSU-B TeraScan datasets output from the ATOVS ingest functions atovsin. Thus, the input filenames must have the suffix ".amsub", meaning AMSU-B sensor datasets. amsu_b_ret also requires the corresponding AMSU-A sensor datasets and the corresponding temperature profiles that are output from the AMSU-A retrieval function amsu_a_ret. The AMSU-A sensor datasets and the temperature files should reside in the same directory as the AMSU-B sensor datasets, and have filename suffixes ".amsua" and ".amsuaret", respectively. Except for these suffixes, their filenames should have the same form as the AMSU-B input filename. Output filenames are generated to have the same form as the input filenames, except with the suffix ".amsubret", meaning AMSU-B retrieval dataset.
The input values to the specific humidity retrieval scheme are the brightness temperatures of five AMSU-B channels, the brightness temperatures of AMSU-A channels 1-8, the AMSU-B sample position and the secant of the satellite viewing angle. The relative humidity and dew-point temperature are derived based on specific humidity and temperature. The output values include the specific humidity and dew-point temperature profiles, the surface specific humidity and dew-point temperature, and optionally, the relative humidity profile and the surface relative humidity. The output profile datasets contain three dimensions: lines, samples and pressure levels. The number of lines depends on the length of the satellite pass being processed. The number of full pixels in a scan line by the AMSU-B is 90, but optionally pixels on each side of the scan can be removed when it is determined that the large viewing angles at both sides of the scan may lead to less retrieval quality. The specific humidity, dew-point temperature, and relative humidity profiles are output for the surface level and the following 21 pressure (mb) levels:
100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 925 950 975 1000
Please note that the the AMSU-B sensor is designed to sound the lower atmospheric levels from the surface to ~500 mb. Above 500 mb the signals received by the sensor are very weak. Cautions should be taken when using the humidity retrieval above 500 mb.
% amsu_b_ret
input file(s) : char(255) ? n15.00022.1619.amsub
Processing n15.00022.1619.amsub: 2000/01/22 16:22:09.509
TDF data set n15.00022.1619.amsubret created.
9696 profiles processed out of 9990 observations.
$TSCANROOT/refdata/bathy/etop05