The University of Wisconsin TOVS package has been implemented as part of the TeraScan software system. The TOVS Application Package (TAP) includes a physical retrieval algorithm (physical solution of the radiative transfer equation) that produces temperature, moisture, and thermal wind profiles at a horizontal resolution of about 75 km from the HIRS (infrared) and MSU (microwave) sounding radiance observations. In addition, total ozone concentration and surface skin temperature are calculated. Ingest, calibration, and earth-location of direct readout data is performed by tipin, preing, and ingtov, respectively. Preprocessing of the data is accomplished in tovpre, and soundings are generated with tovret. tovscdf converts University of Wisconsin output files into TeraScan datasets.
The TeraScan function tovsproc is a script that relieves the user from having to type in the sequence of TOVS commands by combining them into one script command.
The files supplied contain main programs, associated subroutines, and supporting quasi-permanent data that are necessary for processing HIRS and MSU data. The principal processing tasks can be divided into three categories: ingest, preprocessing, and retrieval.
The function of the ingest programs is to produce calibrated, earth-located HIRS and MSU radiometric measurements from NOAA satellite data obtained on-site by direct downlink from the spacecraft. (For information on real-time data transmission from the TIROS-N/NOAA series satellites, refer to Lauritson et al., 1979). preing reformats the direct readout data and ingtov calibrates and earth-locates the HIRS and MSU data. tovpre performs limb corrections and reformats the dataset for the retrieval software.
The preprocessing is done in four parts. They are:
a. Correct MSU for:
(1) antenna pattern (side lobes)
(2) limb effects (slant path)
(3) surface reflectivity
(4) liquid water (cloud/precip) attenuation
b. Correct HIRS for:
(1) fluorescence @ 2360 cm-1 (if daytime)
(2) limb effects
(3) water-vapor attenuation (window channels)
(4) reflected sunlight @ 2500 cm-1 (if daytime)
c. Collocate MSU and HIRS by interpolating MSU to
HIRS scan pattern.
d. Output to disk in forms convenient for:
(1) imaging (all data for one parameter
contiguous on disk)
(2) sounding (all data for one scan spot
contiguous on disk)
Finally, the retrieval programs are contained in tovret. It is here that vertical profiles of atmospheric temperature, humidity, geopotential height, thermal wind are determined from the preprocessed HIRS and MSU data.
A few miscellaneous programs are included in the TAP for manipulating the profiles produced by the retrieval programs. They are:
a. filret eliminates soundings of questionable reliability by objective analysis of differences between infrared and microwave retrievals for the same earth location, and of variability in HIRS longwave window and water vapor channels.
b. winret determines geostrophic winds for "good" soundings in the retrieval file, by least-squares fit of height fields.
The TAP uses the Simultaneous Physical Solution method (Smith et al., 1985) as the solution to the radiative transfer equation. Briefly, the method entails:
Each step of the TAP package requires one or more input files and produces one or more output files. The names of these files depend on the particular processing step and are listed with each function description. To uniquely identify each important intermediate file and the final output file a one character identifier is appended to the name. This character can be a number [0-9] or a letter [A-Z].
Smith, W.L., H.M. Woolf, C.M. Hayden, A.J. Schreiner, 1985: The simultaneous retrieval export package. Second International TOVS Study Conference, Igls, Austria, February 18- 22, 1985.
Lauritson, L., G.J. Nelson and F.W. Porto, Data Extraction and Calibration of TIROS- N/NOAA Radiometers, Tech Memo, NESS 107, Natl. Oceanic and Atmos. Admin, Boulder, Colo., 1979.
Last Update: $Date: 2001/05/16 18:33:03 $