1. Data Set Information
This data set contains the TIROS Operational Vertical Sounder (TOVS) level 3 geophysical parameters derived using the physical retrieval method of Susskind et al. (1984). The data were processed by the Satellite Data Utilization Office of the Goddard Laboratory for Atmospheres at NASA/GSFC. This method, which is model- anda priori data-dependent, is designated as the so-called Path A scheme by the TOVS Pathfinder Science Working Group. The data are archived at the Goddard Distributed Active Archive Center (DAAC).
The primary goal of Pathfinder is the production of consistently processed, long-term data sets for use in global change studies. TOVS Pathfinder is one of several Pathfinder studies initiated by NOAA and NASA (the others being AVHRR, GOES, and SSM/I Pathfinders). As a first step in the processing, a common benchmark period was selected to facilitate the analysis and intercomparison of geophysical fields derived from the various Pathfinders. The benchmark period covers the time period April 1987 through November 1988.
The 20-channel High resolution Infrared Radiation Sounder 2 (HIRS/2) and the 4-channel Microwave Sounding Unit (MSU) aboard the NOAA-xx series of Polar Orbiting Satellites are used to produce global fields of the 3-dimensional temperature-moisture structure of the atmosphere. In addition to profiles of temperature and moisture, the HIRS2/MSU data are used to derive surface skin temperature, sea surface temperature, outgoing longwave radiation, cloud fraction, cloudtop height, total integrated column ozone and precipitation estimates.
The Path A system steps through an interactive forecast-retrieval- analysis cycle. In each 6-hour synoptic period, a 2nd order General Circulation Model (Takacs et al., 1994) is used to generate the 6-hour forecast fields of temperature and humidity. These global fields are used as the first guess for all soundings occurring within a 3-hour time window centered upon the forecast time. These retrievals are then assimilated with all available in situ measurements (such as radiosonde and ship reports) in the 6-hour interval using an Optimal Interpolation (OI) analysis scheme developed by the Data Assimilation Office of the Goddard Laboratory for Atmospheres. This analysis is then used to specify the initial conditions for the next 6-hour forecast, thus completing the cycle.
TOVS (before AIRS) was the only long-term source of high resolution global information pertaining to the temperature and moisture structure of the atmosphere. Because similar HIRS/2 and MSU instrumentation has flown on operational satellites from 1979 to the present, data from these instruments can make an important contribution to the understanding of the variability of atmospheric and surface parameters as well as the correlations between spatial variations of atmospheric and surface quantities. In addition, the data can potentially be used to identify and monitor trends in temperature, moisture, clouds, radiation, and precipitation, provided satellite drifts and cross-calibration of different satelites are taken into account. The full TOVS Pathfinder data set, of which the NOAA-10 benchmark period is a subset, are processed in a consistent manner and as such will be useful for all of the applications listed above.
The full directory tree on the FTP server reflects which satellites were used in the Path-A processing, and thus have the patterns:
TOVSA [D,5,M] [NT,NF,NG,NH,ND]
[D,5,M] - stands for Daily, 5-day (pentad), and Monthly
[NT,NF,NG,NH,ND] - which satellite, correspondingly: TIROS-N, NOAA-F,G,H,D (see history)