The TOVS Pathfinder Path A data set

TOVS (TIROS Operational Vertical Sounder) is the operational temperature-moisture profile sounding system on the NOAA polar orbiting satellites, comprised of HIRS2, a 20 channel IR sounder, MSU, a 4 channel microwave sounder, and SSU a 3 channel IR pressure modulated stratospheric temperature sounder. The authors have analyzed data from NOAA 9 for Dec. 1985-Dec. 1986 and NOAA 10 for Dec. 1986-Dec. 1988 as part of the Pathfinder project. Products, produced twice daily, on a 1°×1° latitude-longitude grid, include land/ocean surface skin temperature, atmospheric temperature and humidity profile, total atmospheric O₃ column burden, cloud top height and amount, outgoing longwave radiation and longwave cloud radiative forcing, and precipitation estimate. A brief description of the methodology to analyze the data is given, stressing the need for simultaneous IR and microwave observations. Results showing interseasonal and interannual variability and the effects of El Nino are shown. Water vapor distribution is validated compared to radiosondes and shows considerable skill in the interannual variability sense. Cloud fields are validated indirectly by their use in the computation of OLR, which shows almost perfect agreement with the ERBE OLR product. Cloud fields are compared with those produced by ISCCP, and significant qualitative differences in cloud height distribution are shown. Perhaps the most important scientific finding is the very close positive relationship between the distribution of tropical upper tropospheric water vapor and precipitation in space and time