HIRS Upper Tropospheric Water Vapor Dataset for Tracking Tropical Convections and Waves

The High-Resolution Infrared Radiation Sounder (HIRS) onboard polar orbiting satellites provide global sounding measurement of the atmosphere. Among the HIRS water vapor channels, channel 12 observes the upper tropospheric water vapor (UTWV). Daily measurements are processed from multiple NOAA and METOP satellites. Intersatellite calibration is performed to bring the data from multi-satellites to a base satellite to form a temporal homogeneous data record. A new dataset, which removes only the clouds in the upper troposphere, is developed for monitoring the variation of water vapor in the upper troposphere. Using the intersatellite calibrated UTWV data, tropical convective events are tracked. Relationship of the UTWV data with several major tropical indexes is examined. The variability of UTWV during major tropical events such as El Niño and La Niña are analyzed. To track and monitor tropical waves, time-longitude section of UTWV data near the equator are examined. The analysis shows that UTWV data have the advantage of providing around-the-globe coverage of equatorial waves. A number of tropical waves, including the Madden-Julian oscillations, Kelvin waves, and equatorial Rossby waves, can be computed by wave-number frequency analysis and monitored on a daily basis. These satellite observations contribute to a better understanding of the tropical variability and the changes in intensity and frequency of tropical convective events.