Spatial and Temporal Variations in Mesoscale Water Vapor Retrieved from TOVS Infrared Radiances in a Nocturnal Inversion Situation

Abstract

Mesoscale moisture fields are retrieved from TOVS (TIROS Operational Vertical Sounder) infrared radiances from two polar-orbiting satellites. A special feature of the retrieval process is the determination of the surface skin temperature independently of the temperature profile above the surface. This allows temperature inversions in retrieved temperature profiles, thereby more closely matching rawinsonde (RAOB) temperature profiles in inversion situations. A modification to the moisture feedback equation is required for such surface temperature inversion cases. Resulting satellite-derived total moisture values are compared both to RAOB-measured moisture at the RAOB scale (>250 km) and to total moisture estimated from surface dew points at the surface weather observation scale (<250 km). One finding is that mesoscale features are detected by the increased density satellite measurements which remain undetected by observations at the RAOB scale. Secondly, differences between satellite-derived and surface-estimated total moisture can indicate vertical moisture extent. Finally, time-changes in the satellite-derived total moisture fields are shown to be similar in pattern to moisture changes estimated from surface observations. Verification of such temporal changes can be found both in comparison to surface-estimated total moisture and by advection of moisture by the 700 mb wind.