Ground- and Space-Based Temperature and Humidity Retrievals: Statistical Evaluation

Abstract

A near-real-time integrated temperature and water vapor sounding system has been designed and in operation since June 1993. It combines hourly data from the ground-based radio acoustic sounding system (RASS), a two-channel microwave radiometer, standard surface meteorological instruments, a lidar ceilometer, and the Aerodynamic Research Incorporated Communication, Addressing and Reporting System aboard commercial airlines with space-based data from the TIROS-N Operational Vertical Sounder (TOVS). The physical retrieval algorithm provided by the International TOVS Processing Package is used for combining the ground- and space-based temperature and humidity profiles. The first-guess profiles of temperature and humidity required by the physical retrieval algorithm arc obtained by using a statistical inversion technique and the ground-based remote sensors measurements. Statistical error estimates are presented for the hourly. near-real-time, ground-, and space-based retrieved temperature and humidity profiles based on 119 soundings collected during a two-month-long experiment conducted at Platteville, Colorado, during February and March 1994. Radiosonde data collected by the Environmental Technology Laboratory and the Winter Icing and Storms Program in Platteville and the National Weather Service in Denver, Colorado, are used for comparison. The comparison showed excellent agreement between retrieved and radiosonde soundings. Retrieved temperature profiles show better performance than the retrieved humidity profiles because of the high vertical resolution of the RASS measurements. It is suggested that adding more information from the new individual remote sensors as they develop, through the technique used here, would lead to further profiling improvements.