Towards the Temperature Retrieval by Using Airborne Microwave Radiometer Data

Abstract

Atmospheric temperature is a key geophysical parameter when dealing with the atmosphere in areas such as climatology and meteorology. In general, thermal emissions of molecular lines (e.g. oxygen, carbon dioxide) can be used for the determination of the temperature profile. The superheterodyne radiometer MTP (Microwave Temperature Profiler) passively detects thermal emission from oxygen lines at a selection of frequencies between 55--60 GHz by scanning the atmosphere from near zenith to near nadir in the flight direction. The MTP instrument was designed to observe the vertical temperature distribution over the upper troposphere and lower stratosphere (UTLS) with a good temporal and spatial resolution. The instrument was originally developed at NASA's JPL and has been recently flown on DLR's Falcon and HALO research aircrafts. To estimate the temperature profile from microwave measurements (e.g. provided by MTP), the retrieval algorithm TIRAMISU (Temperature Inversion Algorithm for Microwave Sounding) has been developed at DLR and is currently used to conduct the data processing of the MTP measurements. This study performs the retrievals from the MTP data with a focus on the ML-CIRRUS mission. The corresponding retrieval performance is investigated by associated error characterization and external comparisons with other ground-based and satellite observations. These observations are important to resolve a variety of phenomena in the UTLS region and to potentially improve the temperature spaceborne soundings.