A BAROmetric Differential Absorption Radar (BARODAR) for surface pressure remote sensing

Spaceborne radar observations with frequencies in the window of the microwave spectrum have been used for acquiring cloud and precipitation measurements at global scale for decades. In recent years differential absorption radar (DAR) concepts have been proposed with frequency of operation in water vapor absorption lines for water vapor profiling and in oxygen absorption lines for surface pressure monitoring.
In this work we will discuss a space-borne concept, BARODAR, proposed in the recent ESA Earth Explorer 12, which aims to provide near global, consistent, and regular observations for determining surface air pressure from space by a novel design of a multi-tone radar operating on the upper wing of the O2 absorption band with tones from 64 to 70 GHz. The radar will be accompanied by a novel Hyperspectral Microwave Radiometer (HYMS) instrument observing the same footprint and providing measurements for determining temperature and water vapour profiles. Simulations of radar vertical profiles based on the output of a state-of-the-art microphysical retrievals applied to the A-Train suite of sensors will be exploited to establish the performance of such a system for surface pressure determination. In particular the identification and quantification of errors introduced by the presence of water vapour, cloud liquid water and rain water and the potential of a correction via the three-tone method will be discussed. Results show that accuracies of the order of few mb are at reach.