Land surface characterization of microwave emissivities at MADRAS payload frequencies:
The microwave payload MADRAS (Microwave Analysis and Detection of Rain and Atmospheric Systems) on-board MT is a dual (H and V) polarization microwave imager measuring radiance at five frequencies (18.7, 23.8, 36.5, 89 and 157 GHz), except for 23.8 GHz (V only). It is a conical scanning (~ 53° incidence angle), self-calibrating, total power radiometer. The data from MT-MADRAS has been utilized for studying the terrain characteristics using brightness temperature (TB) data, estimating the surface emissivity using an in-house developed microwave RT algorithm, and generating surface emissivity maps for all the MADRAS channels. Comparison of MT-derived emissivity has been conducted with those from concurrent and collocated TRMM Microwave Imager (TMI) observations on global basis, with the limited data available.
Utility of SAPHIR payload data for deriving Upper tropospheric humidity (UTH):
Upper Tropospheric Humidity (UTH) has been derived using a ‘brightness temperature transformation’ method from the humidity sounder channels of SAPHIR payload aboard Megha-Tropiques (MT). These channels are very close to the water vapour absorption peak at 183.31 GHz. The channels at channel 183±0.2 GHz enables retrieval of humidity up to the highest altitude possible with the present nadir looking microwave humidity sounders. Transformation coefficients for the first three channels for all the incidence angles have been derived and are used to convert brightness temperatures to free/upper tropospheric humidity at different pressure levels. UTH over the tropical belt has been studied taking advantage of the first humidity product with high spatial and temporal resolution.
Megha Tropiques Project: Cloud Radiative Forcing Using ScaRaB: