Validation of ground-based microwave radiometer measurements over a tropical coastal station

Ground-based, passive, multi-frequency microwave radiometer profilers (MRP) are very powerful tools to provide vertical profiles of atmospheric parameters under almost all-weather conditions. However, these retrievals are to be validated through other independent estimates, before these are used for scientific studies. Such a validation exercise has been carried out for the MRP, operational at the tropical coastal station, Thiruvananthapuram (TVM), which has been in regular operation since 2010. The validation is done through the inter-comparison of the MRP measured brightness temperature (Tb) with those simulated using microwave radiative transfer scheme that uses collocated and concurrent profiles of temperature and humidity from radiosonde. The analyses have shown a very good correlation (~0.9) with 0.5 K bias for V-band frequency channels while for the K-band frequency channels a 3-5 K bias is seen due to the variability in the water vapour content. The direct comparison of retrieved relative humidity with those derived from radiosonde measurements, yielded good agreement below 8 km altitude.