Relative humidity distribution from SAPHIR experiment on board Megha‐Tropiques satellite mission: Comparison with global radiosonde and other satellite and reanalysis data sets

Abstract

For better understanding the life cycle of the convective systems and their interactions with the environment, a joint Indo‐French satellite mission named Megha‐Tropiques has been launched in October 2011 in a low‐inclination (20°) orbit. In the present study, we show the first results on the comparison of relative humidity (RH) obtained using a six‐channel microwave sounder, covering from surface to 100 hPa, from one of the payloads SAPHIR (Sounder for Atmospheric Profiling of Humidity in the Inter‐tropical Regions). The RH observations from SAPHIR illustrated the numerous scales of variability in the atmosphere both vertically and horizontally. As a part of its validation, we compare SAPHIR RH with simultaneous observations from a network of radiosondes distributed across the world (±30° latitude), other satellites (Atmospheric Infrared Sounder, Infrared Atmospheric Sounder Interferometer, Constellation Observation System for Meteorology Ionosphere and Climate (COSMIC)), and various reanalysis (National Center for Environmental Prediction (NCEP), European Center for Medium‐Range Weather Forecasts reanalysis (ERA)‐Interim, Modern‐Era Retrospective Analysis for Research and Application (MERRA)) products. Being at a low inclination, SAPHIR is able to show better global coverage when compared to any other existing satellites in the tropical region where some important weather processes take place. A very good correlation is noticed with the RH obtained from a global radiosonde network particularly in the altitude range corresponding to 850–250 hPa, thus providing a valuable data set for investigating the convective processes. In the case of satellite data sets, SAPHIR RH is well comparable with COSMIC RH. Among the reanalysis products, NCEP shows less difference with SAPHIR followed by ERA‐Interim, and the MERRA products show large differences in the middle and upper troposphere.