Performance Evaluation of INSAT-3D Derived Outgoing Long Wave Radiation Over India Using Remotely Sensed Observations

This research work focuses on the comparison of Outgoing Long Wave Radiation (OLR) derived from the current operational Indian National SATellite-3D (INSAT-3D) with that from Clouds and the Earth’s Radiant Energy System (CERES), Advanced Very High Resolution Radiometer (AVHRR) and High Resolution Infra-Red Sounder (HIRS) at various temporal scales ranging from daily to monthly. INSAT-3D OLR was averaged over a 2.5° × 2.5° grid to enable comparison between the INSAT-3D, AVHRR, HIRS and CERES OLR. Results show that INSAT-3D derived OLR shows good comparison with HIRS and CERES. AVHRR underestimates, especially over the arid and semiarid regions, which may be attributed to the fact that OLR at the top of atmosphere is also sensitive to the vertical distribution of moisture and thus exclusion of Water Vapor (WV) channel from AVHRR OLR might have resulted in lower values of OLR. Also, the temporal sampling is important as INSAT-3D uses 48 half-hourly observations for computing the daily average, whereas, CERES, HIRS and AVHRR have only 2–3 diurnal samples for daily averages. Quantitative comparison of INSAT-3D OLR at daily scale shows a CC of 0.98, 0.91 and 0.88 with HIRS, CERES and AVHRR, respectively. Positive biases of 1.12 W/m² and 5.93 W/m² in INSAT-3D OLR have been reported with respect to HIRS and AVHRR, respectively. INSAT-3D shows a negative bias of − 5.09 W/m² with CERES observations which is consistent with a previous study. On a monthly scale, INSAT-3D shows excellent agreement with CERES with a bias of 0.45 W/m². The OLR monthly bias from INSAT-3D increases slightly to 7.98 W/m² with respect to AVHRR at a monthly scale. Results reported in this study highlights the applicability of INSAT-3D for various meteorological and climatological studies.