Evaluation of MODIS/CERES downwelling shortwave and longwave radiation over global tropical oceans

Abstract

In the present work, we have evaluated the satellite estimated daily downwelling shortwave (QI) and Longwave (QA) radiation from Moderate Resolution Imaging Spectrometer (MODIS) /Clouds and the Earth's Radiant Energy System (CM) with moored buoy observations of Global Tropical Moored Buoy Array (GTMBA) during 2001-2009. The global observed mean of QI and QA in GTMBA (CM) are 228 (233) W/m2 and 410 (405) W/m2 respectively. The mean QI shows a positive bias (~3- 7 W/m2) whereas QA underestimates with a mean negative bias of ~3-6 W/m2 in the tropical Pacific, Atlantic and Indian Ocean. CM underestimates the buoy observed variability in both QI and QA in all the tropical oceans. The correlation coefficient (CC) values in QI (Qa) are 0.79(0.88) 0.79(0.84) and 0.81(0.94) over the Pacific, Atlantic and Indian ocean respectively. The Root Mean Square Error (RMSE) values in QI ranged between 35-43 W/m2 with lowest values in the Atlantic Ocean and highest in the Indian Ocean. The RMSE values in QA are less as compared to QI and it is ~9 W/m2 in all the tropical ocean. The spatial distributions of QI and QA shows seasonality with lower and higher values coinciding with the Inter Tropical Convergence Zone(ITCZ) locations in the QI and QA.