Investigations of MODIS AOD and cloud properties with CERES sensor based net cloud radiative effect and a NOAA HYSPLIT Model over Bangladesh for the period 2001-2016

摘要

The present study investigates the spatiotemporal characteristics of aerosol optical depth (AOD), cloud properties, and TOA (Top Of Atmosphere) Net Cloud Radiative Effect (Net CRE) using MODIS (Moderate Resolution Imaging Spectroradiometer) Terra and CERES (Clouds and the Earth's Radiant Energy System) products over Bangladesh for the period 2001-2016. This study also explores the backward trajectory using a HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model from the National Oceanic and Atmospheric Administration (NOAA) to discover the origins of air masses. Results show annual values of AOD (0.55), Cloud Fraction (CF, 0.66), CER (Cloud Effective Radius, 14.89), COT (Cloud Optical Thickness, 15.25), CTP (Cloud Top Pressure, 639.17), CTT (Cloud Top Temperature, 262.52), WV (Water Vapor, 4.48), and Net CRE (-13.06) over Bangladesh. A seasonally peak is recorded for AOD (0.64) in MAM while for CF (0.96), CER (17.24), COT (21.12), WV (6.86), and Net CRE (-34.44) the peak is in JJA, and for CTP (884.06) and CTT (28417) it is in DJF. By monthly the peak is recorded in June for AOD (0.73) and COT (24.86); for CER (17.87), WV (7.26), and Net CRE (-45.38) it is in July; for CF (0.97) it is in July/August; CTP (900.89) and for CTT (285.75) it is in February. Regression analysis shows annual increasing trends for AOD, CF, WV, COT, CTP, and CTT with negative trends for CER and Net CRE. AOD shows increasing trends in all seasons, whereas CF, CER and COT show increasing trends in DJF and MAM only. CTP and CTT show increasing trends in JJA and SON. WV shows an increasing trend in MAM, JJA, and DJF, whereas Net CRE shows an increasing trend in MAM and SON. Relationship study provides a better conclusion of AOD and cloud interaction based on the analysis of positive and negative correlation values over the study region. The backward trajectory indicated that the air masses originated from the Bay of Bengal, India, Nepal, Pakistan, and Iran. This study may be considered as a base document for further study on aerosols over Bangladesh using climate model simulation for the projection period.