Publications

Boiyo, R; Kumar, KR; Zhao, TL; Bao, YS (2017). Climatological analysis of aerosol optical properties over East Africa observed from space-borne sensors during 2001-2015. ATMOSPHERIC ENVIRONMENT, 152, 298-313.

Abstract
The present study is aimed at analyzing spatial and temporal characteristics of aerosols retrieved from MODerate resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) sensors over East Africa (EA). Data spanning for a period of 15 years during 2001-2015 was used to investigate aerosol optical depth (AOD(550)), Angstrom exponent (AE(470_660)) and absorption aerosol Index (AAI) over EA and selected locations within EA. Validation results of MODIS Terra versus the Aerosol Robotic NETwork (AERONET) AOD(550) revealed that the former underestimated aerosol loading over the studied regions due to uncertainties in surface reflectance. The annual mean AOD(550), AAI, and AE(470-660) were found to be 0.20 +/- 0.01, 0.81 +/- 0.03, and 1.39 +/- 0.01, respectively with peak values observed during the local dry seasons. The spatial seasonal distributions of mean AOD(550) suggested high (low) values during the local dry (wet) periods. The high AOD values found along the borders of southwest of Uganda were attributed to smoke particles; while higher (lower) values of AE470-660 (AAI) dominated most parts of the study domain. Low AOD (0.1-0.2) centers were located in high-altitude regions with relatively high vegetation cover over western and central parts of Kenya, and central and northern parts of Tanzania. Furthermore, latitudinal and longitudinal gradients in AOD(550) showed a "southern low and northern high" and a "western low and eastern high" profile, respectively during JJA, as other seasons showed heterogeneous variations. Trend analysis revealed a general increase in AOD and AAI and a decrease in AE; while impact factors significantly affected AOD distribution over EA. HYSPLIT back trajectory analyses revealed diverse transport pathways originated from the Arabian Deserts, central Africa, and southwest of Indian Ocean along with locally produced aerosols during different seasons. (C) 2016 Elsevier Ltd. All rights reserved.

DOI:
10.1016/j.atmosenv.2016.12.050

ISSN:
1352-2310