Singh, Sachchidanand and Lodhi, Neelesh K. and Mishra, Amit Kumar and Jose, Sandhya and Kumar, S. Naresh and Kotnala, R. K. (2018) Assessment of satellite-retrieved surface UVA and UVB radiation by comparison with ground-measurements and trends over Mega-city Delhi. Atmospheric Environment, 188. pp. 60-70. ISSN 1352-2310

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Abstract

Solar UV radiation reaching the Earths surface is known to have various effects on human health and on the ecosystem. Ground-based measurements of surface UV radiation are spatially sparse and in many cases do not provide long time series. Higher spatial coverage can be provided by measurements from satellite based instruments, but these measurements need to be compared to ground-based measurements of sufficient quality before they can be used in health and ecosystem applications. Here, we compare the measurements of surface solar UV radiation in UVA (315-400 nm) and UVB (280-315 nm) bands with the satellite retrievals (CERES) and validate the latter at an urban location, Delhi, India. We have also used MODIS-retrieved aerosol optical depth (AOD) and cloud optical depth (COD) data to see the effect of atmospheric opacity on UV radiation. Ground based measurements of UVA and UVB were performed from 01 October, 2012 to 30 September, 2015: Correlations between daily surface measurements and CERES-derived surface UV fluxes showed very good agreement (r similar to 0.92-0.93) over Delhi. We found a negative correlation between UV fluxes and AOD over Delhi during all seasons. A unit increase in AOD leads to a decrease of similar to 4-5 Wm(-2) in UVA and similar to 0.09-0.14 Wm(-2) in UVB over Delhi. The trend analysis from monthly mean CERES-derived UV fluxes for 17 years data reveals that UVA and UVB are decreasing similar to 0.07 Wm(-2) yr(-1) and 0.003 Wm(-2) yr(-1), respectively with AOD increase (similar to 0.005 yr(-1)) over Delhi. The simultaneous increase in aerosol loading with decrease in UV fluxes at the surface may be explained as a masking effect of ever increasing pollution on surface UV radiation over Delhi. Our results show similar to 10% and similar to 20% decrease (with respect to mean) in UVA and UVB surface fluxes, respectively during last 17 years.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s Elsevier.
Subjects:	Earth Sciences Meteorology & Atmospheric Sciences
Divisions:	UNSPECIFIED
Depositing User:	Users 27 not found.
Date Deposited:	17 Dec 2019 08:27
Last Modified:	17 Dec 2019 08:27
URI:	http://npl.csircentral.net/id/eprint/3799

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