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Performance of WRF-Chem over Indian region: Comparison with measurements

Govardhan, Gaurav and Nanjundiah, Ravi S and Satheesh, SK and Krishnamoorthy, K and Kotamarthi, VR (2015) Performance of WRF-Chem over Indian region: Comparison with measurements. In: JOURNAL OF EARTH SYSTEM SCIENCE, 124 (4). pp. 875-896.

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Official URL: http://dx.doi.org/10.1007/s12040-015-0576-7

Abstract

The aerosol mass concentrations over several Indian regions have been simulated using the online chemistry transport model, WRF-Chem, for two distinct seasons of 2011, representing the pre-monsoon (May) and post-monsoon (October) periods during the Indo-US joint experiment `Ganges Valley Aerosol Experiment (GVAX)'. The simulated values were compared with concurrent measurements. It is found that the model systematically underestimates near-surface BC mass concentrations as well as columnar Aerosol Optical Depths (AODs) from the measurements. Examining this in the light of the model-simulated meteorological parameters, we notice the model overestimates both planetary boundary layer height (PBLH) and surface wind speeds, leading to deeper mixing and dispersion and hence lower surface concentrations of aerosols. Shortcoming in simulating rainfall pattern also has an impact through the scavenging effect. It also appears that the columnar AODs are influenced by the unrealistic emission scenarios in the model. Comparison with vertical profiles of BC obtained from aircraft-based measurements also shows a systematic underestimation by the model at all levels. It is seen that concentration of other aerosols, viz., dust and sea-salt are closely linked with meteorological conditions prevailing over the region. Dust is higher during pre-monsoon periods due to the prevalence of north-westerly winds that advect dust from deserts of west Asia into the Indo-Gangetic plain. Winds and rainfall influence sea-salt concentrations. Thus, the unrealistic simulation of wind and rainfall leads to model simulated dust and sea-salt also to deviate from the real values; which together with BC also causes underperformance of the model with regard to columnar AOD. It appears that for better simulations of aerosols over Indian region, the model needs an improvement in the simulation of the meteorology.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the INDIAN ACAD SCIENCES, C V RAMAN AVENUE, SADASHIVANAGAR, P B #8005, BANGALORE 560 080, INDIA
Keywords: Aerosols; black carbon; modelling
Department/Centre: Division of Mechanical Sciences > Divecha Centre for Climate Change
Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Depositing User: Id for Latest eprints
Date Deposited: 31 Jul 2015 05:54
Last Modified: 03 Nov 2016 07:55
URI: http://eprints.iisc.ac.in/id/eprint/51924

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