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Aerosol and cloud feedbacks on surface energy balance over selected regions of the Indian subcontinent

Urankar, G and Prabha, TV and Pandithurai, G and Pallavi, P and Achuthavarier, D and Goswami, BN (2012) Aerosol and cloud feedbacks on surface energy balance over selected regions of the Indian subcontinent. Journal of Geophysical Research D: Atmospheres, 117 (4).

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Abstract

We investigate aerosol and cloud forcing on the surface energy balance over selected regions in India. Four regions were selected with different surface characteristics and have considerable differences in the long-term trends and seasonal distribution of clouds and aerosols. These regions are described as (1) northern semiarid, (2) humid subtropical, (3) populated central peninsula, and (4) northeast monsoon impacted. Modern Era Retrospective-analysis for Research and Applications (MERRA) data and Climate Forecast System Reanalysis version 2 (CFSR) data are used in this study. An intercomparison of cloud fractions from both data sets shows that CFSR systematically underestimates high-cloud fraction during premonsoon and monsoon seasons. However, there are fewer low-cloud fraction biases. The positive temporal trend over 31years (1979-2009) from MERRA in high clouds is greater than that of low clouds. This is due to positive anomalies in the cloud ice and supercooled liquid water content in MERRA. Biases in the radiative fluxes and surface fluxes show a strong relationship (correlations exceeding 0.8) with cloud fraction biases, more so for the high clouds. During the premonsoon season, aerosol forcing causes a change in surface shortwave radiation of -24.5, -25, -19, and -16Wm -2 over regions 1 -4, respectively. The corresponding longwave radiation decrease is -9.8, -6.8, -4.5, and -1.9Wm -2 over these same regions, respectively. The maximum surface shortwave reduction due to clouds, which is observed during the monsoon season, is -86, -113, -101, and -97Wm -2 for these same regions, respectively. A decreasing trend in the boundary layer height is noticed both in MERRA and CFSR. The variation in the Bowen ratio and its relation to aerosol and cloud effect anomalies are also discussed.

Item Type: Article
Additional Information: Copyright of this article belongs American Geophysical Union.
Uncontrolled Keywords: Aerosol forcing; Boundary layer heights; Bowen ratio; Climate forecasts; Cloud effects; Cloud forcing; Cloud fraction; Data sets; Intercomparisons; Long-term trend; Long-wave radiation; Monsoon season; Northeast monsoon; Pre-monsoon; Radiative fluxes; Reanalysis; Research and application; Seasonal distributions; Short-wave radiation; Supercooled liquid water; Surface characteristics; Surface flux; Temporal trends, Atmospheric thermodynamics; Energy balance; Interfacial energy; Surface chemistry, Atmospheric aerosols, aerosol composition; Bowen ratio; cloud cover; data set; energy budget; long-term change; longwave radiation; seasonal variation; shortwave radiation; supercooling; surface energy, India
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 21 Dec 2013 06:28
Last Modified: 21 Dec 2013 06:28
URI: http://moeseprints.incois.gov.in/id/eprint/518

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