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Effect of aerosols on evapo-transpiration

Murthy, BS and Latha, R and Kumar, Manoj and Mahanti, NC (2014) Effect of aerosols on evapo-transpiration. Atmospheric Environment, 89. pp. 109-118.

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Abstract

Aerosol direct radiative forcing (ARF) at surface is estimated from instantaneous, simultaneous observations of global radiation and aerosol optical depth (AOD) during winter, pre-monsoon and monsoon seasons over a tropical Indian station at the south-eastern end of Indo Gangetic basin. A comparison of observed and model derived ARFs is made and possible reasons for mismatch are discussed. Aerosol-induced reduction in solar visible (0.4-0.7μm) spectrum energy (SWvis), contributing 44 to total broad band (0.3-3.0μm) energy (SW), and its effect on surface energy fluxes are discussed in this study. Aerosols on an average reduce SWvis at surface by ~27. SWvis reduces by 14.5Wm-2 for a 0.1 increase in AOD when single scattering albedo (SSA) is 0.979 where as it reduces by 67.5Wm-2 when SSA is 0.867 indicating the significant effect of absorbing aerosols. Effect of ARF on net radiation, Rn, sensible heat flux, H and latent heat flux/evapo-transpiration, LE are estimated using the observed ratios of Rn/SW, H/Rn and LE/Rn, having reasonably good correlation. Observed Rn/SW varies between 0.59 and 0.75 with a correlation of 0.99 between them. LE, calculated by energy balance method, varies from 56 to 74 of Rn but with a lesser correlation, the possible reasons are discussed. For a given ARF, LE decreases by ~14 and Rn by ~15 with respect to observed LE and Rn respectively. The reduction in LE increases from 37 to 54 of ARF when LE increases from 220Wm-2 to 440Wm-2, suggesting that wet soil induces relatively larger reduction in evaporation. The results agree with earlier model sensitivity studies that Rn reduces more with increase in aerosol absorption which is compensated by proportionate reductions in H and LE depending on soil and atmospheric conditions.

Item Type: Article
Additional Information: Copyright of this article belongs to Elsevier
Uncontrolled Keywords: Aerosol direct radiative forcing; Aerosol optical depths; Aerosol radiative forcing; Atmospheric conditions; Radiation budget; Short-wave radiation; Simultaneous observation; Single scattering albedo, Atmospheric aerosols; Atmospheric radiation; Atmospheric thermodynamics; Heat flux; Solar radiation, Transpiration, aerosol; energy balance; energy flux; evapotranspiration; numerical model; radiative forcing; sensible heat flux; shortwave radiation, aerosol; aerosol optical depth; albedo; article; chemical parameters; energy balance; environmental impact; evapotranspiration; greenhouse gas; optical depth; photosynthesis; priority journal; radiation; radiative forcing; seasonal variation; single scattering albedo; spectrum, Gangetic Plain
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 23 May 2015 08:59
Last Modified: 23 May 2015 08:59
URI: http://moeseprints.incois.gov.in/id/eprint/884

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