Effect of surface albedo, water vapour, and atmospheric aerosols on the cloud-free shortwave radiative budget in the Arctic

C. Di Biagio, A. di Sarra, P. Eriksen, S.E. Ascanius, G. Muscari, B. Holben

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Abstract

This study is based on ground-based measurements of downward surface shortwave irradiance (SW), columnar water vapour (wv), and aerosol optical depth (τ) obtained at Thule Air Base (Greenland) in 2007-2010, together with MODIS observations of the surface shortwave albedo (A). Radiative transfer model calculations are used in combination with measurements to separate the radiative effect of A (ΔSWA), wv (ΔSWwv), and aerosols (ΔSWτ) in modulating SW in cloud-free conditions. The shortwave radiation at the surface is mainly affected by water vapour absorption, which produces a reduction of SW as low as -100 Wm-2(-18%). The seasonal change of A produces an increase of SW by up to +25 Wm-2(+4.5%). The annual mean radiative effect is estimated to be -(21-22) Wm-2for wv, and +(2-3) Wm-2for A. An increase by +0.065 cm in the annual mean wv, to which corresponds an absolute increase in ΔSWwvby 0.93 Wm-2(4.3%), has been observed to occur between 2007 and 2010. In the same period, the annual mean A has decreased by -0.027, with a corresponding decrease in ΔSWAby 0.41 Wm-2(-14.9%). Atmospheric aerosols produce a reduction of SW as low as -32 Wm-2(-6.7%). The instantaneous aerosol radiative forcing (RFτ) reaches values of -28 Wm-2and shows a strong dependency on surface albedo. The derived radiative forcing efficiency (FEτ) for solar zenith angles between 55° and 70° is estimated to be (-120.6 ± 4.3) for 0.1 < A < 0.2, and (-41.2 ± 1.6) Wm-2for 0.5 < A < 0.6. © 2012 Springer-Verlag.
Original languageEnglish
Pages (from-to)953 - 969
Number of pages17
JournalClimate Dynamics
Volume39
Issue number3
DOIs
Publication statusPublished - Jul 2012
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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