EGU2006 Allan SFC

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1) INTRODUCTION Surface clear-sky net downward longwave radiation (SNLc) is critical for the surface energy balance and the radiative cooling of the atmosphere, thereby representing a crucial parameter determining the global water cycle SNLc is strongly dependent on the column integrated water vapour (CWV) To obtain an accurate estimate of the decadal variability in SNLc over the ocean we utilise a well calibrated record of CWV from satellite microwave instruments and use these as input to an empirical model 6) CONCLUSIONS Variability in the surface net clear-sky radiation balance at the surface (SNLc) is dominated by fluctuations in the total column integrated water vapour (CWV) An empirical estimate of SNLc based on satellite microwave observations of CWV shows excellent agreement with the interannual variability from the NCEP reanalysis The sensitivity, dSNLc/dTs ~ 3 Wm-2K-1, suggests a rapid increase in atmospheric cooling to the surface (surface heating) with warming over the tropical ocean References: Allan, R. P., M.A. Ringer, J.A. Pamment and A. Slingo (2004) J. Geophys. Res., 109, D18107; Henderson, P.W. (2006) PhD thesis, University of Reading; Prata, A.J. (1996) Q. J. R. Meteorol. Soc., 122, p. 1127 CWV (cm)