Presentation on theme: "Changes in clear-sky longwave radiative cooling in the atmosphere 1979-2004 Richard Allan Environmental Systems Science Centre, University of Reading,"— Presentation transcript:
Changes in clear-sky longwave radiative cooling in the atmosphere Richard Allan Environmental Systems Science Centre, University of Reading, UK
Introduction Clear-sky radiative cooling: –radiative convective balance –atmospheric circulation Earths radiation budget –Understand clear-sky budget to understand cloud radiative effect Datasets: –Reanalyses – observing system –Satellites – calibration and sampling GERB comparisons with UKMO forecast model Met Office modelling activities
Datasets used Surface and Top of Atmosphere clear-sky LW fluxes Column integrated water vapour (CIWV) Reanalyses: –ERA-40 ( ) –NCEP-1 ( ) Satellite data –ERBS, ScaRaB, CERES (clear-sky OLR) –SMMR, SSM/I V5 (CIWV) Combination datasets: –SRB Rel. 2( )…reanalysis?
Global variability Ts CIWV LWc SFC ERA40 NCEP SRB
Global variability ERA40 NCEP SRB Surface Net LWc Clear-sky OLR Clear-sky Atmos LW cooling Q LWc
Linear least squares fit Tropical ocean: descending regime DatasetdQ LWc /dTs Slope ERA-403.7±0.5Wm -2 K -1 NCEP4.2±0.3Wm -2 K -1 SRB3.6±0.5Wm -2 K -1 OBS4.6±0.5Wm -2 K -1
Implications for tropical precipitation (GPCP)? ERA40 Q LWc GPCP P OBS Q LWc
Conclusions Intercomparisons of datasets: clear-sky LW at SFC, TOA, ATM Reanalyses: observing system changes Satellites: calibration, sampling Increase in clear-sky LW cooling of atmosphere of ~3-5 Wm -2 K -1 All-sky changes? Models?
Initial comparisons of GERB data with UK Met Office global forecast model Harries et al.(2005) BAMS 86 p.945 Allan et al. (2005) JGR 110, D With thanks to GERB International Science Team including Jacqui Russell (Imperial College, London), Nicolas Clerbaux (RMIB, Belgium)
July 2004 monthly-diurnal mean GERB prelim versionCERES FM1+FM4 OLR Albedo See Jacqui Russells talk for more detailed analysis
Global, 1200 UTC, GERB vs UKMO forecast model Model change GERB change
CLEAR-SKY differences (model minus GERB) Global Ocean, 1200 UTC data Clear-sky OLR Clear-sky Albedo
Current activities at UK Met Office Alejandro Bodas Mark Ringer HadGAM1 – SRB2 SW LW HadGAM1- ISCCP D2 Cloud HadGAM1- 4D DAO CIWV