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Atmospheric clear-sky longwave radiative cooling and precipitation 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
Datasets used Surface and Top of Atmosphere clear-sky LW flux Column integrated water vapour (CWV) Reanalyses: –ERA-40 (1979-2001); NCEP-1 (1979-2004) Satellite data –ERBS, ScaRaB, CERES (clear-sky OLR) –SMMR, SSM/I V5 (CIWV) Combination datasets: –SRB Rel. 2(1983-1994)…reanalysis? –SSM/I, da Silva, ERA40, Prata (1996) surface net LWc IPCC AR4 models
Links to precipitation HadGEM - AMIP
Tropical Oceans 1980 1985 1990 1995 2000 2005 Ts CWV LWc SFC ERA40 NCEP SRB SMMR, SSM/I SSM/I, Prata HadISST
Spurious variability in ERA40 Improved performance in water vapour and clear-sky radiation using 24 hour forecasts
Surface LWc and water vapour dLWc/dCWV ~ 1.5 Wkg -1 ERA40 NCEP dCWV/dTs ~ 3 kgm -2 K -1
Clear-sky OLR with surface temperature: + ERBS, ScaRaB, CERES; SRB Calibration or sampling?
Clear-sky vs resolution
Sensitivity study Based on GERB- SEVIRI and model simulations of OLR and cloud products over ocean: dOLRc/dRes ~0.2 Wm -2 km -0.5 Suggest CERES should be biased low by ~0.5 Wm -2 relative to ERBS
Tropical Oceans Surface Net LWc Clear-sky OLR Clear-sky Atmos LW cooling Q LWc ERA40 NCEP SRB HadISST ERBS, ScaRaB, CERES Derived
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 ERA40 NCEP
Implications for tropical precipitation (GPCP)? ERA40 Q LWc GPCP P OBS Q LWc
IPCC AR4 models: tropical oceans SST CWV Net LWc OLRc
IPCC AR4 models: tropical oceans Q LWc Precip
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?
WGCM CFMIP/IPCC Climate Sensitivity Meeting, Exeter, April 2004 Decadal Variability in Water Vapour Richard Allan, Tony Slingo Environmental Systems Science.
© University of Reading Richard Allan Department of Meteorology, University of Reading Thanks to: Jim Haywood and Malcolm.
Dust and vapour cloud the view Richard Allan Environmental Systems Science Centre, University of Reading, UK Thanks to Tony Slingo, Ruth Comer, Sean Milton,
© University of Reading Chapman Conference on Atmospheric Water Vapor and Its Role in Climate Tropospheric Water Vapour and.
University of Reading Improved understanding of how rainfall responds to a warming world Richard Allan Environmental Systems.
University of Reading 2007www.nerc-essc.ac.uk/~rpa Monitoring satellite observations and model simulations of changes in the atmospheric.
Current Changes in the Tropical Precipitation and Energy Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian Soden, Viju.
IRS2004, Busan, August 2004 Using Satellite Observations and Reanalyses to Evaluate Climate and Weather Models Richard Allan Environmental Systems Science.
Current Changes in Tropical Precipitation Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian Soden, Viju John, William Ingram,
© University of Reading 2009 EUMETSAT Monitoring changes in precipitation and radiative energy using satellite data and.
University of Reading 2007www.nerc-essc.ac.uk/~rpa Present day changes in tropical precipitation extremes in models and observations.
© University of Reading Monitoring and understanding current changes in the global energy & water cycles Richard Allan.
3) Empirical estimate of surface longwave radiation Use an empirical estimate of the clear-sky surface downward longwave radiation (SDLc) to estimate the.
Current Changes in the Global Water Cycle Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian Soden, Viju John, William Ingram,
Contrasting Precipitation Responses to Warming: Models and Satellite Data Richard P. Allan 1 and Brian J. Soden 2 1 Environmental Systems Science Centre,
1 Evaluating water vapour in HadAM3 using 20 years of satellite data Richard Allan, Mark Ringer Met Office, Hadley Centre for Climate Prediction and Research.
Changes in clear-sky longwave radiative cooling in the atmosphere Richard Allan Environmental Systems Science Centre, University of Reading,
NCAS-Climate Talk 15 th January 2010 Current Changes in the Global Water Cycle Richard P. Allan Diffusing slowly to Met Department/NCAS-Climate from ESSC.
Links Between Clear-sky Radiation, Water Vapour and the Hydrological Cycle Richard P. Allan 1, Viju O. John 2 1 Environmental Systems Science Centre, University.
Evaluating the Met Office global forecast model using Geostationary Earth Radiation Budget (GERB) data Richard Allan, Tony Slingo Environmental Systems.
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