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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 ( ); NCEP-1 ( ) Satellite data –ERBS, ScaRaB, CERES (clear-sky OLR) –SMMR, SSM/I V5 (CIWV) Combination datasets: –SRB Rel. 2( )…reanalysis? –SSM/I, da Silva, ERA40, Prata (1996) surface net LWc IPCC AR4 models
Links to precipitation HadGEM - AMIP
Tropical Oceans 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?
Changes in clear-sky longwave radiative cooling in the atmosphere Richard Allan Environmental Systems Science Centre, University of Reading,
Changes in Water Vapour, Clear-sky Radiative Cooling and Precipitation Richard P. Allan Environmental Systems Science Centre, University of Reading, UK.
Dust and vapour cloud the view Richard Allan Environmental Systems Science Centre, University of Reading, UK Thanks to Tony Slingo, Ruth Comer, Sean Milton,
ESSC Seminar, October 18, 2007© University of Reading 2007www.reading.ac.uk Intensification of the tropical hydrological cycle? Richard P. Allan Environmental.
IRS2004, Busan, August 2004 Using Satellite Observations and Reanalyses to Evaluate Climate and Weather Models Richard Allan Environmental Systems Science.
University of Reading 2007www.nerc-essc.ac.uk/~rpa Observed and simulated changes in water vapour, precipitation and the clear-sky.
3) Empirical estimate of surface longwave radiation Use an empirical estimate of the clear-sky surface downward longwave radiation (SDLc) to estimate the.
Trends in Water Cycle meeting, Paris, November 2004 Cloud and water vapour variability: models, reanalyses and observations Richard P. Allan and Tony Slingo.
University of Reading 2007www.nerc-essc.ac.uk/~rpa Present day changes in tropical precipitation extremes in models and observations.
RMS 18 th June 2003 Evaluating moisture in the Hadley Centre Climate Model using 20 years of satellite data Richard Allan Environmental Systems Science.
University of Reading 2007www.nerc-essc.ac.uk/~rpa Monitoring satellite observations and model simulations of changes in the atmospheric.
University of Reading 2007www.nerc-essc.ac.uk/~rpa Surface radiative fluxes: comparison of NWP/Climate models/reanalyses with.
IPCC Workshop on Climate Sensitivity, Paris, July 2004 Exploiting observations of water vapour to investigate simulations of water vapour feedback processes.
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.
1 03/0045a © Crown copyright Evaluating water vapour in HadAM3 with 20 years of satellite data Richard P. Allan Mark A. Ringer Met Office, Hadley Centre.
SYSTEMATIC BIASES 3-hourly comparisons of top of atmosphere radiation from GERB and the Met Office global forecast model Systematic biases in model fluxes.
WGCM CFMIP/IPCC Climate Sensitivity Meeting, Exeter, April 2004 Decadal Variability in Water Vapour Richard Allan, Tony Slingo Environmental Systems Science.
EUMETSAT 2006 Helsinki Exploitation of GERB/SEVIRI data for evaluation of the Met Office global forecast model Richard Allan, Tony Slingo Environmental.
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.
© University of Reading 2009 EUMETSAT Monitoring changes in precipitation and radiative energy using satellite data and.
Current Changes in the Global Water Cycle Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian Soden, Viju John, William Ingram,
GERB/CERES Meeting 2006 Exeter Evaluation of clouds and radiation in the Met Office global forecast model using GERB/SEVIRI data Richard Allan, Tony Slingo.
Current Changes in the Tropical Precipitation and Energy Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian Soden, Viju.
© University of Reading Monitoring and understanding current changes in the global energy & water cycles Richard Allan.
The atmospheric hydrological cycle and climate feedbacks: recent advances Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian.
University of Reading Improved understanding of how rainfall responds to a warming world Richard Allan Environmental Systems.
Exploiting observations to seek robust responses in global precipitation Richard P. Allan Department of Meteorology, University of Reading Thanks to Brian.
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.
Evaluating the Met Office global forecast model using Geostationary Earth Radiation Budget (GERB) data Richard Allan, Tony Slingo Environmental Systems.
1 Using Reanalyses in combination with Earth Radiation Budget data to evaluate climate model simulated cloud radiative properties Richard P. Allan, Tony.
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