Apresentação em tema: "Down-welling Long-wave Fluxes at the Surface"— Transcrição da apresentação:
1 Down-welling Long-wave Fluxes at the Surface Thermal RadiationDown-welling Long-wave Fluxes at the SurfaceIsabel F. Trigo
2 MSG-based Radiation Products Down-welling Long-wave Flux (DSLF)DefinitionAlgorithm BasisThe LSA SAF DSLF product from MSGValidation
3 ? ? Radiation Budget Earth Surface 30% 23% 47% Thermal Radiation 90%4%47%Thermal RadiationSolar RadiationEarth SurfaceShort-Wave Net RadiationLossGain?Long-Wave Net RadiationLossGain?Adapted from K. Trenberth, J. Fasullo, and J. Kiehl.
4 Radiation Budget Earth Surface X X Thermal Radiation Solar Radiation 30%23%7%Thermal RadiationSolar Radiation90%4%Earth SurfaceShort-Wave Net RadiationLossGainXLong-Wave Net RadiationLossGainXAdapted from K. Trenberth, J. Fasullo, and J. Kiehl.
5 Surface Down-welling Long-Wave Radiation Down-welling Long-wave Fluxes at the SurfaceLong-wave Radiation reaching the Surface:Essentially emitted by the lowest 100 m of the atmosphereEmitted by the atmosphere, RaIt is controlled byconcentration of abosrbing gasesCO2, CH4, H2O, ...presence of clouds, clouds phasetemperature profile & temperature of cloud base....Reflected by the surface, RreflEmitted by the surface, Rsup
6 FLW = Surface Down-welling Long-Wave Radiation Total irradiance at the surface within the [4 – 100 m] interval:Spectral irradiance emitted downwards by the atmosphereFLW =Observed Downward Spectra Radiance – a clear sky dayWavelength (m)(adapated from Turner et al., 2004 in J. Atmos. Sci.
7 Surface Down-welling Long-Wave Radiation Remote SensingSatellite observations provide information on variables that controlDown-welling Longwave Fluxes at the surface:CloudsTemperature ProfilesHumidity profiles7
8 Surface Down-welling Long-Wave Radiation FLW as estimated in the LSA SAF from MSG/SEVIRIDown-welling Longwave Flux at the Surface (DSLF)SEVIRI/MSGSEVIRI/MSG Data:Channel 1 VIS0.6 mChannel 2 VIS0.8Channel 3 NIR1.6Channel 4 MIR3.9Channel 5 WV6.2Channel 6 WV7.3Channel 7 IR8.7Channel 8 IR/O39.7Channel 9 TIR10.8Channel 10 TIR12.0Channel 11 IR/CO213.4Channel 12HRVCloud identification:channels 1-4, 7, 9 & 10Other Information:atmosphere screen temperature (ECMWF forecast)total column water vapour(ECMWF forecast)
9 Surface Down-welling Long-Wave Radiation FLW as estimated in the LSA SAF from MSG/SEVIRIDown-welling Longwave Flux at the Surface (DSLF)Parameterization based on Stefan-Boltzman Law:Tcloudy-sky , cloudy-skyTclear-sky , clear-skyCloud cover fraction
10 Surface Down-welling Long-Wave Radiation FLW as estimated in the LSA SAF from MSG/SEVIRIDown-welling Longwave Flux at the Surface (DSLF)Fraction of CloudParameterization based on Stefan-Boltzman Law:Total column water vapour2m air temperature2m dew point depressionForecasts:(ECMWF)
11 Surface Down-welling Long-Wave Radiation 15 November 201100 UTC UTCCloud’s signature?
12 Surface Down-welling Long-Wave Radiation 15 November 201100 UTC UTCClear Sky -Cloudy/Partially Cloudy -
13 Surface Down-welling Long-Wave Radiation Generation Frequency - 30 minMSG projection & resolutionOver land ...Available sinceEurope – Feb 2005Full disk – Jul 2005But ... Algorithm changed in 2008!Also distributed with quality flag (pixel by pixel basis)
14 Surface Down-welling Long-Wave Radiation Daily Accumulated Long-wave FluxMSG projection & resolutionOver land ...Available sinceFull disk 2010Also distributed number of time-slots used for each (pixel) estimation.
15 Comparison with in situ measurements DSLF - ValidationComparison with in situ measurementsComparison with other satellite products (CERES onboard Aqua and Terra)Location of Ground Observations
16 clear sky cloudy DSLF - Validation Northern Europe Stations LSA SAF DSLF colocated in space and time withGround Stations & CERES (Northern Europe StationsJan Apr 2007 clear sky cloudyCERESSEVIRI DSLFBiasRMSEClear Sky-0.012.7-2.222.3All Sky-126.96.36.199.3Problems:Cloud identification at the edge of Meteosat diskDSLF model for ice cloudsTemperature inversions
17 Central Europe Stations DSLF - ValidationLSA SAF DSLF colocated in space and time withGround Stations & CERES (Central Europe StationsJan Apr 2007CERESSEVIRI DSLFBiasRMSEClear Sky-0.913.40.814.5All Sky-1.422.71.622.5Problems:Temperature inversions
18 Semi-arid & Desert Stations DSLF - ValidationLSA SAF DSLF colocated in space and time withGround Stations & CERES (Semi-arid & Desert StationsJan Apr 2007CERESSEVIRI DSLFBiasRMSEClear Sky13.026.8-4.414.1All Sky17.529.6-5.416.9Problems:Impact of high aerosol loads
19 DSLFLSA SAF estimates DSLF at the original satellite resolution (3 km at the sub-satellite point), every 30 –minutes, covering Meteosat diskSatellite data provide Cloud informationComparison with in situ data-10 Wm-2 < Bias < 10 Wm-2Root Mean Square Differences (RMS) ranges from considerably (from ~15 to 25 Wm-2)
20 DSLF Applications – Please see presentation in Session 8 As one of the components of the Surface Radiation Budget, DSLF applications include:Forcing of Land Surface (and Hydrology) modelsModel Assessment (surface and atmospherirc)Case Studies