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Thermal Radiation Down-welling Long-wave Fluxes at the Surface

Thermal Radiation Down-welling Long-wave Fluxes at the Surface. Isabel F. Trigo. MSG-based Radiation Products Down-welling Long-wave Flux (DSLF) Definition Algorithm Basis The LSA SAF DSLF product from MSG Validation. Solar Radiation. Thermal Radiation. 30%. 23%. 90%. 4%. 47%.

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Thermal Radiation Down-welling Long-wave Fluxes at the Surface

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  1. Thermal Radiation Down-welling Long-wave Fluxes at the Surface Isabel F. Trigo

  2. MSG-based Radiation Products Down-welling Long-wave Flux (DSLF) • Definition • Algorithm Basis • The LSA SAF DSLF product from MSG • Validation

  3. Solar Radiation Thermal Radiation 30% 23% 90% 4% 47% Radiation Budget Earth Surface • Short-Wave Net Radiation • Loss • Gain ? • Long-Wave Net Radiation • Loss • Gain ? Adapted from K. Trenberth, J. Fasullo, and J. Kiehl.

  4. Solar Radiation Thermal Radiation 30% 23% 23% 4% 90% 7% Radiation Budget Earth Surface • Short-Wave Net Radiation • Loss • Gain X • Long-Wave Net Radiation • Loss • Gain X Adapted from K. Trenberth, J. Fasullo, and J. Kiehl.

  5. Surface Down-welling Long-Wave Radiation Down-welling Long-wave Fluxes at the Surface Long-wave Radiation reaching the Surface: • Essentially emitted by the lowest 100 m of the atmosphere Emitted by the atmosphere, Ra • It is controlled by • concentration of abosrbing gases • CO2, CH4, H2O, ... • presence of clouds, clouds phase • temperature profile & temperature of cloud base .... Reflected by the surface, Rrefl Emitted by the surface, Rsup

  6. Surface Down-welling Long-Wave Radiation Total irradiance at the surface within the [4 – 100 m]interval: Spectral irradiance emitted downwards by the atmosphere FLW = Observed Downward Spectra Radiance – a clear sky day 20 15 12.5 10.5 9 8 7 Wavelength (m) (adapated from Turner et al., 2004 in J. Atmos. Sci.

  7. Surface Down-welling Long-Wave Radiation Remote Sensing • Satellite observationsprovide information on variables that control • Down-welling Longwave Fluxes at the surface: • Clouds • Temperature Profiles • Humidity profiles 7

  8. Surface Down-welling Long-Wave Radiation FLW as estimated in theLSA SAF from MSG/SEVIRI Down-welling Longwave Fluxat the Surface (DSLF) SEVIRI/MSG Data: SEVIRI/MSG Cloud identification: channels 1-4, 7, 9 & 10 • Other Information: • atmosphere screen temperature (ECMWF forecast) • total column water vapour (ECMWF forecast)

  9. Surface Down-welling Long-Wave Radiation FLW as estimated in theLSA SAF from MSG/SEVIRI Down-welling Longwave Fluxat the Surface (DSLF) Parameterization based on Stefan-Boltzman Law: Tcloudy-sky , cloudy-sky Cloudcover fraction Tclear-sky , clear-sky

  10. 2m air temperature Total column water vapour 2m dew point depression Surface Down-welling Long-Wave Radiation FLW as estimated in theLSA SAF from MSG/SEVIRI Down-welling Longwave Fluxat the Surface (DSLF) Fraction of Cloud Parameterization based on Stefan-Boltzman Law: Forecasts: (ECMWF)

  11. Surface Down-welling Long-Wave Radiation 15 November 2011 00 UTC 12 UTC Cloud’s signature?

  12. Surface Down-welling Long-Wave Radiation 15 November 2011 00 UTC 12 UTC Clear Sky - Cloudy/Partially Cloudy -

  13. Surface Down-welling Long-Wave Radiation • Generation Frequency - 30 min • MSG projection & resolution • Over land ... • Available since • Europe – Feb 2005 • Full disk – Jul 2005 But ... Algorithm changed in 2008! Also distributed with quality flag (pixel by pixel basis)

  14. Surface Down-welling Long-Wave Radiation Daily Accumulated Long-wave Flux • MSG projection & resolution • Over land ... • Available since • Full disk 2010 Also distributed number of time-slots used for each (pixel) estimation.

  15. DSLF - Validation • Comparison with in situ measurements • Comparison with other satellite products (CERES onboard Aqua and Terra) Location of Ground Observations

  16. clear sky cloudy DSLF - Validation LSA SAF DSLFcolocated in space and time with Ground Stations & CERES (http://aqua.nasa.gov/about/instrument_ceres.php) Northern Europe Stations Jan 2006 - Apr 2007 • Problems: • Cloud identification at the edge of Meteosat disk • DSLF model for ice clouds • Temperature inversions

  17. DSLF - Validation LSA SAF DSLFcolocated in space and time with Ground Stations & CERES (http://aqua.nasa.gov/about/instrument_ceres.php) Central Europe Stations Jan 2006 - Apr 2007 • Problems: • Temperature inversions

  18. DSLF - Validation LSA SAF DSLFcolocated in space and time with Ground Stations & CERES (http://aqua.nasa.gov/about/instrument_ceres.php) Semi-arid & Desert Stations Jan 2006 - Apr 2007 • Problems: • Impact of high aerosol loads

  19. DSLF • LSA SAF estimates DSLF at the original satellite resolution (3 km at the sub-satellite point), every 30 –minutes, covering Meteosat disk • Satellite data provide Cloud information • Comparison with in situ data • -10 Wm-2 < Bias < 10 Wm-2 • Root Mean Square Differences (RMS) ranges from considerably (from ~15 to 25 Wm-2)

  20. DSLF 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) models • Model Assessment (surface and atmospherirc) • Case Studies

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