LST and EM retrievals from SEVIRI onboard Meteosat: Algorithms, uncertainties, and validation

Transcrição

1 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LST and EM retrievals from SEVIRI onboard Meteosat: Algorithms, uncertainties, and validation Sandra C. Freitas, Isabel F. Trigo, José Bioucas Dias, Frank Göttsche, Folke Olesen

2 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: Outline T he La nds A F La nd S urfa c e E m is s ivity A lg orithm & E rrors La nd S urfa c e Tem perature A lg orithm & E rrors In-s itu Va lidation LS T & LS E P roduc t C ha ra c teris tic s

3 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LandSAF AIM Develop techniques that allow an effective use of MSG and EPS data related to: LAND LAND-ATMOSPHERE Interactions BIOSPHERIC Applications Provide Products + User Support FMI

4 LandSAF - Products Surface Radiation Budget LST Albedo LongWave Flux ShortWave Flux Vegetation Fraction Veg Cover LAI FAPAR Surface Water Balance Snow Cover Evapotranspiration Wild Fires Fire Detection Fire Radiative Power Fire Risk (Europe) SEVIRI/Meteosat AVHRR, ASCAT/MetOp Ministério da Ciência, Tecnologia e Ensino Superior Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL:

5 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LandSAF Chronogram Meteosat-8 (MSG-1) MetOp-A Meteosat-9 (MSG-) MetOp-B Meteosat-10 (MSG-3) MetOp-C Meteosat-11 (MSG-4) MTG Initial Operations Phase Feb 005 Continuous Development & Operations Phase Mar 007

6 LSE Algorithm Vegetation Cover Method [Caselles et al.] Effective LSE ε eff = ε + ε veg FVC bg ( 1 FVC) Fraction of Vegetation Cover Each IR channel / Broad Band Each Land-Cover Classes (IGBP classification) Using spectral library values + SEVIRI response functions Associated Uncertainties dε eff = 4 dε FVC(1 FVC) Simplification of equation Excess emissivity due to multiple internal reflections Trigo, I. F. et al. (008) in IEEE Trans. Geosci. Remote Sens., 46. Ministério da Ciência, Tecnologia e Ensino Superior Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL:

7 Error Bars eff LSE Algorithm [( ) (( ) ) (( ) ) ] 1 FVCδε + FVC δε + ε ε δfvc dε δε = + veg 1 bg veg bg eff Vegetation / baresoil variability within each Land-Cover class FVC Uncertainty Emissivity [.] FVC=0 FVC=0.7 Trigo, I. F. et al. (008) in IEEE Trans. Geosci. Remote Sens., 46. Ministério da Ciência, Tecnologia e Ensino Superior Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL:

8 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: SEVIRI channels & LST Split-Window Channels Desert Areas Evergreen Forest Solar Contamination High variability of EM Wavelength [µm]

9 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LST - Algorithm Generalised Split-Window 10.8µ m and 1.0µ m Trained using CLEAR SKY synthetic SEVIRI/MSG data 1 ε ε T T1.0 1 ε ε T10.8 T1. 0 LST = ( A1 + A + A3 ) + ( B1 + B + B3 ) + C ε ε ε ε GSW parameters depend on: 1. total column water vapour. viewing angle ECMWF fc LST depends explicitly on LSE IR10.8 & IR1.0: ε = 1 ( LSE _ IR LSE _ IR1.0 ) ε = LSE _ IR10.8 LSE _ IR1.0

10 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: Generalised Split-Window LST_Errors (K) LST Algorithm Uncertainty Verified against independent dataset ( ~ profiles). Algorithm uncertainty increases with view angle & water vapour, i.e., with optical path. ~ NADIR Zenith Ang ~ 40º Zenith Ang ~ 75º (cm) (cm) (cm) TCWV Assuming well known inputs without errors 4 0 -

11 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LST Error Propagation Errors Bars S LST f = X + i i X σ i j f θ j σ θ j + LST Explicit input variables Sensor noise & Emissivity Algorithm uncertainty Retrieval conditions Implicit input variables TCWV (uncertainty on ECMWF fc) & View angle

12 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LST Error Propagation Errors Bars S LST f = X + i i X σ i j f θ j σ θ j + LST EMISSIVITY SENSOR NOISE WATER VAPOUR DRY LST Error (K) LST Error (K) LST Error (K) MOIST

13 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: SEVIRI LST vs In-situ data Validation Site - Homogeneous & dry region Gobabeb Namibia - large gravel plains In-situ LST ( C) In-situ LST ( C) Sep 008 Nov 008 RMSE = 1.1 C ErrorBar =.9 RMSE = 1.4 o ErrorBar =.7 C SEVIRI LST ( C) o o C o C Jan 009 Mar 009 RMSE =.1 C ErrorBar =.5 RMSE = 1.7 ErrorBar = SEVIRI LST ( C) o o C o o C C Main source of errors: uncertainty on bare ground Emissivity RMSE < Monthly Average of ErrorBar Higher Discrepancies SEVIRI LST << In-situ LST Clouds Contamination or Shadows

14 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: LST - Product Characteristics LST LST Error Bars Good coverage View Angle Water Vapour Dry regions & uncertainty on EM Maskout (SLST > 4K) Moist regions &/or View Angle

15 LST - Product Characteristics LST LST Error Bars Dissemination via Eumetcast and Web Generation Frequency - 15 min clear sky pixels... over land... Available since Europe Feb 005 Full disk Jul Ministério da Ciência, Tecnologia e Ensino Superior Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL:

16 LSE Product Characteristics EM 3.9µm Dissemination upon request Generation Frequency daily LSE & Error Bars over land... Available since Jan 008 EM 8.7µm EM 10.8µm EM 3 14µm EM 1.0µm Ministério da Ciência, Tecnologia e Ensino Superior Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL:

17 Instituto de Meteorologia, I. P. Rua C Aeroporto de Lisboa Lisboa Portugal Tel.: (351) Fax: (351) informacoes@meteo.pt URL: