Infrared continental surface emissivity spectra and skin temperature retrieved

Transcription

1 Infrared continental urface emiivity pectra and kin temperature retrieved from IASI obervation Capelle V., Chédin A., Péquignot E., N. A Scott Schlüel P., Newman S. ITSC 18 March 2012 Touloue, France

2 Why Focuing on T and ε? Introduction To improve the determination of the tropopheric propertie: Thermodynamic propertie (T, H2O, etc ) aerool Trace gae concentration Eential to etimate the radiative budget Neceary to have an accurate pectral etimation of emiivity (emiivity often conidered a contant). Advantage of uing 2nd generation infrared ounder (AIRS, IASI)? Can provide emiivity pectra at high reolution Global view and long-term monitoring of continental urface (e.g: Sahel evolution) Sand/Bare oil Vegetation from MODIS/UCSB and ASTER/JPL emiivity librarie Snow/Ice

3 Infrared RTE (lambertian urface, clear ky, night) z lnp TOA urf I(, ( (, B(, T z 1 (, ) B[, T] d (, (1 ( ) (, (, 1 (, ) B[, T] Surface Emiion '(, Upwelling Atmophere Emiion z 0 ' (, ) (, ) S (, ) ' (, d Reflected Downwelling Atmophere Emiion for a Lambertian urface

4 Multi Spectral Method (MSM) Satellite ob : IASI P ol, view. angle TIGR tranmittance cloud mak TB ob TB calc Péquignot et al, JAMC, 2008 Capelle et al, JAMC, 2012 Atmophere characterization (T, H2O, O3 profile) : => proximity recognition within the TIGR dataet T determination RTE olved for 3 channel with ε independent of the urface type The three channel are located at ~12µm, ε ~0.97 ε determination => RTE olved for 101 hindge point

5 Determination of the continuou emiivity pectrum ε calculated for 101 hinge point Dicontinuou pectrum with a demontrated accuracy of le than 1.5% at 12 µm and ~4.5% at 4 µm. MSM emiivity databae: 165 high pectral reolution emiivity laboratory meaurement of different ample of typical Earth urface are elected from MODIS/UCSB and ASTER/JPL emiivity librarie. They are linearly interpolated at 0.05 µm reolution between 3.7 and 14.0 µm. Proximity recognition + hape fit procedure Emiivity continuou pectrum at 0.05 µm reolution between 3.7 and 14.0 µm

6 Reult for urface temperature: Comparion with MODIS and the ECMWF forecat data IASI MODIS June 2008 December 2008 Good agreement with MODIS urface temperature (td - dev of about 1.4 K) and ECMWF fct (bia < 0.5K). ECMWF-FC IASI/MSM reult are in between MODIS and ECMWF fct With ECMWF, mall biae but with a large tandard deviation in December (??) June 2008 Dec ± 1.5K 1.19 ± 1.4K MODIS IASI N. Hem ± 1.5K S. Hem ± 1.1K N. Hem ± 1.3K S. Hem ± 1.3K ECMWF FC IASI 0.45 ± 1.7 K 0.24 ± 2.4K With MODIS, biae depend on the eaon: (-0.8K in winter and ~-1.9K in ummer, with a td dev larger in ummer) => A part of thi difference can be explained by the diurnal cycle impact due to the 1 hour time hift between IASI and TERRA (21h30.v. 22h30) -> ee Capelle et al., 2012

7 Reult for the infrared urface emiivity pectrum: comparion with MODIS Local maximum at 8.65µm Deert Sahel The accurate hape of the pectrum characterize the oberved urface (high reolution in the quartz rettrahlen 8 µm band i important) In general, good agreement with MODIS low reolution emiivitie Tropical foret The IASI/MSM method actually reproduce the local maximum of emiivity at 8.65 µm oberved in the high pectral reolution laboratory pectra for and oil.

8 Time erie from July 2007 to December2011 Example of the rettrahlen band at 3.8 and 8.55 µm Deert 3.8µm 8.55µm NDVI Sahel GPCP SOILM Savanna Tropical foret Variation (eaonal) trongly depend on the urface type: no variation over deert or tropical foret, trong variation over Sahel or Savanna. The variation follow the NDVI / oil moiture / precip : emiivity increae with vegetation and/or the oil water content Opportunity of long-term monitoring of continental urface (Metop1, 2, 3, etc ) at global cale.

9 Application of the IASI MSM at local cale: Comparion with ARIES emiivity from the MEVEX Oman campaign, May 2009 Emiivity meaurement during the aircraft MEVEX campaign of the MetOffice: IR radiance collected by ARIES interferometer on-board the FAAM BAe Atmopheric Reearch Aircraft During low-level flight, the urface emiivity can be derived directly from the hyperpectral data. => Two flight at low-level were elected a uitable for emiivity retrieval from ARIES and compared here with IASI-MSM emiivity for each pot IASI-MSM ARIES Emiivity at 9 micron: Flight track km

10 Application of the IASI MSM at local cale: 23 Comparion with ARIES emiivity from the MEVEX Oman campaign, May 2009 IASI-MSM ARIES In general, good agreement IASI-MSM(local) with ARIES Large patial variation of emiivity at very local cale conitent between ARIES and IASI-MSM. Ex: 10% variation for an area < 0.5 At 12µm, difference < 0.02, but IASI-MSM alway greater than ARIES. MODIS in-between. At 8 µm, in general, difference < Larget difference might be due to our 0.25 box averaging given the large variation of emiivity at thi wavelength.

11 Concluion Final product: High pectral reolution continental urface emiivity pectra (0.05 µm from 3.7 to 14 µm), and urface temperature from July 2007 up to now. Reult at global cale : Comparion of T with MODIS and ECMWF fct and of emiivity with MODIS have been performed with good reult. The reulting emiivity pectra well reproduce mall variation, uch a the local maximum at 8.65 μm oberved in the laboratory pectra from the 165-MOD-AST emiivity librarie for and oil. Reult at local cale (=iai pot): Good agreement with in-itu meaurement from ARIES IASI-MSM emiivity reproduce the large variation een by ARIES over quite mall area.

12 Perpective Improvement of the tudie at local cale: Why IASI-MSM emiivity i in general greater (<0.02) than the ARIES one? Monitoring of continental urface (vegetation cover, drought..): Uing the trong correlation between oil propertie (vegetation, moiture) and emiivity to follow the evolution of the urface propertie Retrieving aerool propertie above continent and particularly above deert till difficult to achieve at olar wavelength require knowledge of the urface propertie uch a T and ε Aerool retrieval over ea retrieved from IASI Aerool mak (July 2008) Peyridieu et al., in prep. Pernin et al., priv. comm"