Infrared continental surface emissivity spectra retrieved from IASI observations

Transcription

1 Infrared continental urface emiivity pectra retrieved from IASI obervation E. Péquignot a A. Chédin b N. A. Scott b a CNES - Centre Spatial de ouloue ouloue France b Laboratoire de Météorologie Dynamique IPSL Ecole Polytechnique Palaieau France. ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 1

2 Spectral variation of emiivity in IR from MODIS/UCS and ASER/JPL emiivity librarie are oil: quartz µm Quartz Rettrahlen band are oil: calcite Snow and Ice Vegetation are oil: gypum Spectral variation impact on IR emiivity: up to 5% particularly over bare oil in quartz Rettrahlen band ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 2

3 1. Angular variation of emiivity in IR 1. /.5 7 for <4. µm 14 Labed J. and M.P. Stoll 1991 International Journal of Remote Sening Angular variation impact on IR emiivity: effect< 5% For IR ounder at 1km patial reolution thi effect i even maller patial averaging.75 9 Concluion : For IR ounder emiivity angular variation i a 2 nd order effect in comparion to pectral variation for viewing angle lower than 4. => Lambertian aumption ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 3

4 ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 4 Infrared RE lambertian urface clear ky night Surface Emiion Upwelling Atmophere Emiion ' z z ' S = + + = ' 1 I ε ε Reflected Downwelling Atmophere Emiion for a Lambertian urface

5 ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 5 Multi Spectral Method MSM = ' ' I ε In order to calculate one need: 1 identifying clear ky radiance -> EUMESA IASI L2 cloud mak baed on AVHRR 2 knowing the thermodynamic tate of the atmophere H 2 O O 3 profile -> EUMESA IASI L2 product 3 etimating the urface kin temperature he formula hold only for window channel Péquignot et al. 28 Infrared continental urface emiivity pectra retrieved from hyperpectral enor. Application to AIRS. JAMC.

6 ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 6 Surface kin temperature : emi-tranparent pectral band µm = ' ' ε ε at d d I right hand ide calculated from EUMESA L2 atmopheric profile uing a Fat Radiative ranfer Model baed on 4A line-by-line code 4A : Scott and Chédin 1981 Emiivity variability of the 8461 IASI channel calculated from oil and vegetation emiivity pectra of MODIS/UCS and ASER/JPL librarie Spectral band µm =12.17 µm S >.5 and ~.97

7 ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 7 Infrared Emiivity Spectrum from 3.7 to 14 µm = ' ' I ε calculated for about 9 IASI channel elected for there high enitivity to urface parameter MSM Emiivity databae : pectra for variou oil and vegetation type extracted from MODIS/UCS and ASER/JPL emiivity librarie. - ampling : µm at.5 µm reolution. Leat quare minimization + hape adjutment Emiivity continuou pectrum between 3.7 and 14. µm

8 Reult for Jan 28 1 t 9 th 25 th : pectral variation 1 Deert Savanna MSM CIMSS-SSEC EUMESA MSM CIMSS-SSEC EUMESA µm µm - Quartz rettrahlen band are well oberved and dominate the pectra - In quartz rettrahlen band increae with the % of vegetation Example of Savanna ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 8

9 Reult for Jan 28 1 t 9 th 25 th : pectral variation 2 ropical foret Semi-Deert µm µm - ropical foret emiivity cloe to 1 a expected - For emi-deert area emiivity till influenced by quartz rettrahlen band ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 9

10 Reult for Jan 28 1 t 9 th 25 th : urface temperature over land Difference between urf calculated by MSM and urf provided by L2 - Eumetat = -.9 K = 1 K Value coherent with preently reported accuracie ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 1

11 Expected accuracy on emiivity calculated by the MSM Statitic done on 1 imulated cae : For each imulation we have randomly choen : 1/ an emiivity pectrum MSM emiivity databae 2/ an atmopheric ituation IGR dataet 3/ a urface temperature defined a lowet_level_igr + Gauianµ=K=4K MSM - heoretical accuracy on : < 1.5% Other effect ha to be conidered for operational proceing : - Reidual cloud - Potential wavelength dependant bia between radiative tranfer imulation and obervation - Angular variation of Expected effect from AIRS experience : error increae of about 25-5 % Péquignot et al 28 ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 11

12 Comparion with CIMSS and EUMESA L2 Deert Savanna - Good agreement between MSM CIMSS and EUMESA emiivitie except at 4 µm ignal lower in that pectral region emiivity harder to etimate - Lower patial diperion for CMISS and MSM emiivity ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 12

13 Comparion with CIMSS and EUMESA L2 ropical foret Semi-Deert ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 13

14 Concluion 1 Emiivity Multi-Spectral Method MSM work well and i adapted to intrument with high pectral reolution. 2 We need to analyze more data to go further with comparion and build a climatology of emiivity retrieved from IASI 3 Such emiivity pectra and urface kin temperature hould help improving model of the earth urface-atmophere interaction and the retrieval of meteorological profile from infrared vertical ounder. 4 Eay to implement the Multi-Spectral Method in Near Real ime inverion data proceing. ISC XVI : Angra do Rei - rail May 28 E. Péquignot DC/SI/MO 14