Infrared Continental surface emissivity spectra retrieved from hyperspectral sensors. Application to AIRS observations Eric PEQUIGNOT

Transcription

1 Infrared Continental urface emiivity pectra retrieved from hyperpectral enor. Application to AIRS obervation Eric PEQUIGNO Laboratoire de Météorologie Dynamique LMD / IPSL eam «Atmopheric Radiation Analyi» Ecole Polytechnique Palaieau France

2 Infrared RE lambertian urface clear ky night Infrared RE lambertian urface clear ky night + + = ' ] 1 ] I Surface Emiion Upwelling Atmophere Emiion Reflected Downwelling Atmophere Emiion ' z z ' S = 1.1 Methodology

3 Multi-pectral method Multi-pectral method = ' ] ' ] ] I he formula hold only for window channel 1.2 Methodology In order to calculate one need: 1 identifying clear ky radiance MODIS cloud mak 2 knowing the thermodynamic tate of the atmophere H 2 O O 3 profile 3 etimating the urface kin temperature

4 2.1 Atmopheric thermodynamic tate Atmopheric tate: proximity recognition in Mean of the cloet atmopheric ituation in IGR hermodynamic Initial Gue Retrieval climatological dataet ee => p H 2 Op O 3 p Normalized Weight Function D = Selection of 11 input: -6 tropopheric ounding channel enitive to and H 2-5 difference of channel to contrain temperature and water vapor gradient X i X i ob IGR = 1 σ X i IGR 11 i 2 Approach validated on IGR dataet

5 Surface kin temperature: emi-tranparent ingle channel method Surface kin temperature: emi-tranparent ingle channel method 3.1 Etimation of the Surface Skin emperature = ' ] ' 1 ] at d d I Right hand ide determined from the cloet atmopheric ituation identified previouly. Calculation are performed uing 4A line-by-line code Emiivity variability of 324 AIRS channel calculated from oil water and vegetation emiivity pectra of MODIS/UCS and ASER/JPL librarie AIRS channel 528 at µm S >.5 and ~.96

6 3.2 Etimation of the Surface Skin emperature Comparion with MODIS kin June K AIRS June 23 MODIS June K 265 K 325 K Δ μ=-.46 K σ=1.81 K Value coherent with preently reported accuracie

7 Summary Summary = at ' ] ' ] ] I In order to calculate one need: 1 identifying clear ky radiance 2 knowing the thermodynamic tate of the atmophere H 2 O O 3 profile 3 etimating the urface kin temperature MODIS Cloud mak Proximity Recognition in IGR AIRS channel 528 at µm 4.1 Infrared emiivity pectrum

8 4.2 Infrared emiivity pectrum Infrared Emiivity Spectrum from 3.7 to 14 µm I 1 AIRS calculated if Péquignot et al. 26:.5 S and EAF + EAF ypically N AIRS ~ i interpolated at ref if AIRS cloe to ref ypically N ~ % II MODIS/UCS and ASER/JPL very high reolution emiivity pectra librairie 17 repreentative ample of oil and vegetation underampled at.5 µm from 3.7 to 14 µm ref = ] N ref = 27 point III Proximity recognition mean quare Sample with a ditance between D min and D max =1.4*D min are elected and their emiivity pectrum averaged.

9 5.1 Multi-pectral method reult Deert Savanna Emiivity Spectral variation 1 - Quartz rettrahlen band are well oberved and dominate the pectra - In quartz rettrahlen band increae with the % of vegetation. Red: AIRS multipectral method ±1σ lue: CIMSS/SSEC ±1σ lack: MODIS ±1σ µm Example of Savanna LMD : 25 to 4 ref AIRS CMISS : 6 ref MODIS µm

10 5.2 Multi-pectral method reult ropical foret Emiivity Spectral variation 2 Semi-Deert ropical foret emiivity cloe to 1 a expected For emi-deert area emiivity till influenced by quartz rettrahlen band Red: AIRS multipectral method ±1σ lue: CIMSS/SSEC ±1σ lack: MODIS ±1σ µm µm

11 5.3 Multi-pectral method reult Emiivity Regional Variation µm µm Sand Quartz µm µm

12 5.4 Multi-pectral method reult Emiivity Regional Variation µm µm Sand Quartz µm.4 1.

13 5.5 Multi-pectral method reult Deert Savanna Emiivity Seaonal variation 1 Sparely vegetated area emiivity repond to the rate of precipitation and the % of vegetation => High emiivity eaonal cycle amplitude For more detail ee Péquignot et al ubmitted Amplitude Amplitude Red: AIRS multipectral method lack: MODIS µm µm

14 5.6 Multi-pectral method reult ropical foret Emiivity Seaonal variation 2 Semi-Deert Amplitude Amplitude Red: AIRS multipectral method lack: MODIS µm µm

15 5.7 Multi-pectral method reult Impact of the emiivity eaonal cycle on AIRS Δ K µm

16 Concluion 1 Emiivity multi-pectral method work well and i adapted to intrument with high pectral reolution. 2 Difficulty to go further with comparion becaue we lack retrieved emiivity databae at very high pectral reolution. 3 Such emiivity pectra and urface kin temperature 3 year climatology of tropical zone 3 S-3 N hould help improving model of the earth urface-atmophere interaction and the retrieval of meteorological profile and cloud characteritic in particular emi tranparent cirru from infrared vertical ounder. 4 Eay to implement the Multi-Spectral Method in aimilation proce of data from hyperpectral enor AIRS/IASI. 5 With IASI pectral continuity we can probably kip the proximity recognition within MODIS/UCS and ASER/JPL emiivity librarie.