AIRS Land Surface Temperature and Emissivity Validation Bob Knuteson Hank Revercomb, Dave Tobin, Steve Ackerman University of Wisconsin-Madison Space Science and Engineering Center Robert.Knuteson@ssec.wisc.edu AIRS Science Team Meeting, Pasadena, CA March 2006 1
Project Description • Land Surface Characterization Using High Spectral Resolution AIRS and Moderate Spatial Resolution MODIS Observations from the EOS Aqua Platform • R. Knuteson - PI • NASA Aqua Validation • Funded by NASA Terrestrial Ecosystems • Three year grant (one year remaining) • Themes: (1) Improve the use of sounder data over land. (2) Assess land surface changes in regions sensitive to climate variations, e.g. semi-arid. 2
Topics • AIRS Temperature Validation - ground truth sites (ARM SGP) - MODIS inter-comparison • AIRS IR Emissivity Validation - ARM SGP Matchup project (joint). - Selected granule files for case studies. - Daily “clear” analysis. - Collaboration with JCSDA activities. 3
AIRS Temperature Validation: Ground Truth ARM SGP Site • Mid-Continental (Oklahoma) • Provides surface and atmospheric profiling measurement accuracy • Long-term continuous observations are ideal for comprehensive satellite validation 4
AIRS Temperature Validation: Ground Truth Dec 2005 Oklahoma 295 Comments Nighttime Hourly Overpass variability ∼ 8:45 UT is ∼ 1 K Day-Day variability is ∼ 5 K Day/Night Daytime variability Overpass is ∼ 15 K ∼ 19:45 UT 270 5
AIRS Temperature Validation: Ground Truth July 2005 Oklahoma 320 Comments Nighttime Hourly Overpass variability ∼ 8:45 UT is ∼ 5 K (day) Day-Day variability is ∼ 5 K Daytime Day/Night Overpass variability ∼ 19:45 UT is ∼ 15 K 285 6
Infrared Radiative Transfer Equation (lambertian surface) � tot tot N B ( T ( P )) d e B ( T ) ( 1 e ) N � = � � + � � + � � � � � � S � � � � � � � � atm Surface Surface N � � Emission Reflection Skin Temperature & Surface Emissivity 7
AIRS Temperature Validation: Ground Truth Comments SGP Site Emissivity 12 µ m has a maximum 9 µ m in a narrow Vegetation region at 60%-40% 12 µ m: combination (830 cm -1 -832 cm -1 ) Bare Soil 8
AIRS Temperature Validation: Ground Truth Comments Using an AIRS validation database developed with Dave Tobin using ARM measure- ments. 9
AIRS Temperature Validation: Ground Truth Comments AIRS B.T. minus 2004 ARM SGP ARM IRT 12 µ m: -1.0 ± 1.0 K 9 µ m: PRELIMINARY -3.4 ± 0.8 K NIGHT-TIME 4 µ m: CLEAR SKY -2.2 ± 0.8 K 10
Topics • AIRS Temperature Validation - ground truth sites - AIRS/MODIS inter-comparison (Monthly Composite Level 3 Products) • AIRS IR Emissivity Validation - ARM SGP Matchup project (joint). - Selected granule files for case studies. - Daily “clear” analysis. - Collaboration with JCSDA activities. 11
AIRS Temperature Validation: MODIS Comparison Comments 320 Day/Night algorithm 300 5 km spatial resolution MOD11C 270 product JULY 2003 MODIS (MOD11C) – DAY-TIME 12
AIRS Temperature Validation: MODIS Comparison Comments 320 MODIS Good Data Flag Used. 300 Reduced from 0.05 degree to 1 degree resolution 270 Within Std Dev. < 1 K JULY 2003 MODIS Averaged to 1 degree Grid 13
AIRS Temperature Validation: MODIS Comparison MODIS (v. 4) AIRS (v. 4) Comments AIRS minus MODIS July 2003 AIRS - MODIS Mean: +1.4 K Std Dev: 2.1 K -5 0 5 -6 0 6 14
AIRS Temperature Validation: MODIS Comparison 320 Comments North K American Day-Time 250 Mean Tsurface Bias AIRS minus MODIS within +2 ± 1 K except -2 during Winter 1 12 MONTH of 2003 15
AIRS Temperature Validation: MODIS Comparison 6 Comments 0 Indication JANUARY of a Winter -6 Polar Surface 2003 AIRS minus MODIS Temp. Bias in the 6 AIRS gridded L3 0 product JULY -6 16
Topics • AIRS Temperature Validation - ground truth sites - MODIS inter-comparison • AIRS IR Emissivity Validation - ARM SGP Matchup project (with Tobin). - Selected granule files for case studies. - Daily “clear” analysis. - Collaboration with JCSDA activities. 17
AIRS IR Emissivity Validation: ARM SGP Matchup 1.0 Comments 9 µ m GRASS AIRS FOV 12 µ m contains weighting 4 µ m E of Pasture or Wheat (Grass) and Exposed Bare Soil BARE SOIL (Silicates) 0.75 500 3000 18 Wavenumber (cm -1 )
AIRS IR Emissivity Validation: ARM SGP Matchup 1.0 Comments Seasonal variation due to exposure 0.9 of soil after 1.0 WHEAT harvest. 9 µ m: 2-3 % 4 µ m: 0.9 4-6 % 19
AIRS IR Emissivity Validation: ARM SGP Matchup Comments A 50% vegetation 10 W/m 2 fraction at Ts = 300K implies an anthropogenic affect of about 5 W/m 2 Upwelling Flux with a Estimate at ARM SGP seasonal variation of 2 to 3 W/m 2 . 20
Topics • AIRS Temperature Validation - ground truth sites - MODIS inter-comparison • AIRS IR Emissivity Validation - ARM SGP Matchup project (joint). - Selected granule files for case studies. - Daily “clear” analysis. - Collaboration with JCSDA activities. 21
AIRS IR Emissivity Validation: Case Studies 1.0 Thessaly Plain, Greece Emissivity Relative Libyan Desert Satellite Validation 0.7 Target Site (27.12N,26.10E) 16 November 2002 00:00-00:06 UTC (15-km FOV) 22
AIRS IR Emissivity Validation: Daily “Clear” File Analysis • AIRS Temperature Validation - ground truth sites - MODIS inter-comparison • AIRS IR Emissivity Validation - ARM SGP Matchup project (joint). - Selected granule files for case studies. - Daily “clear” analysis. - Collaboration with JCSDA activities. 23
AIRS IR Emissivity Validation: Clear Match 16 NOV 2002 Comments Clear Ocean (Blue) Clear Land (Red) Using Aumann Clear Tests 24
AIRS IR Emissivity Validation: In Collaboration with the JCSDA (LeMarshal) • Polar (|latitude| > 75 degrees) - Arctic, Antarctic • Snow covered land (|lat| > 45 degrees) - Sibera, Alaska, Canada, Scandanavia • Deserts - Saraha, China, Australia • Semi-Arid Regions - Sahel, Western U.S.. 25
Progress Summary • Continental ARM SGP site is being used for Temperature and IR Emissivity validation. • Global AIRS L3 are compared with MODIS L3 products for monthly composites. • Case Studies are being used to assess L2 products on a granule basis (Working Group). • AIRS “clear” daily data stream will be used to create a global single field of view emissivity database for use by the AIRS ST and JCSDA. 26
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