The AIRS Forward Model: Validation & In-Orbit RTA L. Larrabee - PowerPoint PPT Presentation

September 2002 AIRS Science Team Meeting The AIRS Forward Model: Validation & In-Orbit RTA L. Larrabee Strow Scott E. Hannon Howard E. Motteler Sergio De Souza-Machado Rodrigo Ferreira de Souza (INPE) Lisa LeBlanc L A N Y D R A B A M L T F Department of Physics U M B C I O M O Y R T E I S University of Maryland Baltimore County (UMBC) R C E O V U I N N U T Y Baltimore, MD 21250 1 6 9 6 L. Strow, UMBC 1

September 2002 AIRS Science Team Meeting Overview • Validation data: ECMWF, PREPQC, ARM-CART • AIRS observations: July 20, Aug 31, Sept. 1,2,5,6,9,10,11 • Aug/Sept. data validation done with the new AIRS-RTA at the post-defrost frequencies • Changes to AIRS-RTA from pre-launch version include: (1) correct frequencies, (2) fringes, (3) new water continuum, and (4) improved CO 2 at 4.3 microns • Plan to deliver new AIRS-RTA after final testing next week. Includes 2 new predictors for the water continuum, needed because we added temperature dependence to the foreign continuum. • This new AIRS-RTA contains no direct corrections from AIRS validation. • Will cover clear FOV selection, bias observations, differences between AIRS-RTA and those based on GENLN2, and some very initial observations of non-LTE and cirrus. L. Strow, UMBC 2

September 2002 AIRS Science Team Meeting Clear Selection: 1st find uniform golfballs Our FOV selection was based on three semi-independent tests: (1) the uniformity of the FOV radiances compared to all adjacent FOVs, (2) window channels at different wavelengths must have the same B(T), after correction for water, and (3) remove outliers by forcing agreement between observed and computed SST to ± 4K. Uniform B(T) test: • test channels = [ 759, 903, 2328, 2333 ] = [900, 961, 2611, 2616 cm − 1 ] • calculate BT mean of test channels for every FOV • calculate | ∆ BT | for all 8 adjacent FOVs • FOV is uniform only if max | ∆ BT | < ∆ BT max • ∆ BT max = 0.25 Kelvin L. Strow, UMBC 3

September 2002 AIRS Science Team Meeting Clear Test The clear test compares estimated surface temperatures for some subset of channels. Observed window channel radiances are converted to surface temperatures by adjusting them for the estimated atmospheric effects using the ECMWF model profile. The test channels are distributed into bins to allow channel (ie bin) averaging prior to comparing the temperatures. The bin temperature comparisons can either between two bins or between a bin and the model surface temperature. L. Strow, UMBC 4

September 2002 AIRS Science Team Meeting Clear Test Procedures • use the nearest ECMWF profile and sea surface emissivity • derive an effective sea surface temperature for the test channels by subtracting out the atmospheric effects. This also requires a sea surface emissivity model. • skip if T eff < 273 K since it is ice not open sea • sort individual channel surface temperatures into averaging bins • ignore shortwave test channels if daytime • compute bin average surface temperature • compare temperatures between bins • if delta BT is larger than max allowed difference, profile fails • ∆ BT < 4 Kelvin for comparisons with ECMWF model T sea • ∆ BT < 0 . 4 Kelvin for comparisons between bins • max land fraction = 0.001 L. Strow, UMBC 5

September 2002 AIRS Science Team Meeting bin id1 id2 id3 id4 id5 id6 id7 1 555 559 562 2 757 758 760 764 766 769 3 843 847 848 853 857 858 Channel Bins 4 892 893 896 897 902 903 5 1291 1292 1293 1297 1298 6 2213 2214 2215 2216 2217 2218 2219 7 2327 2328 2331 2334 2346 2361 8 2388 bin1 bin2 ∆ T 1 2 0.4 2 3 0.4 3 4 0.4 Bin comparisons 4 5 0.4 4 0 4 4 7 0.4 6 7 0.4 8 0 4 L. Strow, UMBC 6

September 2002 AIRS Science Team Meeting Clear Test Channels 290 280 270 260 B(T) in K 250 240 230 220 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 7

September 2002 AIRS Science Team Meeting 2002.07.20 AIRS Visible False Colour Granule029 120 100 80 60 40 20 10 20 30 40 50 60 70 80 90 L. Strow, UMBC 8

September 2002 AIRS Science Team Meeting Forward Model Sensitivity to SRF Parameters 300 B(T) in K 250 a. 0.4 0.2 1% centroid error 0 −0.2 b. <−−−− Error in K −−−−> −0.4 0.4 0.2 2% width error 0 −0.2 c. −0.4 0.4 0.2 fringe error 0 −0.2 d. −0.4 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 9

September 2002 AIRS Science Team Meeting Bias Calculations • ECMWF used for global bias calculations. • Bias calculations only over water, generally night only • Restrict latitude to ± 60 degrees • All scan angles included, generally nadir is 2-3X more likely to be clear than 45 degrees • Raob and ARM-CART site results extremely preliminary L. Strow, UMBC 10

September 2002 AIRS Science Team Meeting Sept. 10 Bias and Std 280 B(T) in K 260 240 220 2 1 O−C in K 0 −1 2 Std in K 1.5 1 0.5 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 11

September 2002 AIRS Science Team Meeting Fringe Effects, Aug 18, Post-Defrost 2 1 Bias in K 0 w/o fringes −1 w/ fringes −2 0.4 0.2 ∆ B(T) in K 0 −0.2 −0.4 Effect of fringes −0.6 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 12

September 2002 AIRS Science Team Meeting Fringe Effects, Aug 18, Post-Defrost, Zoom w/o fringes 1 w/ fringes 0.5 Bias in K 0 −0.5 −1 0.5 Effect of fringes ∆ B(T) in K 0 −0.5 1250 1260 1270 1280 1290 1300 1310 1320 1330 Wavenumber (cm −1 ) L. Strow, UMBC 13

September 2002 AIRS Science Team Meeting Fringe Effects, Aug 18, Post-Defrost, Zoom 1.5 w/o fringes w/ fringes 1 Bias in K 0.5 0 −0.5 0.5 Effect of fringes ∆ B(T) in K 0 −0.5 2190 2200 2210 2220 2230 2240 2250 Wavenumber (cm −1 ) L. Strow, UMBC 14

September 2002 AIRS Science Team Meeting Bias Stability: Sept 10 vs Aug 31 Global Bias (Sept 10 − Aug 31) ECMWF Derived Bias 280 B(T) in K 260 240 220 0.4 0.2 ∆ Bias 0 −0.2 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 15

September 2002 AIRS Science Team Meeting Mean and Std of Daily Global Bias over 7 days in Sept. 280 B(T) in K 260 240 220 2 O − C in K 1 0 −1 0.3 Std in K 0.2 0.1 0 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 L. Strow, UMBC 16

September 2002 AIRS Science Team Meeting Mean and Std of Daily Global Bias over 7 days in Sept. 250 240 B(T) in K 230 220 1.5 O − C in K 1 0.5 0 0.2 Std in K 0.1 0 650 655 660 665 670 675 680 L. Strow, UMBC 17

September 2002 AIRS Science Team Meeting Mean and Std of Daily Global Bias over 7 days in Sept. 280 B(T) in K 260 240 220 1 O − C in K 0.5 0 −0.5 0.2 Std in K 0.1 0 690 700 710 720 730 740 750 L. Strow, UMBC 18

September 2002 AIRS Science Team Meeting Mean and Std of Daily Global Bias over 7 days in Sept. 290 280 B(T) in K 270 260 250 1 O − C in K 0 −1 0.3 Std in K 0.2 0.1 800 850 900 950 1000 1050 1100 L. Strow, UMBC 19

September 2002 AIRS Science Team Meeting Mean and Std of Daily Global Bias over 7 days in Sept. 280 B(T) in K 260 240 220 2 O − C in K 1 0 −1 0.3 Std in K 0.2 0.1 1250 1300 1350 1400 1450 1500 1550 1600 L. Strow, UMBC 20

September 2002 AIRS Science Team Meeting Mean and Std of Daily Global Bias over 7 days in Sept. 280 B(T) in K 260 240 220 1 O − C in K 0 −1 0.15 Std in K 0.1 0.05 2200 2250 2300 2350 2400 2450 2500 2550 2600 2650 L. Strow, UMBC 21

September 2002 AIRS Science Team Meeting ARM-CART July 25 Overpass 280 B(T) in K 260 240 220 UMBC CKD2.4 2 O−C in K 0 −2 2 Std in K 1 0 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 22

September 2002 AIRS Science Team Meeting ARM-CART July 25 Overpass, Zoom 280 B(T) in K 260 240 UMBC 2 CKD2.4 O−C in K 0 −2 1.5 Std in K 1 0.5 0 1250 1300 1350 1400 1450 1500 1550 1600 Wavenumber (cm −1 ) L. Strow, UMBC 23

September 2002 AIRS Science Team Meeting L. Strow, UMBC 24

September 2002 AIRS Science Team Meeting L. Strow, UMBC 25

September 2002 AIRS Science Team Meeting PREPQC Sondes, Sept 1−11, Bias and Std 280 B(T) in K 260 240 220 2 O−C in K 0 −2 6 Std in K 4 2 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 26

September 2002 AIRS Science Team Meeting Sonde Stats: Sept. 1−11 280 B(T) in K 260 240 220 1 O−C in K 0 −1 2 1.5 Std in K 1 0.5 650 700 750 Wavenumber (cm −1 ) L. Strow, UMBC 27

September 2002 AIRS Science Team Meeting July 20 Global Bias/Std with Pre−Launch RTA 280 B(T) in K 260 240 220 1 O−C in K 0 −1 2.5 2 Std in K 1.5 1 0.5 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 Wavenumber (cm −1 ) L. Strow, UMBC 28