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Huang_IGARSS2011_VIIRS_Aerosol_JH_20110727.ppt
1. Characterization and Evaluation of NPP VIIRS Aerosol EDR Performance Based Upon Prelaunch Analysis N. Christina Hsu (NASA/GSFC) Istvan Laszlo (NOAA/STAR) Jingfeng Huang (NASA/GSFC, Morgan State University)* Myeong-Jae Jeong (Gangneung-Wonju National University, Korea) David O. Starr (NASA/GSFC) Heather Q. Cronk (IMSG at NOAA/STAR) Hongqing Liu (Dell Services at NOAA/STAR) Robert Holz (UW/PEATE) Min Oo (UW/PEATE) Acknowledgement to: Sid Jackson (NGAS) and other VIIRS Aerosol/Cloud Cal/Val Team Members for valuable feedbacks and discussions, and Raytheon algorithm conversation team for additional data support Email: Jingfeng.huang@nasa.gov
2. VIIRS – Visible Infrared Imager Radiometer Suite VIIRS 24 EDRs Land, Ocean, Atmosphere, Snow * Product has a Key Performance attribute NPP Satellite CERES VIIRS CrIS ATMS OMPS Limb OMPS Nadir
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4. Quality of Coatings, Top of IFA From XtalkTim5_Mills.ppt by Steve Mills (NGST); Courtesy: Chris Moeller. Optical : Dominant VISNIR crosstalk. Linear with signal, spectral and spatial component. Believed to be largely due to filter defects. Magnitude primarily depends on number of defects in spectral filters (‘spits’). Defects from coatings of Integrated Filter Assembly cause large angle scattering. Part I: Sensor Performance 1.1 What is Optical Crosstalk? Quality of Coatings, Bottom of IFA
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9. Part II: Algorithm Performance 2.1 VIIRS-MODIS Comparison 2.1.1 MODIS-Like NOAA/STAR Product ( Science code Drop 4.9.3 ) (Note: MODIS data run through VIIRS algorithm with MODIS LUT at NOAA/STAR; close to final drop of 4.9.4) 2.1.2 MODIS-Like PEATE/LEOCAT Product ( IDPS build 1.5.0.48 ) (Note: MODIS data run through VIIRS algorithm with MODIS LUT at Atmosphere PEATE; It is a relatively old ops code build from 2009 based on Drop 4.9 ) 2.1.3 VIIRS-Like IDPS Product ( Final Drop 4.9.4 ) (Note: a quick glance of VIIRS-Like granules)
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14. 2.1.1 VIIRS (STAR) vs. MODIS: Heavy Aerosol Events Observation of the huge wildfire event over West Russia in August 2010: VIIRS (QA3) is significant lower than MODIS (QA3) when AOT > 1.5. VIIRS MODIS VIIRS MODIS 08/05/10 08/06/10
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23. Q: How comparable are the MODIS Dark Target AOT retrievals to the AERONET AOT retrievals? A: Aqua MODIS DT AOT (Best QA) vs. AERONET AOT (2002-2010). The expected error ranges are ±0.05±0.15AOT for Land, and ±0.03±0.05AOT for Ocean. Land Ocean Backup slide
24. Backup slide: Algorithms VIIRS MODIS Aerosol Models 5 Static Aerosol Models (Dust, Smoke-High Absorption, Smoke-Low absorption, Urban-high absorption, Urban-low absorption), each with 1 fine and 1 coarse mode, model determined from observation Dust in combination with regional fine mode models,13 fine mode fraction Dynamic selection of 2020 possible over-ocean aerosol models, with 4 fine and 5 coarse modes and 101 fine mode fractions 200 combinations of 4 fine model, 5 coarse mode and 10 fine mode fractions, same models Input Bands 412, 445, 488, 672, 2250 nm 470, 667, 2130 nm 672, 746, 865, 1240, 1610, 2250 nm 466, 553, 667, 855, 1240, 1640, 2130 nm Cloud Mask Internal + VCM Internal Aggregation Conduct aerosol retrieval at IP level first, then aggregate AOT to EDR level (40% top, 20% bottom) Aggregate L1B surface reflectance to L2 resolution first, then do aerosol retrieval (50% brightest and 20% darkest for land, 25% and 25% for ocean)
26. MODIS-Like VIIRS (10km) QA=best (3), using best QA (0) only from IP (1km) MODIS (10km) QA=3 VIIRS(PEATE): Heavy Aerosol Case on 2009.182.1500 (Aqua) VIIRS IP (1km), QA=best (0),degraded (1): It seems the heavy aerosol pixels were degraded. VIIRS IP Cloud Confidence Flag: It seems the region is fairly confidently cloud free. VIIRS IP bad SDR qualify flag: All seems good SDR. VIIRS IP AOT out of range quality flag: Only a small portion seems to have AOT out of range. The question is: why those heavy aerosol pixels were degraded from QA=0 to QA=1 at IP level? It seems VCM is not the cause, bad SDR is not the cause either, nor the AOT range, BUT THE VOLCANIC ASH! VIIRS IP VOLCANIC ASH
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Comparison of VIIRS(ABI) and MODIS aerosol AOT retrievals with those from AERONET. The VIIRS(ABI) retrieval is an adaptation of the VIIRS aerosol algorithm for the Advanced Baseline Imager (ABI) to be flown on GOES-R. (Over water the VIIRS and ABI algorithms are (almost) identical. The VIIRS retrievals use gas-corrected 10-km “aerosol” reflectances from the standard MODIS aerosol product. This makes comparison of MODIS and VIIRS AOT straightforward since sampling and spatial resolution of the products are the same, differences in cloud masks and gas absorption are avoided. The MODIS and VIIRS(ABI) retrievals are compared to AERONET Level 2 data using the matchup procedure of Ichoku et al. (satellite retrievals from a 50-km square area around the AERONET site, and 1-hour average of AERONET measurements centered on the satellite overpass). The comparisons cover the period from 2000 to current date from Terra and from 2002 to current date from Aqua. All available ocean/island sites are used. Top row: scatter plot of satellite vs. AERONET AOT, color coded according to the fine mode fraction; MODIS on the left, VIIRS(ABI) on the right. The two heavy dashed lines represent the expected envelope of . The shorter dashed line is the linear fit; the thin solid line is the 1:1 to line. Bottom row: comparison of binned AOT, whiskers represent the standard deviations. MODIS and VIIRS(ABI) retrievals are very similar. VIIRS(ABI) has somewhat smaller overall bias, possibly due to better modeling of wind speed dependence of surface reflectance (fixed in MODIS, variable in VIIRS). Outliers at small AOT include both fine and coarse mode aerosols.
