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Preliminary

Preliminary Analysis of Relative MODIS Terra-Aqua Calibration Over Solar Village and Railroad Valley Sites Using ASRVN. A. Lyapustin, Y. Wang, X. Xiong, A. Wu. AERONET-based Surface Reflectance Validation Network (ASRVN).

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Preliminary

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  1. Preliminary Analysis of Relative MODIS Terra-Aqua Calibration Over Solar Village and Railroad Valley Sites Using ASRVN A. Lyapustin, Y. Wang, X. Xiong, A. Wu

  2. AERONET-based Surface Reflectance Validation Network (ASRVN) Challenges of SR validation: surface is variable, upscaling from ground/tower data to ~1 km satellite footprint is challenging; field campaigns are expensive and rare etc. ASRVN provides continuous val. data at satellite spectral and spatial resolution with great space/time statistics. Main Functions Collect MODIS, MISR … data for 50 km subsets Processing: - QA Analysis - Atmospheric Correction ~ AERONET Aerosol & WV • Products (1 km, gridded): • Parameters of RTLS BRDF model • Surface Reflectance (+swath)/Albedo/HDRF • Spectral Regression Coefficient • (SRC=0.47/2.1 for aerosol retrievals) • 4. Planned: PAR & shortwave irradiance Wang, Y., A. Lyapustin, J. Privette, B. Holben et al., ASRVN Science and Validation Dataset, TGARS, 2009. Lyapustin, A., Y. Wang, R. Kahn, J. Xiong et al., Analysis of MODIS-MISR calibration differences using surface albedo around AERONET sites and cloud reflectance. RSE, 107, 12-21.

  3. ASRVN: Quality Assurance - I MODIS TOA RGB BRF NBRF CM AOD Cloud Mask: Reproducible spatial pattern indicates clear conditions Aerosol Filter detects contrails, thin cirrus cloud and non-homogeneous aerosols Cloud Shadows CM Legend Blue – Clear Yellow – Possibly Cloud Red – Cloud White -Snow Dark Red – Cloud Shadow Cyan – Water Grey – Aerosol Filter Snow Mask Standing Water Mask (dynamic LWS mask)

  4. ASRVN: Quality Assurance – II (CM enhancement from aerosol retrievals)  Water Cloud model =0.8, High % of Coarse mode I  I TOA Reflectance  =0.2, Low % of Coarse mode =0, Fine mode , m Red SWIR Blue AOT  AOD R7 RTLS7 CM TOA RGB NBRF BRF Resolving thin clouds using Cloud Model (yellow color)

  5. Method of Analysis • Time period May – October to reduce effect of clouds and surface change due to rain and snow (at RRV); • Use 10×10 km2 average for SV and 5×5 km2 average for RRV shifted off-center; • Use geometry normalized BRFn based on known Ross-Thick Li-Sparse (RTLS) (reduces angular variation by a factor of 3-6): • AOTBlue<0.4

  6. Results: Railroad Valley TMS

  7. Results: Solar Village TMS High scatter

  8. Results: Annual Mean Aqua-Terra Solar Village Railroad Valley

  9. Conclusions • The used SV and RRV sites have seasonal and interannual variability and are used for a relative Terra/Aqua characterization; • On average, B1, B2, B4, B7 show lower relative change over time between Terra and Aqua; • Bands B3, B5 of MODIS Terra show a clear trend with respect to Aqua: Terra B3 decreases with time (SV – high scatter, 0.011/0.24~6% RRV), while B5 increases with time (0.016/0.48~3.3% SV, 0.008/0.39~2.1% RRV). • Need proper separation of view angles for RVS analysis. • Need updated subsets with frame number; RRV subset shifted by ~14km east; 12 CEOS Desert Cal. Sites.

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