1) Global Coefficients: Derived from all available cloud-free ASTER scenes for a given network SURFRAD: 246 scenesUSCRN: 371 scenes 2) Day/Night-Specific Coefficients: ASTER scenes grouped by network and daytime or nighttime overpass Upscaling of in situ Land Surface Temperature for Satellite Validation Robert Hale (CIRA/Colorado St. Univ.), Yunyue Yu (NOAA/NESDIS STAR), and Dan Tarpley (Short & Assoc.) Conclusions and Future Activities  At USCRN sites, regression-based upscaling of in situ LSTs can reduce scale-induced errors, thereby rendering in situ LSTs more appropriate for use in validating coarse-resolution satellite LSTs  While statistically significant reduction of error is observed in many USCRN cases, the absolute reduction is typically fairly small (~0.2 K), and SURFRAD sites generally realize little benefit from upscaling  Scale-induced error reduction is highly variable between models and coefficient groups, as well as between individual sites (not shown)  Better performance from more generalized coefficients versus site- specific coefficients suggests lack of ASTER scenes for coefficient determination may be limiting model performance  To address the above, Landsat data are being acquired and utilized for improved model development 2 km x 2 km average LST avg = K Central pixel LST pixel = K LST in situ = K Validation of satellite-derived Land Surface Temperature (LST) poses challenges due both to the paucity of in situ measures against which the satellite-derived LSTs may be compared and because of the mismatch in spatial scale between the two. In an effort to address these issues, multiple linear regression models were derived using high-resolution LSTs from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to characterize the relationship between “point” measurements at ground validation sites and the average LST over a larger area representing a coarse-resolution satellite pixel. The derived models were then used to upscale in situ LSTs from Surface Radiation (SURFRAD) and U.S. Climate Reference Network (USCRN) sites. Unscaled and scaled LSTs were subsequently compared with LSTs from the Moderate Resolution Imaging Spectroradiometer (MODIS). + USCRN (Newton 11SW, GA) Field of View of IRT: 1.3 m SURFRAD (Bondville, IL) FOV of Radiometer: ~30 m 1 km ASTER LST (Stillwater 5WNW, OK; 7/23/2005) Resolution: 90 m MODIS LST (Stillwater 5WNW, OK; 7/23/2005) Resolution: 1000 m Upscaling Model Coefficients GroupSURFRADUSCRN Daytime Scenes Nighttime Scenes ) Season-Specific Coefficients: ASTER scenes grouped by network and climatological season 4) Site-Specific Coefficients: ASTER scenes grouped by individual site SURFRAD: scenes, depending on site USCRN: 4-68 scenes, depending on site GroupSURFRADUSCRN Spring (MAM)5396 Summer (JJA)7296 Fall (SON)80115 Winter (DJF)4164 One-Predictor Regression Model Single ASTER pixel encompassing the ground station used as predictor of large-area average LST Once the  and  coefficients are determined using ASTER scenes, the formula is applied to in situ LSTs to determine scaled values Scaled values then are compared with MODIS coarse-resolution LSTs to determine efficacy of model – reduced standard deviation of differences for scaled vs. unscaled LSTs used as indicator of model performance Standard deviation of differences of MODIS – unscaled or scaled in situ LSTs (K) USCRN Sites (22 sites) Significantly different from unscaled at:  = 0.05  = 0.01 No significant difference for any coefficient type SURFRAD Sites (7 sites) Two-Predictor Regression Model Asheville 13S (NC) Mean NDVI Multi-year average of MODIS NDVI used as additional predictor to better capture seasonal changes in vegetation amount that strongly influence LST Two-Predictor Regression Model (Continued) Significantly different from unscaled at:  = 0.05  = 0.01 USCRN Sites (22 sites) Results at SURFRAD sites similar to those for 1-predictor model – No significant reduction in scale-induced error with any of the coefficient types Air Temperature-Based Regression Model Newton 8W, GA Air temperature used as a proxy for canopy temperature ASTER single-pixel or in situ LST used as indicator of soil surface temperature NDVI used to weight the two temperatures USCRN Sites (22 sites) Significantly different from unscaled at:  = 0.05  = 0.01