Dec 12, 2008 Snow and Ice Products Evaluation C. Grassotti, C. Kongoli, and S.-A. Boukabara

Dec 12, 2008 Assessments Compare MIRS F16 SIC and SWE to FNMOC/NRL operational products, AMSR-E, and National Ice Center IMS on (SRR Action Items #3,7) Seasonal comparisons using NRL, AMSR-E, IMS and GDAS: Jan, Apr, Jul 2008; statistics

Dec 12, 2008 SWE Algorithm Descriptions MIRS computes SWE by comparing retrieved sfc emissivities with those pre-computed from a mw emissivity model for realistic ranges of snow depth and grain size, with volume fraction fixed at AMSR-E uses a brightness temperature (TB) index algorithm to compute snow depth based on TBs at 19 and 37 GHz. SWE is computed from microwave retrieved snow depth and ancillary snow density data. Additional ancillary data for SWE calculation is forest cover fraction (Kelly et al. 2005, reference provided by NSIDC). NRL uses similar TB-based algorithm for deriving snow depth (Kunzi et al. 1982), but computes SWE from derived snow depth and a constant snow density of 0.27 g/cm3 (reference from most recent ATBD)

Dec 12, 2008 Sea Ice Concentration: N. Hemisphere AMSREF16 MIRS MIRS - AMSR F16 NRL MIRS-NRL MIRS-AMSRE NRL-AMSRE : MIRS-NRL agree best over closed ice; NRL-AMSRE agree best at ice edge HSS=0.977 POD=0.989 FAR=0.009 HSS=0.970 POD=0.989 FAR=0.015

Dec 12, 2008 Sea Ice Concentration: S. Hemisphere AMSREF16 MIRS MIRS - AMSR F16 NRL MIRS-NRL MIRS-AMSRE NRL-AMSRE : MIRS-NRL agree best over closed ice; NRL-AMSRE agree best at ice edge HSS=0.958 POD=0.969 FAR=0.018 HSS=0.901 POD=0.893 FAR=0.004

Dec 12, 2008 Sea Ice Conc: Comparison with IMS AMSRE F16 MIRSF16 NRL IMS

Dec 12, 2008 SCE: Comparison with NRL and AMSR-E AMSRE F16 MIRS F16 NRL MIRS SCE comparable to NRL and AMSRE over N. and E. Asia, Scandinavia, N. Canada MIRS SCE underestimated w/r to AMSRE over C. Asia, C. Canada, U.S. AMSRE greater than MIRS and NRL over C. Asia HSS=0.664 POD=0.769 FAR=0.031 HSS=0.599 POD=0.755 FAR=

Dec 12, 2008 SCE: Comparison with IMS AMSRE F16 MIRSF16 NRL IMS False alarms Extensive snow cover Less Extensive snow cover

Dec 12, 2008 SWE: Comparison with NRL and AMSR-E AMSREF16 MIRS F16 NRL MIRS-NRL MIRS-AMSRE NRL-AMSRE

Dec 12, 2008 SWE: Comparison w/ GDAS, NRL, AMSRE AMSRE F16 MIRS F16 NRL GDAS IMS

Dec 12, 2008 SCE Comparison with IMS: F16 NRLF16 MIRS IMS AMSRE HSS=0.693 POD=0.929 FAR=0.018 HSS=0.476 POD=0.850 FAR=0.026

Dec 12, 2008 SWE Comp w/NRL and AMSRE: AMSRE F16 MIRS MIRS-NRLMIRS-AMSRE F16 NRL MIRS comparable (or greater) in northernmost regions MIRS lower in areas of reduced snowpack NRL and AMSRE agree well GDAS

Dec 12, 2008 SCE Comparison with IMS: F16 NRLF16 MIRS IMS AMSRE HSS=0.725 POD=0.771 FAR=0.018 HSS=0.557 POD=0.606 FAR=0.012

Dec 12, 2008 SWE Comp w/NRL and AMSRE: AMSRE F16 MIRS MIRS-NRLMIRS-AMSRE F16 NRL GDAS MIRS comparable (or greater) in northernmost regions MIRS lower in areas of reduced snowpack NRL and AMSRE agree well AMSRE snow line further south in Canada and Asia

Dec 12, 2008 SIC N. Hemisphere: AMSREF16 MIRS MIRS - AMSR F16 NRL MIRS-NRL MIRS-AMSRE IMS HSS=0.925 POD=0.937 FAR=0.013 HSS=0.953 POD=0.972 FAR=0.016

Dec 12, 2008 SIC S. Hemisphere: AMSREF16 MIRS MIRS - AMSR F16 NRL MIRS-NRL MIRS-AMSRE HSS=0.922 POD=0.919 FAR=0.004 HSS=0.965 POD=0.978 FAR= : Largest differences over ice edge

Dec 12, 2008 SWE Comp w/NRL and AMSRE: AMSRE F16 MIRS IMS F16 NRL No NH snow cover in July!

Dec 12, 2008 Seasonal Statistics: Sea Ice Conc. Correlations higher in NH than SH Corr: NRL-AMSR > MIRS-NRL > MIRS-AMSR Std dev varies with icepack seasonal cycle (higher in summer) MIRS-NRL std dev < MIRS-AMSRE generally Larger biases in NH summer SH Summer NH Summer NH: Blue SH: Red

Dec 12, 2008 Seasonal Statistics: Snow Water Equiv. MIRS-NRL correlations higher, std dev lower than MIRS-AMSRE (same sensor) NRL-AMSRE correlation higher, std dev lower than MIRS-AMRE (similar alg?) Biases less than +/- 2 cm

Dec 12, 2008 Summary Compared MIRS F16 SIC and SWE to FNMOC/NRL operational products, AMSR-E, GDAS, and National Ice Center IMS for Jan, Apr, Jul, Nov 2008  Generally: MIRS and NRL products appear similar to one another  SIC: MIRS slightly less than NRL near ice edge in both hemispheres; generally good agreement with AMSR-E  SCE: Good agreement with AMSR-E and IMS except over Asia where AMSR-E higher; differences over N. America  SIC/SCE: MIRS and IMS good qualitative agreement  SWE: MIRS values follow seasonal cycle; Fair agreement in northernmost areas/deeper snowpack; MIRS systematically lower than NRL and AMSR-E in southerly areas/lower snowpack  AMSR-E SWE and SCE greater than both MIRS and NRL over C. Asia/Himalayas; AMSR-E false alarms over U.S. Conclusion: F16 SIC, SCE, SWE sufficient maturity for delivery and operations