Preprints
https://doi.org/10.5194/tc-2022-230
https://doi.org/10.5194/tc-2022-230
 
30 Nov 2022
30 Nov 2022
Status: this preprint is currently under review for the journal TC.

Does higher spatial resolution improve snow estimates?

Edward H. Bair1, Jeff Dozier2, Karl Rittger3, Timbo Stillinger1, William Kleiber4, and Robert E. Davis5 Edward H. Bair et al.
  • 1Earth Research Institute, University of California, Santa Barbara, CA USA 93106
  • 2Bren School of Environmental Science and Management, University of California, Santa Barbara, CA USA 93106
  • 3Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309
  • 4Department of Applied Mathematics, University of Colorado, Boulder, CO 80309
  • 5Cold Regions Research and Engineering Laboratory, Hanover, NH USA 03755

Abstract. Given the tradeoffs between spatial and temporal resolution, questions about resolution optimality are fundamental to the study of global snow. Answers to these questions will inform future scientific priorities and mission specifications. Heterogeneity of mountain snowpacks drives a need for daily snow cover mapping at the slope scale (≤ 30 m) that is unmet for a variety of scientific users, ranging from hydrologists to the military to wildlife biologists. But finer spatial resolution usually requires coarser temporal or spectral resolution. Thus, no single sensor can meet all these needs. Recently, constellations of satellites and fusion techniques have made noteworthy progress. The efficacy of two such recent advances is examined: 1) a fused MODIS - Landsat product with daily 30 m spatial resolution; and 2) a harmonized Landsat 8 - Sentinel 2A/B (HLS) product with 2–3 day temporal and 30 m spatial resolution. State-of-art spectral unmixing techniques are applied to surface reflectance products from 1 & 2 to create snow cover and albedo maps. Then an energy balance model was run to reconstruct snow water equivalent (SWE). For validation, lidar-based Airborne Snow Observatory SWE estimates were used. Results show that reconstructed SWE forced with 30 m resolution snow cover has lower bias, a measure of basin-wide accuracy, than the baseline case using MODIS (463 m cell size), but higher mean absolute error, a measure of per-pixel accuracy. However, the differences in errors may be within uncertainties from scaling artifacts e.g., basin boundary delineation. Other explanations are 1) the importance of daily acquisitions and 2) the limitations of downscaled forcings for reconstruction. Conclusions are: 1) spectrally unmixed snow cover and snow albedo from MODIS continue to provide accurate forcings for snow models; and 2) finer spatial and temporal resolution through sensor design, fusion techniques, and satellite constellations are the future for Earth observations.

Edward H. Bair et al.

Status: open (until 01 Mar 2023)

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Edward H. Bair et al.

Edward H. Bair et al.

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Short summary
To test the title question, three snow cover products were used in a snow model. Contrary to previous work, higher spatial resolution snow cover products only improved the model accuracy marginally. Conclusions are: 1) snow cover and snow albedo from moderate resolution sensors continue to provide accurate forcings for snow models; and 2) finer spatial and temporal resolution through sensor design, fusion techniques, and satellite constellations are the future for Earth observations.