Modeling snowpack evolution in complex terrain and forested Central Rockies: A model inter-comparison study
Abstract
The timing and amount of spring snowmelt runoff in mountainous regions are critical for water resources and managements. Correctly capturing the snow-atmospheric interactions (through albedo and surface energy partitioning) is also important for weather and climate models. This study developed a unique, integrated data set including one-year (2007-2008) snow water equivalent (SWE) observations from 112 SNOTEL sites in the Colorado Headwaters region, 2004-2008 observations (surface heat fluxes, radiation budgets, soil temperature and moisture) from two AmeriFlux sites (Niwot Ridge and GLEES), MODIS snow cover, and river discharge. These observations were used to evaluate the ability of six widely-used land-surface/snow models (Noah, Noah-MP, VIC, CLM, SAST, and LEAF-2) in simulating the seasonal evolution of snowpacks in central Rockies. The overarching goals of this community undertaking are to: 1) understand key processes controlling the evolution of snowpack in this complex terrain and forested region through analyzing field data and various components of snow physics in these models, and 2) improve snowpack modeling in weather and climate models. This comprehensive data set allowed us to address issues that had not been possible in previous snow-model inter-comparison investigations (e.g., SnowMIPs). For instance, models displayed a large disparity in treating radiation and turbulence processes within vegetation canopies. Some models with an overly simplified tree-canopy treatment need to raise snow albedo helped to retain snow on the ground during melting phase. However, comparing modeled radiation and heat fluxes to long-term observations revealed that too-high albedo reduced 75% of solar energy absorbed by the forested surface and resulted in too-low surface sensible heat and longwave radiation returned to the atmosphere, which could be a crucial deficiency for coupled weather and climate models. Large differences were found in simulated SWE by the six LSMs during both accumulation and melting phases, but had different characteristics for the Niwot Ridge site and for the GLESS site, which may depend on interannual variability of atmospheric forcing conditions. Long-term data at these two sites were used to conduct detailed analysis of surface energy and water budgets in the canopy, and on the snow and soil surfaces to identify major deficiencies in those models. Large-scale (comprising Rockies in Colorado and part of Wyoming and New Mexico) 2-D simulations undertook in this effort helped to assess the performance of models not only for high-elevation forested regions, but also for valleys and plains covered by short vegetation. We also investigated the effects of radiation variability induced by small-scale terrain slope on snow melting and resulted runoff.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H43A1178C
- Keywords:
-
- 1814 HYDROLOGY / Energy budgets;
- 1833 HYDROLOGY / Hydroclimatology;
- 1843 HYDROLOGY / Land/atmosphere interactions;
- 1847 HYDROLOGY / Modeling