Assimilation of remotely sensed snow data in CALDAS land assimilation system

Snow cover and terrestrial snow processes have a crucial influence on heat fluxes between the land and atmosphere because of its high albedo and insulating thermal properties, which impact the energy and water balance on land. For this reason, special emphasis is put on the modeling of snow processes and on the application of initial conditions for these processes in environmental prediction system (weather and hydrology). The snow water equivalent (SWE) and snow cover fraction (SCF) are of particular importance for accurate representation of sensible and latent heat fluxes in atmospheric model and of water availability in hydrological model. To account for this, a high resolution ensemble Kalman filter (EnKF) analysis scheme has been developed to include observed SWE and SCF into the Canadian Land Data Assimilation System (CaLDAS), to be proposed for operational implementation at the Canadian Meteorological Service in the next year or so. Ultimately, CaLDAS will be integrated into the coupled land-atmosphere system. The main objective of this study is to include the following space-based remote sensing data in CaLDAS for the assimilation of terrestrial snow. Snow remote sensing data by the Advanced Microwave Scanning Radiometer (AMSR-E) produces daily coarse-resolution (25 km) SWE products. The Moderate Resolution Imaging Spectro radiometer (MODIS) provides global snow cover products on a daily basis at a spatial resolution of 4 km, but the SCF only contains partial information about the SWE state. The Interactive Multi sensor Snow and Ice Mapping System (IMS, from NOAA) data are also available on a polar stereographic projection at 4 km resolution which classifies data points as either land, sea, sea ice or snow. As a first step, daily and 5-day average (pentad) passive microwave SWE data for a period from November 2006 to April 2007 will be compared to snow water equivalent data derived from the GEM land surface model through Western Canada (500 - 650 N latitude, 2400 - 2650 longitude) with 10 km resolution covering of the study area (forest, tundra and prairie). A subsequent modeling study to compare the daily MODIS SCF and IMS imageries for spring 2007 with the land surface model output will also be carried out for the same region.