Development of Snow Cover Indicators for Canada

Snow cover is an essential climate variable related to water availability, spring flooding, habitat, tourism and transportation. The nature of snow cover makes it have a significant influence on ecosystem and hydrological process. Snow cover is also an important component of the Earth's radiation balance due to its highly reflective nature. Indicators of trends in the temporal and spatial patterns of snow cover are increasingly used to both monitoring climate variability and change and to quantify regional environmental conditions. The choice and accuracy of the indicators are often determined by the input snow cover data and monitoring needs. A survey of snow cover indicators is conducted to identify both those that would satisfy user requirements over Canada and the current practice.

Daily snow cover maps at moderate (500m-1km) resolution are required for a wide range of modelling and monitoring applications, including generation of snow cover indicators for local and regional environmental studies. A data assimilation system is developed using the Canadian Meteorological Centre (CMC) daily time step snow depth model coupled with the Canada Centre for Remote Sensing (CCRS) AVHRR snow albedo model to produce continuous daily snow cover maps at 1km resolution. Inputs to the assimilation system include the operational CMC snow depth analysis, the Environment Canada Global Environmental Model surface temperature and precipitation analyses and single day NOAA AVHRR top of atmosphere reflectance. The CCRS-CMC daily snow cover dataset with other 3 different data sets, including systematic in-situ measurements, cloud free MODIS snow cover products, IMS daily northern hemisphere snow and ice analysis at 4 km resolution, and the Canadian Meteorological Centre snow depth analysis, are then used to generate the snow cover indicators over a five year period. The indicators are evaluated through their sensitivity to documented input data uncertainties, by comparison to continuous monitored in-situ sites, and through intercomparison. Recommendations for suitable indicators as a function of input dataset, based on the development of Canadian snow cover indicators, are provided.