HR: 10:50h
AN: C12A-03    [Abstracts]
TI: Interactions between boreal forest snow water equivalent distribution and atmospheric circulation determined from regional climate model simulations, passive microwave remote sensing, and field measurements
AU: * Derksen, C
EM: Chris.Derksen@ec.gc.ca
AF: Climate Research Branch, Meteorological Service of Canada, 4905 Dufferin Street, Downsview, ON M3H5T4 Canada
AU: MacKay, M
EM: Murray.Mackay@ec.gc.ca
AF: Climate Research Branch, Meteorological Service of Canada, 4905 Dufferin Street, Downsview, ON M3H5T4 Canada
AB: Snow water equivalent (SWE) estimates from the satellite passive microwave data record (1978-present) provide evidence that the snow cover regime over the northern boreal forest of western Canada is characterized by an interannually consistent band of high SWE values. The snowpack water storage across this region greatly exceeds that found in the dense boreal forest and prairie regions to the south, and the open tundra to the north, and the within- and between season SWE variability across the northern boreal forest is exceptionally low relative to the surrounding biomes. The potential existence of a consistent SWE zone resistant to interannual climatic variability over the past 25 years is intriguing in the context of the sensitivity of high latitude snow cover to climate variability and change. A series of ground sampling campaigns were conducted to evaluate the SWE distribution across the northern boreal forest in northern Manitoba and the Northwest Territories during the 2003/04 and 2004/05 winter seasons. These datasets provide a comprehensive perspective on northern boreal snow cover extending from the Hudson Bay lowlands northwest to the boreal shield environment north of Great Slave Lake (a region with an extremely poor historical conventional measurement record). Data from these surveys confirmed a gradient of lower to higher SWE through the transition from the southern to northern boreal forest, although satellite derived retrievals for the open tundra north of the boreal tree line were consistently low. A series of Canadian Regional Climate Model (CRCM) simulations were conducted to identify feedbacks between the atmosphere and land surface for a domain focused on the western Canadian northern boreal forest. A control simulation produced monthly patterns of SWE distribution that closely matched the satellite passive microwave retrievals. Water budget computations showed the SWE accumulation pattern to be a function of the modeled regional precipitation pattern, and not the result of surface processes such as melt or evaporation/sublimation. Mean monthly patterns of 850 hPa frontogenesis forcing corresponded closely to the patterns of accumulated SWE suggesting lower tropospheric frontal activity was responsible for early winter season precipitation events along a lower tropospheric storm track that preferentially deposited snowfall along the northern boreal SWE band. CRCM sensitivity experiments were conducted with perturbed land cover and terrain. These simulations isolated an orographic role in the frontal development, but no boreal forest steering mechanism could be inferred. The combination of remotely sensed observations, field measurements, and model simulations proved uniquely insightful across a region where snow cover is a temporally persistent feature, but the conventional observing network is extremely sparse.
DE: 0736 Snow (1827, 1863)
DE: 0758 Remote sensing
DE: 1621 Cryospheric change (0776)
DE: 3355 Regional modeling
SC: Cryosphere [C]
MN: Fall Meeting 2005