Climate variability analysis over Canadian boreal and subarctic areasderived from three satellite databases
Abstract
Due to their homogeneous and continuous characteristics, the time series of satellite data allow one to follow the evolution of environmental processes associated with global climate change such as global warming or short climate cycles such as El-Niño/La Niña and the Northern Atlantic Oscillations. We analysed three databases over Canada: (i) the ten-day 8 km resolution composite Pathfinder AVHRR Land Database (PAL, NOAA/NASA) from 1981--2000; (ii) the EASE-Grid SSM/I -- DMSP 25 km resolution passive micro-wave data from 1987--2001; (iii) and the NSIDC EASE-Grid weekly snow cover extent database from 1967--2001. From the PAL data, a new method has been developed to estimate the length of the growing season using smoothed NDVI temporal profiles, land-surface temperature variations and the associated cumulative growing degree-days. Snow cover extent and annual snow-cover cycle are retrieved from the relative winter/summer variation of the SSM/I 37 and 19 GHz brightness temperature gradient. These parameters permit the mapping of Canada's large ecosystems and the monitoring of the spatio-temporal variation of the phenological cycles of vegetation as well as the snow-cover cycles, the latter being correlated with climate change obtained from meteorological data. For the last the last twenty years, results show that over the North (> 55^o N), a warmer and longer growing season(associated with a longer period without snow) is detected. However in south eastern Canada, we observe a colder and shorter growing season with no trend in snow cover, while in the West (> 100^o W) a longer period without snow is noted. For 1966 to 2000, the period without snow increases by +0.5 day/yr for Canada overall. Finally, the satellite signal clearly reveals the El Niño / La Niña cycle in western Canada. The significant regional variations derived from the satellite time series retrieval of land-surface biogeophysical parameters are discussed in the context of global change studies. Key words : extraction of land surface parameters, temperature, NDVI, snow cover extend, climate cycles, global warming, Canada.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....7677R