Impact of climate variations on surface albedo of a temperate grassland

Albedo controls surface energy balance and affects the microclimate conditions of ecosystems. Changes in albedo could induce significant changes in climate. Anthropogenic and natural factors, such as land cover and land use change, could result in the albedo change of land surfaces. In this study, we used Moderate Imaging Spectroradiometer (MODIS) data and climate station observations to investigate the albedo patterns of a temperate grassland (Grasslands National Park, Canada) and its changes due to the impact of climate variations. Our study focuses on 3 years of data (2001-2003), each of which had a different climatic regime. In 2001, precipitation fell well below its historical mean, and drought severely affected agricultural production over the GNP region. In 2002, annual precipitation was well above its historical mean, although most of the precipitation fell in the late growing season and drought conditions still occurred in the early growing season of the year. In 2003, annual precipitation was slightly lower than its historical mean, but more precipitation fell in the early growing season. MODIS and climate station observations suggest (a) during the winter-to-summer and summer-to-winter transitional periods, air temperature plays an important role in determining the surface albedo by controlling snow absence and presence; (b) in the winter season, the amount of precipitation (snow) greatly affects the surface albedo, of this ecosystem; (c) in the growing season, ecosystem water conditions can significantly alter the surface albedo of the semiarid grassland through their impact on plant growth and ecosystem conditions. These results show that surface albedo changes of this temperate grassland highly respond to climate variations. The results of this study have a number of implications in weather forecasting, climate change, and ecosystem studies. Our results stress the importance of (a) accurately simulating snow coverage fractions in regions where snow cover tends to exist throughout a long winter season, and thus, has a large influence on surface albedo; (b) accurately simulating temperatures during seasonal transitional periods (winter-summer or summer-winter) since they determine the dates that snow covers the land surface and, in turn, strongly impact on simulations of surface albedo; (c) explicitly linking the impacts of climate change with variations on surface albedo, and the feedbacks of the albedo response to the physical climate system, in the climate model projections. (c) 2006 Elsevier B.V. All rights reserved.