Advisor: Ron Smith
Land-use and land-cover are major factors in the heat budgets on the regional and local climate scale (Dickinson and Henderson-Sellers, 1988; Lyons et al., 1993; Rabin et al., 1990; Zaitchik et al., 2006). In semi-arid and arid regions in particular, changes in water availability dramatically impact the land-cover, which can affect the albedo, surface roughness, the exchange of water, energy and carbon dioxide with the atmosphere, and therefore the surface temperature of the region. This work seeks to determine the effect seasons have on land-cover, the surface heat budget and prevalent land-surface feedbacks in semi-arid regions.
Current efforts have gone into calculating and analyzing the surface heat budget in Northern Wyoming, which is considered to be a semi-arid region and experiences a seasonal drying throughout the summer, fall and winter months. We examine two Landsat 7 ETM images (July 29 and October 10, 2001) of the region and specifically investigate the seasonal impact on the surface heat budget in three different land-cover areas. It was found that the solar contribution of the surface heat budget dominates not only in determining the amplitude of Rn, but also in the overall surface heat budget balance. Despite the fact that the solar contribution decreases by over a factor of two from July to October, the sensible heat flux remains positive and even increases slightly from July to October. This is interpreted to mean that it is possible that a combination of remote sensing and atmospheric sounding data can detect the seasonal drying that typically occurs in Wyoming between these months. The fact that the sensible heat remains positive and increases slightly in October could be due to two reasons: that there is a slight decrease in the latent heat flux and/or that the surface is heated from the soil below, elevating surface temperature.
Future work includes producing a more accurate description of the surface energy budget by more accurately calculating the values of the surface and atmospheric emissivities and the surface wind speed. Efforts will also be made towards including heat transport and storage terms into a simplified heat budget equation. Another goal is analyze the surface heat budget of July and October images in Northern Wyoming from earlier and later years. This will further test whether a combination of satellite images and sounding data can capture the seasonal drying typical of this state and it will determine if the increase in the sensible heating is dominated by heating from the soil or a reduction in the latent heat flux or a combination of the two. We plan to calculate this region’s heat budget separately using North American Regional Analysis Data. This comparison analysis will determine the accuracy of heat budgets estimated by satellite images. Eventual comparisons of images from different seasons and other semi-arid regions from around the world will contribute to answering the question of how the Earth’s surface changes with variations in climate and what feedbacks play a dominant role.
15 May 2009