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Heat Analysis and Thermodynamic Effects Part 2

Tham khảo tài liệu 'heat analysis and thermodynamic effects part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 2 The Thermodynamic Effect of Shallow Groundwater on Temperature and Energy Balance at Bare Land Surface F. Alkhaier1 G. N. Flerchinger 2 and Z. Su1 department of water resources Faculty of Geo-Information Science and Earth Observation University of Twente 2Northwest Watershed Research Center United States Department of Agriculture 1The Netherlands 2USA 1. Introduction Within the foregoing half century several studies debated over the effect that shallow groundwater has on land surface temperature Myers Moore 1972 Huntley 1978 Quiel 1975 . As land surface temperature is a key factor when the process of energy and water exchange between land surface and atmosphere occurs we can presume that shallow groundwater naturally affects the entire surface energy balance system. Shallow groundwater affects thermal properties of the region below its water table. Further on it alters soil moisture of the zone above its water table which results in affecting its thermal properties the magnitude of evaporation albedo and emissivity. Hence shallow groundwater affects land surface temperature and the surface energy balance in two different ways direct and indirect Figure 1 . The direct way henceforth referred to as thermodynamic effect is through its distinctive thermal properties which make groundwater acts as a heat sink in summer and a heat source in winter and affects heat propagation within soil profile. The indirect way is through its effect on soil moisture above water table and its related effects i.e. evaporation soil thermal properties of vadose zone land surface emissivity and albedo . Studies that investigated the thermodynamic effect commenced by the work of Kappelmeyer 1957 who could successfully use temperature measurements conducted at shallow depth 1.5m to locate fissures carrying hot water from deep groundwater. Birman 1969 also found a direct relationship between shallow ground temperature and depth to groundwater. Works by Cartwright 1968 1974 Bense Kooi 2004 .