Quantitative Study On Urban Heat Island Effect In The Arid Land

Urban heat island is the most prominent characteristic of the temperature influenced by activity of human being,and has aroused widespread interests due to its effect on global warming,which therefore automatically leads to a newly-round academic craze on the research of climate, ecology and environment. Urban heat island is an not-unusual phenomenon existing with various degrees in large and medium sized cities around the world; and the arid land is not an exception. With the acceleration of urbanization, urban heat island has gradually flown out of the water in the arid land. The present result is that there is a severe restriction on the city development of Urumqi and the health of its residence, both physically and psychologically due to the phenomenon of Urban Heat, Urban Dry, and Urban Turbidity. Therefore, to choose a city that is large enough and located centrally in the arid land, where Urumqi rightly belongs to, as a prototypical case on the research of urban heat island effect in the arid land contributes vitally and practically on the alleviation of urban heat island effect island effect, reasonable planning of oasis city, improvement of the ecological environment and the life quality of local residence, the maintenance and the promotion of oasis's stable and highly effective sustainable development. Simultaneously, there is a vital scientific significance in further understanding heat distribution difference, the surface-atmosphere system reciprocity and the condition of energy exchange in the arid land in western China.Directed towards the review of advance and shortcoming of studies on urban heat island effect,with the frontier theory of and method of urban geography, urban ecology, urban environment science and urban climatology, urban heat island effect in the arid land are quantitative analyzed through the technological train of 3S and statistics. With meteorological data, EOS/MODIS and Landsat TM/ETM+ data, land surface temperature is retrieval based on split-window and mono- window algorithm, which is taken the main data source. The spatial characteristic of macro and micro temperature distributinon is analyzed in research area and the temporal characteristic of urban heat island effect in day, night, season and year is compared. Based on temperature landscape distribution, change of heat island effect is studied from 1987 to 2005. Then correlative study is taken between urban heat island effect and its influences on the aspects of climate background, urban underlay and man-made heat. Finally simulation and forecast are made on the developing trend of the urban heat island effect in the coming 5 years made use of mathematic model, and then corresponding measures are put forward to relieve heat island effect.The research indicated that there is a remarkable urban heat island effect in Urumqi. The spatial characteristic shows that distribution of urban heat island effect goes in close correlation to the type and function of the underlying surface, and the high-temperature region distribution is associated with urban building and traffics in urban areas, but the corresponding temperature such as water surface, urban green land and farmland is lower. The temporal characteristic shows that the underlying surface of arid suburban is mainly the desert, and the temperature is high during the daytime. Therefore the urban heat island effect is not obvious during the daytime, on the contrary, can appear the phenomenon of urban cold island sometimes. The urban heat island effect in Urumqi is only obvious in the daytime in summer and at night all year round. The maximum intensity of urban heat island happens at night in summer. There is the difference of 4-6℃between urban and near suburban, 8-10℃between urban and far suburban. Urban heat island effect has become more obvious since 1987.On the foundation of classification and regression tree, then superimposed the temperature distribution, the following types of temperature landscape are divided: the-highest-temperature building, higher-temperature building, high-temperature building, high-temperature bare land, low-temperature green land and low-temperature waters. Then the research is further carried out on variations of Urumqi urban heat island effect based on landscape change during 1987-2005. There is the biggest area and its change of higher-temperature building, which increased from 92.81km2 in 1987, 106.73km2 in 1999 to 136.42km2 in 2005. The areas of highest-temperature building and high-temperature building have also increased, and the-highest-temperature building becomes the center of heat island. Through the construction of temperature landscape transfer matrixes and TUPU, as well as the appraisal system of temperature landscape. The following results are discovered: each type of temperature landscape in the city increases continually along with the urbanized advancement. The around high-temperature bare land being the main extended source, the urban heat island effect tends to be spreading. Many landscape indexes have been used to evaluate changes in temperature landscape and theirs shows that the landscape diversity and fractal dimension increased. Heating conglomeration, which formed by heating fragments in the-highest-temperature building represented the heating center.On the base of temporal and spatial distribution and change, the mutual relations among urban heat and its influenced factors are analyzed from points of the city climate background, underlying surface characteristics and artificial heat. The key elements are comparably analyzed such as the air temperature, relative humidity, precipitation, wind frequency and speed of each weather station in Urumqi, the result shows that on the one hand heat island effect affects the change of the key points of meteorological phenomena, for instance, the air temperature and the relative humidity, leading to a more distinctive or notable change of weather factors than other stations. On the other hand, different characteristics, such as floor wind field also promoted or blocked the form of urban heat. At the same time, on the research of the relation between temperature field and underlying surface, urban temperature field is strong or medium minus correlative with vegetation coverage degree, and medium positively correlative with building density degree. Population, energy demand and other man-made heat sources also have some effect on urban heat island effect. Finally, the-highest-temperature building, which is the strong heat island area, is selected to be analyzed, showing that driving factors of area change of the highest-temperature building in the studying area are reduced to man-made heat, economic growth and urban forestation.Finally, cellular automata model based on artificial neural networks is proposed to simplify simulation and forecast process of complex change of urban heat island effect. Forecast on the temperature landscape distribution in 2010 shows that there will be some changes in the part of spatial distribution of temperature landscape in 2010. There will be a certain increase in each type of temperature landscape of urban and rural construction land, a small expansion to around high-temperature bare land, a slightly reduction of urban green land. And waters will still not change much. The partial polymerization of highest-temperature building and the continue expansion of heating center area from 4.62% in 2005 to 5.66% in 2010, will reflected the continual existence of the heat island effect.Basing on the above research and analysis, following the related principle of urban ecology, unifies the characteristic of Urumqi, the research put forward to adjust greenland structure, improve urban layout, reduce man-made heat. The ultimate goal is for alleviating the problem of urban ecological environment radically, and keeping efficient and sustainable development of the urban.