| The effect on climate by human activities is the key part of climatology, while urban climate is a special local climate formed by hurman activities and unbanization, under the background of regional climate. More and more anthropogenic heat has been emitting into environment since a huge amount of energy is consumed each day by urban residents and city construction. Shanghai, the international commercial center, one of which main characteristics in its rapid development is the change of the original land use function. A dense population, crossing roads, intensive high structures, etc consist the particular underlying surface, which causes a more severe urban heat island with the urbanization’s getting ever more acute.Analysis in this paper started from multiple time sacle by wavelet and EMD, and then problems were brought out to the exploration into the function of underlying surface in urban climate. Softwares including ENVI, IDL and ARCGIS were used to help gain the complete information of constructures, based on which urban anthropogenic heat emittion and the relationship between urban temperature and the usage of air-conditioning both in qualitative and quantitative were made. Finally the data of land use categories in ARWWRF was modified to made numerical simulation cases and contrast experiments with UCM coupled. The main conclusion can be drawn as below.(1) Researches show that general temperature changes in recent 136 years of Shanghai is a steady increase, with a faster rate than ever in the last 3 decades. Secondly, the main fluctuation cycles are around 70 years, at which the temperature mainly shows four stages as cold-warm-cold-warm. The warmer period in 1940s’ and the colder period in 1960s’ made up the main features of temperature changes in 20th century in Shanghai. Lastly, a quasi-periodic oscillation of 2 years was also found to exist. At multiple time scales, noticeable abrupt changes of temperature lie in late 1920s’ and 1959s’.(2) Main variation law of precipitation in recent 136 years of Shanghai is oscillations at micro-scale including 2-3a,5a,8-10a and 40a, among which 40a is the most obvious, especially during the middle 20th century. The precipitation is in ascend phase at larger time scale but just the opposite for those under 20a scales.(3) Wavelet and EMD methods were used to gain multiple scale analysis of Shanghai heat island both in winter and summer of year 2004 and 2009 respectively. Results shows good corresponding relationships between the wavelets’ center oscillation and generation of heat island, displaying obvious diurnal variations in both winter and summer under different time scale. Heat island always happens in evening and midnight in winter, while it turns stronger in the afternoon in summer, which is in accordance with the characteristic of its being weaker in spring and summer but stronger in winter and autumn. Meanwhile, with the effets of urbanization, the value of heat island of 2009 is 0.4-0.5℃higher than that of the year 2004, and the increasment in summer is bigger than in winter.(4) With the help of ENVI, IDL and ARCGIS, Shanghai aerial photograph was processed to obtain complete digital information of structure distribution and height in Shanghai, which help to build the basis of researches on urban anthropogenic heat emission and the land use data in ARWWRF. The urban and built-up land was enlarged according to the digital data, which is tally with the actual situation.(5) 50 years’ month average temperature data of 11 districts in Shanghai was analyzed, as a result, temperature difference of every 5 years between each station and Chongming was got, showing the extend of heat island from city center to rural areas, especially from 1980’s,20th century, with a larger increase of difference in temperature. On the basis of existed theories, one of the main mechanisms of heat island generation, anthropogenic heat emission, was analyzed. All possible heat resources and facilities in urban were studied and categorized based on the flow chart, then methods of calculating and concluding of 3 phases were compared for different purposes. Heat emitted by carbon and fuel in recent 30 years were calculated respectively in order to estimate the total amount of anthropogenic heat. Meanwhile, annual average temperature of both downtown and suburb and temperature difference were analyzed, which is proved to be positively correlated to anthropogenic heat. Spacial distribution of anthropogenic heat emission in Shanghai was gained according to the special distribution of industrial area, constructures and roads.(6) Finally, effects on temperature by the usage of air-conditioning in summer Shanghai were studied. Based on digital construction distribution information of Shanghai, supposing a relativity between floors and air-conditioning density, heat emission by air-conditioning has a quite good consistency with surface temperature retrieval, which was also proved to be one of the main reasons of the high temperature in Shanghai city.(7) With UCM coupled, numerical simulations of wind field, temperature, and other characters of PBL in spring of Shanghai were made by ARWWRF with both original and modified underlying surface data. Results showed that horizontal wind velocity decreases obviously, displaying the urban dragging effects. Meanwhile, the vertical wind velocity increases, and tends to be bigger affected by surface warming effects. The higher temperature centers appear at the downwind direction by the effects of surface wind fields. Surface temperature and PBL height are both closer to the observation values.(8)To make further sense of the effects on urban climate by urbanization, different experiements were designed. Results showed that, with modified land use data, UCM coupled and anthropogenic heat added, temperature simulated is the closest to the observation values. Simulation values of areas represented city center, surbub and urbanizing land are close to the observation values both in winter and summer, with correlation coefficient R larger than 0.9. In the light of influence extent of the 3 factors on urban temperature, the order should be UCM＞underlying surface landuse data＞anthropogenic heat emission. Heating effects of urban underlying surface is obviously than that of others. Data shows that, within same distance, the increasment of temperature of sea-land breeze passing through urban areas can reach 4.61℃, notably higher than blowing over other surfaces.Urbanization, particularity and the complexity of urban climate can be better and intuitionisticly understood based on above work. Cities, as the living regions of human, have extremely complex internal mechanism, Space-time Distribution and energy exchange function. Rapid urbanization has been turning into one of the major subjects in urban climate, while the statistical menthods and numerical simulations have been brought the important role to play, thus, how to use and modify models rationally is an important scientific issue. |
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