An Analysis Of The Temperature Range And The Warming Effect Of Urbanization In China Regions

The phenomenon of the global warming has been universally acknowledged. According to the IPCC report, the globally averaged mean air temperature has increased 0.6℃ during last century. Some asymmetric characteristics between diurnal increase and nocturnal increase is found in the process of the surface temperature increase, in which the increment of the maximum temperature is less than that of the minimum temperature although both the maximum temperature and the minimum temperature increase in most areas. As a result of it, the diurnal temperature range (DTR) decreases. The global warming can be seen not only in the increase of the mean air temperature, but also in the change of extreme temperature, which has caused huge loss in recent years and has been paid extensive attention by many governments. The global warming is widely known as an impact of human activity on climate because many observation stations in the world locate in big cites or the outskirts of big cites. In order to make clear these problems, it is necessary to analyze the characteristics of the mean air temperature and the extreme temperature, and the impact of urbanization on air temperature is also worth investigating.In this thesis, the characteristics of the temperature range and the warming effect of urbanization in China areas in the background of the global warming are studied. Although some previous work has given analysis about the characteristics of DTR and the warming effect of urbanization in China, the detail features of DTR, monthly temperature range (MTR), seasonal temperature range (STR) and annual temperature range (ATR) are not present sufficiently because different area has different geography and climate feature in China. So, it gives the author the motivation to investigate these characteristics in different areas in China. Additionally, the existing work in the impact of urbanization on the mean airtemperature is almost confined to periods before 90's at last century, and the workin the urban heat island (UHI) during last decade is insufficient up to now, especially the analysis of urbanization effect on extreme temperature is scarce. Based on existing work in this field, the author tries to present some detail characteristics in the points given above.It is found that the monthly, seasonal and annual mean DTR all show decreasing tendencies generally and also have some regional features, which have the most decrease in the Northeast China and the Sinkiang province, and the least decrease in the North China. When it comes to the details characteristics, the MTR decrease most obviously at the end of winter and in spring; and the STR has the most obvious decreasing tendency in summer; to the ATR, most regions in China decrease significantly, and the Northeast China has the steepest decrease.The analysis of urbanization proves that the obvious warming effect of urbanization exits in China. The annual extreme values of the maximum and the minimum temperature in cities are both higher than those in rural areas. On the contrary, the DTR in cities is less than that in rural areas. The difference of the annual temperature extremes between cities and countries decreases in summer and increases in winter. The averaged warm days and cool days in cities are all more than those in countries. And the same result appears in the averaged warm nights and cool nights. In both cities and the rural areas, the obvious decrease is found in the number of the longer DRT days, and the inverse tendency is seen in that of shorter DTR days. The impact of urbanization on the minimal value of the extreme temperature is stronger than that on the maximal value. But to the DTR, the relation is inversed. The UHI is more obvious in the north of China than in the south of china. And in the north of China, the North China is affected the most weakly by UHI. It is interesting that the UHI is the weakest in summer and autumn, but the strongest in winter in the north of China, which is contrary to that in the south of China.Additionally, the UHI also...