Climate Change And Contribution Ratio Of Urbanization In Zhengzhou City For Recent 50 Years

The fact of climate change and its effects has been widely recognized by international community and the scientific community. Human activity and natural changes influence on climate change. Many evidence indicated that the global warming due to human activities over the past 50 years. Human activities led to format the urban climate that is different from the regional climate, and increasingly impact on the urban climate with urban development. The urban climate environment impacts on social production and life directly and obviously. Therefore, the urban climate research not only demonstrate the relationship of human activity and climate change, but also give the practical application to urban weather and climate forecasting, urban disaster prevention, urban planning and urban construction, energy use, population health, environmental protection and the improvement of the ecological balance.In this paper, the records of climatic elements of Zhengzhou from 1951 to 2007 were used. The paper analyzed in Zhengzhou, the trend of changes of various climate factors, mutation characteristics and cycle of changes using statistical methods, least-squares method, M-K mutation testing methods, wavelet analysis methods. The paper compared Zhengzhou climate change with Mengjin climate change since 1961 to analyze similarities and differences of Zhengzhou City and the regional climate change. and analyze causes of climate change, then use the two elements of the rate of change of climate to get the calculation of contribution rate of urbanization on climate change in Zhengzhou City. Major conclusions:(1) The annual average temperature show upward trend in Zhengzhou City since 1951, at rate of about 0.23℃/10 a. From 1951 to the late 80s the temperature was low relatively, but from 1987 to 2007 was high. In period of late 20 years, temperature increases by about 1.6℃, increasing the range of 0.81℃/10 a. The past 57 years, temperatures rising in spring and winter were very obvious, but the rate of warming temperatures in autumn was lower than in winter and spring, warming was not obvious in summer. Cycle of the temperature change is largely inter-decadal cycle. Rate of increase in the average minimum temperature is greater than the highest temperature, the average minimum temperature play a key role in the temperature change. (2) The average rainfall was 640.9mm , The trend of the overall is not obvious from 1951 to 2007 year. Rainfall in the spring and autumn declined ,and the rate of decline of rainfall in autumn was less than the spring, drought in spring had exacerbated the trend; summer and winter rainfall were shown an upward trend. Cycle of rainfall was mainly affected by the inter-annual oscillation.(3) The heat island intensity enhanced 0.31℃since 1961. at 0.065℃/10 rate of increase. Heat island since the late 80's the changes in the value of the more prominent changes in the rate of 0.31℃/10a. Heat island was closely related to urban populations and the number of built-up areas.This meant the urban population increase and urban area expansion was leading to worsening urban heat island effect in Zhengzhou. The urban population number increase was more important than the expansion of built-up area for the enhanced urban heat island effect. There was rain island effect in Zhengzhou City. Rain island effect and urban development was not very significant correlation that did not pass the 0.1 significance level test.(4) Since 1961, warming rate raised by urbanization was 0.064℃/10 a, the contribution rate of the warming raised by urbanization on the temperature increase of Zhengzhou was 25%. Increasing rainfall rate raised by urbanization was 11.16mm/10 a, the contribution rate of the increasing rainfal raised by urbanization on the rainfall increase of Zhengzhou was 82.1%. Urban climate change was influenced by regional climate and human activities together, and the influence and contribution rate of human activities on urban climate was increasing, but the influences and contribution rate on each climate factor was different.