The Impacts Of Urbanization On Climate Change In Hefei

With the development of urbanization,urbanization and its effects on regional climate have been attracting more and more concern.In this study,method of comparison between urban and suburbs,and historical analysis were used to analyze the differences of temperature,wind speed and precipitation between urban of Hefei and its adjacent suburbs.In addition,the correlation and principal component analysis were used to analyze the nine urbanization indicates,including total population,the second industry output,etc.,then the index of urbanization was calculated to indicate the degree of urban development.Then a regression model between urbanization index and meteorological factors was constructed to study the effects of urbanization on climate change and its contribution and to reveal the comprehensive relationship between urbanization level and regional climate change.The results are as followed:(1)There were high positive correlations among the nine development indicators of Hefei city,and the levels of urbanization increased with time: 1972 ~ 1995 was stable development stage and 1995~2012 was rapid development stage.(2)Temperature in Hefei and its suburbs increased from 1972 to 2012,and the increase rate in city of Hefei was higher than that in the suburbans.The effects of urbanization on the annual mean temperature,minimum and maximum temperature were0.05?/10 a,0.18?/10 a and 0.06?/10 a,respectively,the contribution rate of urbanization on the annual minimum temperature was the most prominent,up to 38%.The impact of urbanization on temperature was seasonal.The warming rate in spring and winter was higher than in summer,in particular,the increase of the minimum temperature in spring was the more prominent,up to 0.72?/10 a,which was two times higher than that in summer.70s and 80 s are the cool temperature periods,and the rapid rise in temperature begins at the 1990 s.The sudden change in temperature of Hefei station was earlier than in suburbs.(3)The annual precipitation of urban and suburban decreased,and the decreasing rate in city was faster than that in suburban.The annual precipitation was mostly high in the 80 s,20 century and 10 s,21century.The annual precipitation was low in 90 s,and the changes in the suburbs and urban areas were basically the similar.As a whole,summer is the rainy season,and winter is the dry season,spring and fall is between them,and the precipitation in spring is more than that of autumn.The precipitation is maximum in Julyand the minimum of precipitation is in December of Hefei urban and suburban.The cumulative rainfall in Hefei has quasi 8~16a,quasi 4~8a and quasi 2~4a scale periodic changes.Among them,the small-scale periodic of quasi 2 ~4a is the strongest and the most significant.(4)The annual average wind speed both in urban and suburbs decreased,and in the city decreased more.The monthly average wind speed in urban was lower than that in suburbs.In twentieth century,70 s and 80 s have high value of wind speed,21 century and10 s have low value period.The average wind speed of Hefei city was less than that of suburbs every month.The maximum of average wind speed is present in April both urban and suburban,and the minimum is present in October.The overall shows a seasonal distribution,which the spring wind speed is high,while the autumn wind speed is low.(5)The regression models between urbanization indicators and climatic factors about urban and suburban area of Hefei indicated that annual mean minimum temperature was significantly affected by urbanization,however,there was not significant difference between annual precipitation and urbanization indicators.In the regression coefficients,the output of the second industry had impact on the mean minimum temperature,followed by industrial output,and the industrial emissions was minor.The effect of demographic indicators,economic indicators and living electricity and other urban development indicators for climate factors showed a positive correlation,while green coverage area for air temperature and wind speed was negative.