Characteristics Of Temperature Change And Surface Type In Pearl River Delta Under The Background Of Urbanization

The process of urbanization of land use changed greatly,in order to study the impact of temperature by urban planning and construction,provide basic information for the planning and construction of eco-city.The results were as followed.Combined with land use and land cover data as well as NDVI data in recent 30 years(1983-2012),the monthly temperature data set of 27 stations over Pearl River Delta was used to analyze the trends of annual/seasonal/daily range for average temperature,average maximum and minimum temperature,respectively.In addition,the effect of urbanization and the spatial variation of temperature over Pearl River Delta was also analyzed.The following conclusions:1)The variation of annual mean temperature in Guangzhou,Foshan and Huizhou all showed rising trend in the past 50 years,and the temperature increased by 1.85,1.85 and 1.15?,respectively.The warming mainly began from 1984 and the warmer years increased significantly,and the warmer seasons mainly occurred in autumn.2)In recent 50 years,average temperature,average maximum and minimum temperature increased significantly mainly in the region around the urban stations,and the warming of average minimum temperature was most evident.The rate for daily range of urban and suburban stations was negative and tended to decrease.After the reform and opening(1979-2012),the warming rate in Guangzhou,Foshan,Huizhou and Longmen was much faster than that in recent 50 years,and the variation of average maximum temperature was most evident.The daily range of Guangzhou and Foshan still exhibited decreasing trend,which was slight compared to the trend in the past 50 years.While,the daily range of Huizhou and Longmen showed increasing trend,which was significantly different from the trend in recent 50 years.In terms of the seasonal variation,the warming mainly concentrated in autumn and winter.3)In the past 50 years,the annual average temperature and average maximum temperature in the central region is much higher than surrounding area,and showed the state that South was higher than that in North.The warming area coverage and intensity of the average minimum temperature was more significant than that for the annual average temperature and the average maximum temperature.After the reform and opening,for the annual average temperature,the average maximum temperature and average minimum temperature,the high-warming region significantly expanded and the intensity also increased compared to recent 50 years.The warming mainly concentrated in Panyu and Shunde.The diurnal temperature range in most of the Pearl River Delta region was negative,and only Conghua,Zengcheng,Zhuhai and Kawashima showed weak positive trend.After the reforms,the area of diurnal temperature range with positive value expanded with increased intensity.4)In recent 50 years,for the average temperature and average minimum temperature in Guangzhou,Foshan and Huizhou,the effect of urbanization was positive,indicating that the urban heat island effect caused the raise of ground temperatures.In terms of daily range,the effect of urbanization was negative,indicating that the decreasing of daily range was caused by the urbanization.After the reform and opening,the impact of urbanization on average temperature in Guangzhou,Foshan and Huizhou was more evident.The impact of urbanization on the daily range was reduced compared with that in the past 50 years,which was partly owing to the urbanization.5)After the reform and opening,as the rapid urbanization of the Pearl River Delta region,the urban construction area consistently increased,while the farmland and green area was significantly reduced.ND VI index in most areas showed a decreasing trend,corresponding to that temperature showing evident warming trend at the same time.In Guangzhou and Foshan,the correlations between NDVI and average temperature,average maximum temperature and average minimum temperature,respectively reached-0.59 or more,showing a moderate or high degree of correlation.6)Taking Zhuhai as representation,the result of relationship between temperature and population over Pearl River Delta showed that the correlation coefficients between lnP(population logarithmic)and annual average temperature,average maximum and minimum temperature were 0.60,0.64 and 0.55,respectively(all passing the significance test at level of 0.01),showing a moderate degree of correlation.