Urbanization Effect On Surface Warming In Nanjing

Nanjing is an important economic and science and technology center in east China, so research on the effect of the urbanization is of great significance. We collected station climate data, NCEP/NCAR reanalysis data and urbanization statistics data, basing on the aggregative indicator method combined with Back-propaqation (BP) artificial neural networks, observation minus reanalysis (OMR) method and urban observation minus rural observation (UMR) method to study the urbanization process and its rffects on temperature and humidity environment. The correlation between temperature humidity environment changest and urbanization process had been discussed in this paper.(1) Basing on the urbanization statistics from1985to2010,we used BP artificial neural networks to calculate the weighted value of uebanization index to urban comprehensive standards. The result shows that Civilian car ownership was in the largest rate of contribution, Urban population had little contribution.The urbanization comprehensive index of all kinds cities increased with the interannual variability, especially after2000. And large cities growed most rapidly.(2) Daily mean surface air temperature and relative humidity data from meteorological stations in Nanjing during1980-2009and from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) Reanalysis, were used to investigate the effect of rapid urbanization on temperature and humidity change. The result shows that Nanjing had the most contribution of45.07%to regional average warming trends, and26.8%to the relative humidity decrease trend.All kinds of cities had largest warming trends in winter. Most of the reflect on urban warming was in the increase of minimum temperature. The result of the comparison method beween urban and subueban compared with OMR method was on the low side. It would underestimate the influence of urbanization.(3) The correlation between temperature variation and urbanization comprehensive index were all remarkable, especially in Nanjing. During all the season of the year, correlation was most significant in winter and the worst in summer.Urbanization process and the minimum temperature was notable related, especially in winter. To relative humidity, the correlation only in Nanjing was remarkable. OMR and UMR method all can reflect the effect of urbanization to some extent, but the results of OMR method were more relevant to urbanization process. Among all four index, the correlative coefficient of the temperature and relative humidity in Nanjing were all correlatied with power exhaust and civian vehicles, but urban population were small.