The Analysis Of The Impact Of Urbanization On Summer Precipitation In Jiangsu Province

Urbanization has changed the local dynamics and thermodynamics features, which must have a certain effect on rainfall. Based on a more objective urbanization index, the basic station data in Jiangsu Province, FNL reanalysis wind field data and population, land, the night light data were used to analyse the influence of urbanization on the characteristics of precipitation and the rainfall changes during the different development phase of the cities. The main results are as follows:Urbanization index distribution in Jiangsu Province has the obvious regional characteristics, consistent with thef urban agglomeration types revealed by population, land and lighting data. That is the southern inland of a high degree of urbanization, northern inland of a second degree of urbanization and coastal areas of a lower degree of urbanization. Therefore, this index is of certain accuracy to describe the characteristics of the urbanization and considers the integrated response of temperature and water vapor to urban climate effect Compared to the population, land and the night lights, this index can more ocjectively reflect the physical difference between urban and rural areas.In a approximately weak synoptic flow,most of the precipitation events occurred between afternoon and toward evening. Also, the precipitation days showed a maximum during summer.The results may show a larger fraction of nocturnal events.The rainfall consatration factor analysis revealed that the SW flows yield the greatest rainfall amounts. The W and SW flows produced high mean daily rainfall totals in the N and NE cells, where the urban anomaly apparently maximizes and is climatologically downwind of the nanjing city. It should be noted that the S and SW flows were associated with an "upwind" anomaly, indicating that the complex of urban rainfall effect. Modeling work is still needed to determine which urban factors are most important for altering rainfall.Accumulated precipitation anomaly of a full day analysis revealed that the sizes of the variation trend nearly40years were ranged from southern Jiangsu inland areas of the most urbanized, coastal areas of lowest urbanization, northern Jiangsu inland areas of higher urbanization. The trend of precipitation mainly embodied in the daytime in northern Jiangsu inland areas. In the coastal areas, the rate of changes in rainfall was slightly higher at night than during the day. at night In southern Jiangsu inland areas, the contribution of night rainfall precipitation is much more important than that during the daytime. Compared between the slowly and rapidly developed period of cities, the difference of yearly rainfall, summer rainfall, days of light rain, moderate rain, heavy rain and storm rain was ranged from southern Jiangsu inland areas of the most urbanized, coastal areas of lowest urbanization, northern Jiangsu inland areas of higher urbanization. Visibly, urbanization precipitation effects have been performed by a single city expanding gradually to the urban agglomeration or belt. Regional characteristics are more and more obvious.During the slowly developed period of cities, counties and towns were major parts of northern Jiangsu inland areas. With the development of society, counties and towns were gradually expanded and big cities were spreaded day by day. This transformation may has a more important impact on local precipitation in this areas.