崇明东滩湿地与上海城市气候特征对比分析

Comparative Analysis on Climate Characteristics of the Chongming Dongtan Wetland and the Urban Areas of Shanghai

基于20102019年崇明东滩湿地与同期的上海近海台站、崇明气象站及市区气象站的温度、湿度、降水观测资料,采用时间同步对比方法,分析了崇明东滩湿地与上海城市不同地区的气候特征,结果表明:东滩湿地由于其地理位置特殊,与上海其他台站比,日最高气温最低、春夏气温升幅最小,日最低气温接近或高于近海台站和崇明城镇的日最低气温,仅低于中心城区的日最低气温,湿地不易升温、也不易降温;由于东滩湿地下垫面性质及周围环境与城市其他台站的不同,没有城市热岛效应、阻碍效应引起的增雨,中雨以上降水概率明显小于其他各站的降水概率,暴雨概率及强降水次数比其他各站分别少68%~75%和70%~81%,表明东滩夏季雨日少于其他各站的雨日,但秋冬季雨日比其他各站多18%~40%,这也是东滩湿地总雨日多的主要原因;东滩湿地不但缩小昼夜温差还缩小昼夜湿差,尤其湿地能降低雨强,致使有雨日逐年平均相对湿度反而比上海其他各站的小。

Based on the observation data of temperature,humidity and precipitation from 2010 to 2019 at stations with different locations and land cover types in Shanghai,e.g.Dongtan Wetland located in Yangtze River Estuary,the climatic characteristics of the Chongming Dongtan Wetland and the different areas of Shanghai are analyzed with the time synchronization method.The results show that,compared with different stations in Shanghai,the special geographical location makes Dongtan Wetland have the lowest daily maximum temperature and the smallest temperature increase in spring and summer.The daily minimum temperature of the wetland is close to or higher than the daily lowest temperatures at offshore and Chongming town stations,but lower than the day lows in the downtown area of Shanghai.This is because the wetland does not easily heat up or cool down.In addition,due to the dominant wetland cover and rural location,no precipitation enhancement caused by the urban heat island effect and obstruction effect has been observed in Dongtan Wetland.Hence,it is clear that the fewer rainy days,smaller precipitation probability above moderate rain,68%75%less frequency of torrential rainfall and 70%81%less probability of heavy precipitation have occurred in Dongtan Wetland than at other stations in summer.On the contrary,there are 18%40%more rainy days in Dongtan Wetland than at other stations in autumn and winter,which leads to the more rainy days of the whole year.Dongtan wetland can not only reduce the diurnal temperature difference but also decrease the diurnal humidity difference.In particular,the wetland can weaken precipitation intensity so that the annual relative humidity averaged in rainy days is smaller than that of other stations in Shanghai.