2009年上海浦东新区能见度资料的深度分析——兼论高时间分辨率地面观测资料的应用

利用2009年上海浦东新区气象站高时间分辨率的能见度资料及其同步地面气象要素资料,在气块静力稳定的假设下研究了由于辐射冷却引起的霾或雾在演变的各阶段气溶胶吸湿性增长及其消光系数随相对湿度的变化,结果表明：气溶胶吸湿性增长率f（RH）随相对湿度的增长具有先慢后快平滑连续的特点;气溶胶吸湿性增长率在不同季节有所差异,在夏季和秋季较高,在冬季和春季时较低;平均而言,当相对湿度从40%增大到95%时,气溶胶吸湿性增长率可达6.6;对比国内外实验和观测结果,发现f（RH）随相对湿度的变化曲线与硫酸铵亲水增长相似;在这种雾消散时,随着气温的升高,测量给出的相对湿度值不会立即下降,而是在接近饱和的情况下维持一段时间,然后再迅速下降,其滞后大约为1～2小时。这很可能是测湿元件不能及时反映外界湿度变化所致。

In-Depth Analysis on Atmospheric Visibility in Shanghai Pudong 2009——Concurrently on Applying Surface Meteorological Data with High Temporal Resolution

The absorption of water by ambient aerosols and the influence of ambient relative humidity on the extinction coefficient are investigated under the assumptions that the atmosphere is in static stability during low visibility process caused by radiative cooling using the continuous observations data(visibility, relative humidity,temperature,wind etc.) from Shanghai Pudong automatic weather stations in 2009. The subtle features of meteorological elements are also studied with such high temporal resolution(1 min) data.The results show that the hygroscopic growth factor f(RH) of the extinction coefficient increased continuously with RH and featured a first-slow-then-quick uptrend.The curves obtained from different seasons show that f(RH) was relatively higher in summer and autumn than that in winter and spring. Overall,the average f(RH) in 7 cases could reach to 6.6 when RH increased from less than 40%to 95%. We also present comparisons with other researches in the world,and the result shows that the behavior of the average of hygroscopic growth factor of the extinction coefficient in the cases is similar to the calculated growth factor of the scattering coefficient for ammonium sulfate.Further study also shows that the decrease of relative humidity is lagging about 1—2 hours behind the increase of temperature and visibility, which is conjectured that the humidity sensor fails to change quickly enough to measure the variation of relative humidity of the local air mass.