沙尘天气发生频率对大气能见度方差的影响研究:以北京及其沙尘过往路径典型站点为例

利用1971～2000年北京及其沙尘过往路径典型站点日能见度和各种沙尘天气发生日资料,分析了沙尘天气发生频率与能见度方差的关系.发现当沙尘天气频率减少(增加)1次时,能见度方差就偏强(偏弱)1个标准差.沙尘天气发生频率对日能见度变率的影响主要是通过风速的高频变率实现的,当风速变率偏强(偏弱)1个标准差时,沙尘天气发生频率增强(减弱)约30%,近地面风场的高频变率影响了沙尘天气的产生,从而影响日能见度方差的波动.异常低能见度事件(日能见度距平<-2σ,σ为各站各日能见度距平的标准差)频次与能见度方差之间存在显著的正相关性.风速距平频次增加,使得沙尘天气发生频次增加,从而导致低能见度事件频次上升;反之,异常低能见度事件下降.浮尘、沙尘暴和扬沙与低能见度事件的相关程度是不同的.

Research on Impact of Dust Event Frequency on Atmosphere Visibility Variance:A Case Study of Typical Weather Stations Locating in the Dust Route to Beijing

Relationship between dust event frequency and atmosphere visibility deviation is analyzed by using the data of daily visibility and various dust events in Beijing and other 13 typical weather stations locating in the dust events route to Beijing from 1971 to 2000.Results show that the visibility variance increases a standard deviation in the response to the dust event frequency decrease once.The influence of dust event to visibility comes from the high-frequency change of wind velocity.The change of wind velocity in one standard deviation can result in dust event frequency increasing by 30%.The high-frequency changes of near-surface wind influence the occurrence of dust event,and also the fluctuation of daily visibility deviation.The relationship between abnormal low visibility event and visibility deviation is in significant positive correlation.The increase of wind average distance leads to the enhance frequency of dust event and consequently the abnormal low visibility event.There are different relationships between abnormal low visibility event and floating dust,sandstorm and flying-dust respectively.