安徽省不同等级雾和重度霾时空分布特征及地面气象条件比较

Comparisons of spatiotemporal distribution characteristics and surface meteorological conditions for fog and heavy haze events of different levels in Anhui province

中文关键词:  强浓雾  重度霾  时间一致性  风向风速  降温幅度

英文关键词:Extremely dense fog  Heavy haze  Temporal consistency  Wind speed/wind direction  Temperature decrease range

中文摘要:

      雾和霾都是低能见度天气，生成条件相似。利用安徽78个地面站逐时观测资料，基于雾、霾发生物理条件，建立了不同等级雾日和重度霾日的观测诊断方法，重建了不同等级雾和重度霾的时序资料。根据各站强浓雾发生的同步性，将安徽分为5个雾、霾分布特征不同的区域，探讨了各区域不同等级雾及重度霾出现时地面气象条件的异同。结果表明：（1）安徽省强浓雾主要是辐射雾。强浓雾、浓雾和大雾空间分布形势大体一致，淮河以北东、西部和江南都属于强浓雾高发区，但各地强浓雾的时、空分布特征和影响系统不同；重度霾有明显的北多、南少、山区最少的分布特征。（2）强浓雾年变化呈双峰型分布，峰值在1月和4月，日变化为单峰型，峰值在06时；而重度霾年变化为单峰型，峰值在1月，日变化为双峰型。（3）在强浓雾的高发时段（02—08时），强浓雾时降温幅度最大，比重度霾平均高1℃，风速显著偏低，超过75%的样本风速低于1.5 m/s，且无明显主导风向；而重度霾时，风速比雾时明显要大，个别区域有超过75%的样本风速大于1.5 m/s，且以西北风到东北风为主。说明重度霾能否演变为强浓雾的关键地面气象因子是风速、风向和降温幅度。

英文摘要:

      Fog and haze are low visibility weather with similar formation conditions. Based on hourly observations collected at 78 surface stations in Anhui province and physical conditions favorable for fog and haze formation, a set of methods are established to diagnose fog days of different levels and heavy haze days. The time series data of fog days of different levels and heavy haze days are reconstructed. According to the synchronization of extremely dense fog events at each station, Anhui province was divided into five regions with different distribution characteristics of fog and haze, and the similarities and differences in surface meteorological conditions for different levels of fog and heavy haze in each region are discussed. The results show that: (1) Extremely dense fog in Anhui mainly belongs to radiation fog. The spatial distributions of extremely dense fog, dense fog and fog are basically the same. The region to the north of the Huaihe River and the region to the south of the Yangtze River are high incidence areas of extremely dense fog, but the spatial and temporal distribution characteristics and influence weather systems of extremely dense fog are different between the regions. The distribution characteristics of heavy haze show high occurrence in the north, low occurrence in the South and the least in mountainous areas. (2) Annual variation of extremely dense fog shows a bimodal pattern with peaks occurring in January and April; daily variation is unimodal with the peak at 06:00 BT; the annual variation of heavy haze is unimodal with the peak in January, and the daily variation is bimodal. (3) During high incidence period of extremely dense fog (02:00—08:00 BT), the meteorological condition is characterized by large temperature decrease range (TDR) with the average TDR 1℃ higher than that during heavy haze period, significantly low wind speed that is weaker than 1.5 m/s without obvious dominant wind direction for more than 75% of the samples. During heavy haze events, the wind speed exceeds 1.5 m/s for more than 75% of the samples in some areas, which is significantly higher than that during fog events. Dominant wind directions are northwesterly, northerly and northeasterly. It indicates that wind speed, wind direction and temperature decrease range are the key surface meteorological factors for heavy haze to evolve into extremely dense fog.