宁夏雾日和霜日的变化趋势分析

利用1961～2012年宁夏22个气象台站逐日天气现象、能见度、相对湿度资料，采用气候倾向率、趋势系数、最大熵谱分析、突变分析等方法，分析了宁夏各区域雾日数和霾日数的空间分布及变化趋势。结果表明：宁夏雾目数、霾日数均呈南北多、中间少的空间特征，但雾日数南部最多，而霾日数北部最多。近52a来，雾日数除南部山区呈不显著的减少趋势外，其他3个区域均呈增多趋势，而霾日数各区域均呈显著的增多趋势；另外，二者均有明显的阶段性演变特征，1961—1980年为明显偏少阶段，1981～2000年为波动变化阶段，2001年以后为明显偏多阶段；雾日数具有较明显的准7．5a,4．3a周期振荡，霾日数具有较明显的准4．6a、3，0a周期振荡；各区域雾日数与霾日数均未发生突变现象。

Tendency Analysis of Fog Days and Haze Days in Ningxia

Based on the daily fog days, haze days, visibility and humidity data at 22 observational stations from 1961 to 2012 in Ningx- ia, the spatial distribution and variation trends of the fog days and haze days were analyzed by using the climatic inclination rate, maxi- mum entropy spectrum technique and Mann - Kendall test. The results show that the spatial distribution of the annual mean fog days in Ningxia presented an asymmetry saddle. The fog days in the southern and northern region were more than that in the middle region. The spatial distribution of the annual mean haze days was similar to the fog days, but the haze days in the northern region were slightly more than that in the southern region. In recent 52 years, the fog days presented decline trend in the southern region and increase trend in the northern and middle region, but the haze days showed a significant increase trend in all regions. Moreover, both the fog days and the haze days existed obvious change in phase. They were significantly less from 1961 to 1980, fluctuated during 1981 -2000, but be- came obviously more after 2001. There were obvious quasi -period oscillation for the fog days and the haze days. Among, the former were 7.5 and 4.3 years, while the latter were 4.6 and 3.0 years. Neither the fog days nor the haze days had occurred mutation.