宁夏大雾的气候特征及变化

选用1961～2004年宁夏19个主要站逐日大雾天气现象观测资料，分析了宁夏大雾的空间、时间分布气候特征和大雾气候变化的事实。宁夏大雾空间分布为南部多中北部少，高山、城市多，其他地区少；时间分布为夏、秋季节多，冬、春季节少且大雾日数月季分布存在地域差别，北部引黄灌区季节变化差异明显，中部干旱带不明显，南部山区季节变化曲线有两个峰值，分别在春季的3月和整个秋季，春末夏初大雾日数最少。宁夏年大雾日数突变特征不明显，在1961～1995年存在8年左右周期，1995年以后有4年左右的周期变化，目前处在一个相对偏多的阶段。宁夏大雾局地特征十分明显，不同地区大雾日数年变化差异较大，但大雾日数年代际变化特征不明显。

The Climatic Characteristics and Changes of Fog in Ningxia

According to the daily foggy weather observation data of 19 main stations during 1961-2004 in Ningxia, the temporal and spatial distribution of fog, climatic characteristics and changes of foggy weather in Ningxia are analyzed. It indicates that, spatially, the fog days in the southern part of Ningxia are more than that in the central and northern parts. The fog days are more in mountain area and cities than that in other areas. Temporally, more fog days concentrate in summer and autumn. While there are fewer fog days in winter and spring. Fog seasons in the yellow river irrigation area are different. In the central arid region of Ningxia, fog season changes are not obvious. The fog seasonal variation curve in southern mountainous areas has two peaks. They appear in March and the autumn. Fog days are the least in late spring and early summer. The mutation characteristics of foggy days in Ningxia are not obvious. There exist an 8 year period in the period from 1961 to 1995. After 1995, the change period is 4 around years. Currently it is in a relatively plentiful fog period in Ningxia. The regional character of heavy fog is obvious in Ningxia. The fog day changes are different in different regions. The fog day decadal variation are not obvious.