关键词: 宁夏, 雾日和霾日, 趋势分析

Abstract:

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．

Key words: Ningxia, fog days and haze days, tendency analysis