Through a time series analysis of atmosphere visibility from 1960 to 2004 in the 13 cities of Xinjiang, the following
regional meteorological facts are found.
1) Atmosphere visibility has changed in some yearly trends and seasonal fluctuations. With some exceptions of the
cities of Hetian, Akesu and Shihezi, an increasing trend of atmosphere visibility from the middle 90s to the present is
shown clearly in other 10 cities of Xinjiang. Atmosphere visibility in summer and winter is much better than that in
spring and autumn. It indicates that Xinjiang urban air conditions have been greatly improved in this period.
2) Atmosphere visibility is regionally increasing from the north to the south. Particularly, in northern Xinjiang, the
change trend of atmosphere visibility in winter is similar to that in the whole year. However, in southern Xinjiang, the
change trends of atmosphere visibility in spring, summer, and autumn are similar to that in the whole year.
3) Atmosphere visibility is closely related to the Normalized Difference Vegetation Index (NDVI). The larger the
NDVI is, the higher atmosphere visibility is. From 1981 to 2003, atmosphere visibility and the NDVI are synchronously
increasing with some trivial fluctuations.