According to the data of ground - based observation from 1951 to 2008 at Dunhuang national standard climate station, the spatio - temporal change of sand - dustweather in Dunhuang area was analyzed. The result reveals that the sand - dust weather obviously decreased. It occurred most frequently in the 1950 s, and in a year, it occurred most in sp ring and least in autumn. The annual wind days decrease and wind speed becoming smallwere the main reasons for sand - dustweather reduction in Dunhuang area. Meanwhile, the circulation causing sand - dustweather there was classifyed in the paper. Amp le resources of sand - dust and regional effects p rovide essentialmaterial conditions for sand - dustweather occurrence.

The strongest cold wave weather occurred on Ap ril 19 to 20 of 2008 in Hexi Corridorwhich influenced by the strong cold air
moving southeastward from West Siberia. The circulation situation evolvement characteristc of thisweather eventwas analysed based on
Micap s data, six hours reanalysis data ( horizontal resolution 2. 5°×2. 5°) from NCEP /NCAR. The 300 hPa high - level jet stream,
500 hPa vorticity, temperature advection and vertical velocity, 700 hPa water vapor flux divergence from 08: 00 Ap ril 15 to 08: 00 Ap ril
20 (60 - 105°E, 35 - 60°N) were caculated. The results show that the onset of the cold wave was related to high - level jet moving
southeastward and strengthening gradually, and the positive vorticity area at 500 hPa was in accord with the frontal zone in front of
trough, which was benefit to the strongest cold airmoving southeastward. The low - levelwater vapor flux divergence distribution influenced precipitation obviously under the cold wave weather condition, rainfall occurred in the area of the minimum value ofwater vapor
flux divergence, and no rainfall but dustweather occurred in the area of the maximum value.