Based on the numerical prediction interpretation techniques and forecast experiences，the short － term objective forecast system
of meteorological elements for Northwest China is established． With the aid of meteorological data of real － time observation，the
verification and assessments of objective forecast from the system － output for air temperature and precipitation in winter of 2006 have
been performed． The results show: ( 1) The forecast accuracy of maximum and minimum temperature is much higher than that of precipitation
with the accurate rates of 70% and 34%，respectively． ( 2) The factors affecting the forecast accuracies of temperature and
precipitation are the static stability of atmosphere and relative humidity． ( 3) If the system established on month scale，the forecast accuracy
of temperature is expected to have a 10% improvement．

The change of the 0℃level height in summer over the northeast side of the Qilian Mountain was analyzed, and the relationshipbetween the 0 `C; level height and surface temperature, precipitation, water vapor content in atmosphere and stream flow of inland rivers were discussed. Results show ; (1) The 0℃level height was obviously higher than normal in the late 1950s and the 1960s, and lower in the 1980s. It presented downward irend from the late 1960s to 1970x, and upward trend in the 1980s and 1990x, and it downward again in the first 4 years of the 21 s2 century; ( 2 ) From May to September, the positive correlation was found between the 0℃level height and surface temperature, water vapor content in atmosphere, and it was negatively correlated with precipitation, and there was low correlation

Based on the data of aerological and surface meteorological observation for many years，the trend of water vapor content and its transport over Lanzhou city were analyzed deeply. Results are as follows：（1）The water vapor content and its transport are relatively more in summer than that in winter，and the water vapor content increases from Feb to Jul，decreases from Sep to Jan，and keeps invariable in Jul and Aug；nearly 97% water vapor content concentrates below the height of 400 hPa；（2）The trend of water vapor content distinctly corresponds to the change of precipitation，rainy days and temperature，but also there are some differences；（ 3 ）Over Lanzhou city，the large center of water vapor transport is near the height of 500 hPa，the maximum diurnal variation of water vapor is at the layer of 700 ～ 600 hPa in winter，and these are obviously different from those over the east of China.