Based on the theory of isentropic potential vorticity(IPV)，a diagnostic analysis of a continuous rain process in the east of  Northwest China in the second ten—day of May in 2005 WaS carried out．The results show that the large circulation background which influenced this continuous rain process was the h Jigh ridge near the Ural Mountain and the continually deepening trough near the Balkhash Lake；this continuous rain process Was caused by the low vortex continually created from the plateau together with the cold air split from the north．Because of the topographic effect of the Tibetan Plateau，the hi sh potential vorticity O11 the isentropic surface was transported to the lower reaches along the north side of the plateau；the high value area of IPV Was closely associated with the precipita·tion area。and the positive value area of IPV Can reflect the movement of the cold air，thus it Call be a significant predictor．

Based on the theory of isentropic potential vorticity(IPV)，a diagnostic analysis of a continuous rain process in the east of Northwest China in the second ten—day of May in 2005 WaS carried out．The results show that the large circulation background which influenced this continuous rain process was the h Jigh ridge near the Ural Mountain and the continually deepening trough near the Balkhash Lake；this continuous rain process Was caused by the low vortex continually created from the plateau together with the cold air split from the north．Because of the topographic effect of the Tibetan Plateau，the hi sh potential vorticity O11 the isentropic surface was transported to the lower reaches along the north side of the plateau；the high value area of IPV Was closely associated with the precipitation area。and the positive value area of IPV Can reflect the movement of the cold air，thus it Call be a significant predictor．

The large range rare fog process which occurred in East China from November 30 to December 4 in 2004 was analyzed, including the circulation background, its adjustment and evolvement, the climatic background, the atmospheric stratification condition and the vapor condition near surface, etc. Results show that the warm advection at the low level, the stable atmospheric stratification and the abundant vapor condition resulted in this rare fog process, and fog dissipation needs the cold air invasion with the cold front.

Based on the "h213 materials of National Meteorological Center and an actual need of the operation and scrv}cc operational system of Lanzhou limited area mesoscale numerical prediction model based on MM5 has   thebeen set up.  A lark    the number of forecasting products arc acquired from the system everyday, which have already become important benchmark for forecasting operation and service，and play more and more important role in elaborate prediction，extreme weather event predic t lon(for example, the torrential rain) and the meteorological geological calamity prediction，ctc.

The new generation of "the synthetical system of operation and service on the northwest drought monitoring and fore
is a synthetical system of operation service which has good physical foundation，stronger monitoring,  prcdicting,and
service abilities, higher automation degree and local characteristic of the northwest region.  Relying on the short一term weather
forecasting, this system gathers the weather information collecting,  processing and information saving for an integral whole,
and takes full advantage of the Internet technique and previous systems, data and information，takes up the systems and pro-
ductions of the other sul〕一special subjects in the item，so that it saves the great capacity of computer space，avoids many rc-
pcated labor, and it brings into play the positive function in the usually monitoring and forecasting service in recent years.