Studies On The Climatic Characteristics And Formative Causes Of The Strong Wind Along The Railway From East Xinjiang To West Gansu

Strong wind is one of the meteorological disasters in China. At the same time, it can cause other types of natural disasters, winds often accompanied by dust, snow storms and other severe weather, it’s a serious threat to people’s daily production and life. The forecast of gale has been one of the important contents of the daily forecast of meteorological department. In recent years, under the background of global climate changes, the strong wind days in most regions of China showed decrease tendency year by year, but in some areas there are still increasing trend, its produced a significant impact the railway and highway transportation. In this paper, it has been by using daily weather observation data of the 12 stations along the railway line in 2001-2013, NCEP / NCAR 2.5o×2.5o, FNL 1o×1o(global reanalysis data),firstly, the spatial and temporal distribution of strong wind and dust weather at different levels were statistically analyzed, and using the statistical method to establish the statistical relationship between the wind and the average wind speed; Secondly, summarize the characteristics of different types of strong winds in the area; Finally, analysis and numerical simulation in two processes in the eastern Xinjiang and western Hexi, and the momentum transfer characteristics in strong wind are analyzed. The main conclusions are as follows:(1)Eastern region of Xinjiang to Qijiaojing represented, annual wind speed is larger, and the strength of the wind and strong winds, have increased significantly, the gale days of most stations are in reducing, wind exist obvious seasonal characteristics, wind in March-June is bigger, more in strong breeze; wind in Hexi Corridor of Gansu Province stand for Hongliuhe and Mazongshan, wind at Hongliuhe are large, except for winter, stations at all levels of strong wind days were in significantly reduced, reduce rate may be concerned with the terrain, its have reduced slowly in mountains, and reduced more rapidly in gobi; dust easily happen in Hexi, the occurrence probability of sand dust weather is usually positively correlated with the magnitude of gale, because strong wind is an important dynamic condition of sand dust weather.(2) According to the circulation situation and weather background in the study area, the statistical characteristics and the typical circulation characteristics of various weather types were analyzed statistically, draw the following conclusions: strong wind process in the region caused by cold air, cold warm currents, low pressure and momentum transfer. In the cold air processes, north and northwest is affected the main path; warm and cool winds can be divided into low West High East, North South high-low type, the type of wind is caused by the rapidly increasing pressure gradient and allobaric gradient between the cold and warm air; thermal low pressure strong wind is divided into southern heat low pressure and Mongolian hot low pressure, mainly for heat low development caused pressure gradient caused by the increasing; momentum transfer wind is high and low dynamic forcing caused by, namely atmospheric three-dimensional mass and momentum adjustment caused the formation of the strong wind. The wind had obvious diurnal variation of heat transfer and low wind momentum, usually rapid heating and high temperatures of the time in the afternoon.(3)Analysis of momentum transfer characteristics of two different kinds of wind cases:In the cold air gale, the momentum transfer appeared after the cold front, and in the momentum of wind, vertical velocity has obvious inversion in the jet stream on both sides, and subsidence zone earlier grounding, and there are scattered high value areas below the potential vorticity area, tropopause goes down, which said that the incursion has high potential vorticity characteristics of atmospheric, and it changes more obviously than the geopotential height. Vertical helicity in the frontal passage effect, sinking performance for the anti-cyclonic at the cold front, it’s still anti-cyclonic sinking at the end effect, while rising in the downstream;In the existence of pure momentum transfer process of winds, high altitude strong baroclinic frontal zone is a prominent feature of the formation of the strong wind, high and low level jet match associated with lower vertical motion. These characteristics are significantly different from the cold air process. In addition, the rise and sink in the area of distribution is not concentrated distribution as cold air, senior high potential vorticity continued to affect the low trough, but the height is limited. In the process of pure momentum, there is cyclone type rising all day in the key area.(4) Numerical simulation of the two wind process based on WRF modelNumerical simulation results show that in the cold air gale process, high momentum transfer ahead of ground gale, the momentum is in the high-level system effect and surface cold front transit caused by secondary circulation under the double influence caused and high momentum high value area by sinking trend under the transmission, it is an important factor in the gale weather process continues for a long time. During the period of sensible heat flux and latent heat flux has a diurnal variation, the sensible heat flux has an increasing trend in the formation of strong winds, the wind after the decrease of latent heat flux is stable. In pure momentum transfer process of winds, strong wind zone in high appear signs transfer began the day before, momentum transfer significantly the day by day, due to the existence of upper level jet, jet axis on both sides of the kinetic energy distribution is not uniform, resulting in high and low level convergence and divergence, the corresponding column of air quality change, and in the low layer produced isallobaric wind, then the wind formate. The sensible heat flux, latent heat flux decreases rapidly in the evening to night, which a certain adverse reason to the occurrence of the pure momentum.