Procedure Research Of The Two Typical Sand-dust Storms Of The Springs In Northern China

Two severe sand and dust storms had occurred during the middle of March in2010and the end of April in2011. Each of them is the strongest one in2010and2011respectively. A preliminary analysis of this severe sand-dust storm was conducted in this paper on the causes, characteristics and inherent mechanism of the sand-dust storm. In order to understand the thermal and dynamic mechanism and information of the scope of sand-dust storm were extracted using MODIS and FY-3satellite remote sensing data. As an innovation, an improved method of remote monitoring sand and dust is then put up to strengthen the previous work.Firstly this paper gives a preliminary analysis of the two sandstorms based on the NCEP/NCAR global grid reanalyzing data, which mainly includes the weather situations and the characteristics of meteorological elements before and after the outbreak of the sandstorms and the dynamic mechanism of the sand blowing and transmitting. And the analysis showed that the main cause of the two sandstorms is the rapid development of Mongolia cyclone. With the interaction of thermal and dynamic factors (the intensive thermal advection and vortex advection), the cyclone moves forward and simultaneously develops successively. Meanwhile, upper trough moves ahead as a result of the deepening of cold advection and the vorticity advection. The region of upward movement in air located in the back of the downwardly transmission of the upper level jet momentum, while the region of downward movement in air located in the front of ones, the both interaction to provide sustained force for pumping dust into the large-scale wind systems. The regions of air instability were coupled with Mongolia cyclone that had moved eastward and developed, where sand and dust easy to move upward during the dust storm. The24h Thermisopleth and Allobaric vary rapidly before and after the sandstorms. The ground is under the control of positive Thermisopleth and Allobaric before the sandstorms. While the sandstorm passes, the temperature falls sharply and air pressure increases remarkably. In addition. The evolution of at cities in china reflected the route、intensity and affected area of dust storm. Secondly, based on a comparative analysis of these two sandstorms, obvious differences among them had be found, such as the strength of affecting weather system, moving path, scope of influence and duration. One cause that leads to these differences is the evolution of upper trough and ridge and that of the surface system. The outbreak area of sandstorms is in correspondence with the development of upper trough and the cyclone, while the intensity and duration of sandstorms is associated with the upper trough’s deepening and with the development of the cyclone. The mutual configuration between upper and lower of the atmosphere makes it easy to transform the baroclinic unstable energy into the disturbance kinetic energy, and while the deepening of the upper trough strengthened the cold air intensity that could lead to outbreak of sandstorm. Factors which combined with sand source region, such as the critical wind speed, upwards area and the wind of700hPa and850hPa, are essential elements in ensuring involvement of dust into the air and long-distance transportation.The ends of in this paper, northern China is chosen as the study area. By analyzing the spectral characteristics of two typical sandstorm case, we determine the bands sensitive to sand and dust (namely1st,2nd and7th band) and combined them to build an index to monitor sandstorms. And with the use of satellite remote sensing, we are trying to detect and locate the sandstorm affected area, and to dynamically monitor the transmission path and strength. The result showed that the sandstorm monitoring images are in accordance with the sandstorm’s affected area using the remote monitoring methods.