What won't explode?

Sandstorm refers to a weather phenomenon in which strong winds drag a lot of dust into the air from the ground, making the air particularly turbid and the horizontal visibility is lower than 1 km. The formation of sandstorms requires conditions such as dust on the ground, strong winds and unstable air conditions. Sandstorms can cause houses to collapse, traffic power supply to be blocked or interrupted, fires, human and animal casualties and so on. And pollute the natural environment and destroy the growth of crops.

Based on the data of CALIOP/CALIPSO and OMI/Aura satellites, combined with HYSPLIT backward trajectory model, the upper air flow field distribution, vertical distribution of dust aerosol and transport air trajectory during three sandstorms in northwest China in late April, 20 10, 2013 in 2009 were analyzed.

Mongolian cyclone and cold front are the main systems leading to dust weather. In the middle and lower troposphere, dust aerosols are mainly distributed in 0 ~ 7000 meters under the mixed weather system, moving from west to east.

Under the pure cold front weather system, dust aerosols are mainly distributed in 0~4000 meters, moving from west to southeast; When the two weather systems are the strongest, the vertical distribution height of dust aerosol is above 3000 meters, the depolarization ratio is about 0.5, and the dual-wave signal ratio is above 1.0.

When the dust weather weakens, the vertical distribution height of dust aerosol is 0~2000 meters, the depolarization ratio is 0.3, and the dual-wave signal ratio is about 0.8. The main vertical distribution height of dust aerosol in mixed weather is 3000~7000 meters, which is higher than that of pure cold front dust particles.

The weather situation favorable to strong winds or strong winds, favorable distribution of dust sources and favorable air instability conditions are the main reasons for the formation of sandstorms or strong sandstorms.

Strong wind is the driving force of sandstorm, and the source of sandstorm is the material basis of sandstorm. Unstable thermal conditions are conducive to the increase of wind power and the development of strong convection, thus carrying more dust and winding it higher.

In addition, drought and lack of rain in the early stage, warming weather and rising temperature are the special weather and climate background for the formation of sandstorms; The convective cells before the ground cold front develop into clouds or squall lines, which is a small and medium-sized system conducive to the development and strengthening of sandstorms. The topographic condition conducive to the increase of wind speed, that is, the narrow tube effect, is one of the favorable conditions for the formation of sandstorms.