Spring is a season of revival and change. During this season, we often encounter some special weather phenomena, such as sandstorms, strong convection, cold air, etc. These weather phenomena will not only affect our lives, but also bring us some surprises and beautiful scenery. On April 12, it seems that the weather in the central and eastern parts of the mainland is relatively average, with large areas of clear skies in the north and a small range of rainy weather in the south, but in fact, large areas of thick clouds in Xinjiang have already shown signs of imminent weather changes.
1. The Mongolian sand storm is about to reappear
The cold clouds in Xinjiang are the result of a violent oscillation of the westerly wind belt, which led to the formation of a strong westerly trough and is already approaching the mainland of Xinjiang. The forecast of the Central Meteorological Observatory pointed out that on the 12th, there was moderate to heavy snow or sleet in some high-altitude areas in northern Xinjiang, and there were local blizzards or heavy snowfall.
After the westerly trough swept over Xinjiang, it cut off and formed a cold vortex system to move eastward and southward, and gradually induce extratropical cyclones over the Mongolian Plateau. An extratropical cyclone is a weather-scale baroclinic low-pressure weather system that lacks both tropical and polar features and is often accompanied by fronts. The activity of extratropical cyclones and cold vortices will lead to a rapid increase in winds in Mongolia and the northern part of the mainland, and a large amount of sand will be carried from Mongolia to the mainland.
For example, the forecast of the Central Meteorological Observatory pointed out that there will be a sand and dust weather process from west to east from northwest China to North China: on the 13th, sand and dust affected eastern and southern Xinjiang, western Inner Mongolia, western Gansu and Ningxia, among which there were sandstorms in southern Xinjiang and some parts of western Inner Mongolia; on the 14th, there were blowing sand or floating dust affecting central Inner Mongolia, Ningxia, northern Shaanxi, northern Gansu, northern Shanxi, and northern Hebei; starting in the early morning of the 15th, affecting Beijing, Tianjin, In the central and southern parts of Hebei Province, there was floating dust weather, and on the afternoon of the 15th, the dust weather process ended.
Second, the sand and dust may blow into the south of the Yangtze River!
In fact, some forecasts even point out that a large amount of yellow sand will move further south with the wind, for example, the numerical forecast of the China Meteorological Administration indicates that on April 15, the sand and dust that will move south with the wind will reach the south of the Yangtze River on the mainland.
In recent years, it is common for sand and dust storms in Mongolia to transport to the mainland, and it usually occurs in spring, especially from March to May, and is one of the most common sand and dust weather in the northern part of the mainland. Its formation and development are mainly influenced by extratropical cyclones. The westerly wind belt is a prevailing wind blowing from west to east in the mid-latitudes, blowing from the high pressure area of the subtropical high pressure belt to the polar region. Fluctuations often occur in the westerly wind belt, forming troughs (low pressure) and ridges (high pressure). The trough line in the westerly wind belt is called the westerly trough. The westerly trough is a strong dynamic system that can stimulate atmospheric instability and induce extratropical cyclone systems near the surface, resulting in large-scale gales and dust.
Third, the temperature dropped by more than 12 degrees
It is worth noting that the activity of the westerly trough and cold vortex will also bring a large-scale cooling process to the northern part of the continent. The cold vortex is a small- and medium-scale low-pressure system with a lower central temperature than the surrounding area, with significant rotation, often accompanied by strong convection and precipitation. As the westerly trough sweeps through Xinjiang and gradually cuts off to form a cold vortex, the eastward movement of the cold vortex will also pull cold air into the northern part of the mainland.
The Central Meteorological Observatory pointed out that from April 12th to 15th, there were 4~6 northerly winds in most parts of the north, and the winds in Xinjiang, the central and western parts of Inner Mongolia, and Hexi in Gansu could reach 7~9, and the temperature dropped by 6~10 degrees, and the cooling range in some areas exceeded 12 degrees. This cooling process will occur after the recent warming in the northern part of the continent, which will bring significant temperature fluctuations, so everyone should pay attention to the increase in clothing.
Of course, when the cold air thrown out by the cold vortex is discharged, many places in the northern part of the continent have continued to heat up, and the underlying surface has warmed significantly, and the cold vortex can easily form a vertical structure of the atmosphere with cold at the top and warm at the bottom, thus causing strong convection. It is usually accompanied by strong weather phenomena such as thunder and lightning, high winds, hail, etc. In short, the sandstorm and cooling are caused by the violent fluctuations of the westerly wind belt, which is a characteristic of the spring climate, and everyone should pay attention to the weather forecast and prepare for sand and cold protection.