It will rain every day in the future... What is the "cold vortex blue" that dominates the Beijing sky?

Review expert: Ye Haiying, deputy director of the New Media Center of the Meteorological Publicity and Science Popularization Center of the China Meteorological Administration (China Meteorological News Agency)

The sky in Beijing is so beautiful these days! Under the azure sky, white clouds are floating, exuding a hint of coolness. Netizens vividly call it "beautiful blue sky". In addition, the temperature and humidity are lower than before, and the cool autumn weather is instantly embodied.

Beijing Science Center under the cold blue sky

This kind of blue sky is called "cold vortex blue" in meteorology. This unique weather phenomenon not only allows the public to enjoy fresh air and beautiful blue sky, but also arouses everyone's curiosity about cold vortex. Why does such a unique weather phenomenon as "cold vortex blue" exist? What impact will it have on us?

What is "Cold Vortex Blue"

Cold vortex

Before talking about cold vortex blue, let’s first talk about what cold vortex is.

Cold vortex is the abbreviation of low-level cold vortex, which is a low-pressure system with a cold center that exists in the middle and upper levels of the troposphere . It is usually formed in the high-altitude trough of the westerly belt. When the cold advection strengthens and penetrates into the trough, it is possible to cut off the trough line and form a closed low-pressure system.

Cold vortex source: Central Meteorological Observatory

In China, low vortices that have a greater impact on the weather can be divided into two categories: one is the sub-weather scale vortex generated by the special terrain of the Qinghai-Tibet Plateau, such as the southwest vortex in Sichuan and the northwest vortex near Qinghai Lake; the other is the cold vortex from high latitudes that carries a lot of cold air, such as the Northeast Cold Vortex, in addition to the Mongolian Cold Vortex, the North China Cold Vortex, etc. The cold vortices that affect the Beijing area can be mainly divided into the Northeast Cold Vortex and the North China Cold Vortex according to the different locations of their centers.

"blue"

After talking about the cold vortex, let’s talk about “blue”.

The formation of the "cold vortex blue" sky is mainly due to the cold air and clear weather brought by the cold vortex . The northerly airflow thrown out from the back of the cold vortex will make the sky blue, and with the formation of stratocumulus clouds, light cumulus clouds and other white clouds caused by unstable air disturbances, the beautiful blue sky and white clouds meteorological landscape will be grandly staged. The cold air will also lower the temperature, sweeping away the previous high temperature and sultry weather.

Characteristics of cold vortex

Rain rushes

I wonder if you are curious about the recent weather in Beijing. Why does it rain so quickly? The rain comes and goes so quickly. This has to do with the two characteristics of cold vortices: cold air masses and counterclockwise rotation .

This mainly refers to the cold closed low-pressure circulation system that exists in the middle and upper layers of the troposphere in mid- and high-latitude regions. The temperature near the center of the cold vortex is significantly lower than the surrounding area. Since the cold vortex is a closed circulation, its guiding airflow is weak and its movement speed is relatively slow, so it can have a long-term impact on a certain area. Sometimes when a cold vortex meets a subtropical high, it is likely to cause heavy rain. The cold vortex rainstorm is very rapid, it falls cleanly and stops cleanly, which explains the previous question, why the rain in Beijing is always so hurried recently.

What impact will the cold vortex bring?

Severe convective weather

Cold vortices not only bring blue skies, but can also trigger precipitation, especially severe convective weather , so they require special attention. Cold vortices can guide dry and cold air from mid- and high-latitudes southward. When the lower layer warms up due to warm advection and solar radiation, unstable stratification of "cold on top and warm on bottom" and "dry on top and wet on bottom" is often formed, resulting in short-term heavy precipitation, thunderstorms, hail, and even tornadoes. When cold vortices appear over North China and Northeast China in spring and summer, they are extremely harmful to agricultural and animal husbandry production.

Kind tips

Thunderstorm

In the next few days, North China will continue to be affected by the cold vortex. You can continue to enjoy the beautiful "cold vortex blue" scenery. The weather has also changed from the previous hot and humid weather. However, due to the characteristics of the cold vortex, the Beijing weather forecast from August 14 to 20 will include the word "thunderstorm" every day. Thunderstorms are frequent, so please remember to pay attention to the upcoming weather forecast and warning information. At the same time, the temperature at noon is still relatively high, so you still need to prevent heatstroke and sun protection outdoors .