A cold vortex storm is coming. What are its characteristics? How to defend?

From 2 1, there will be a heavy rainfall process in North China, Huanghuai and the south of Northeast China. This heavy rainfall was mainly affected by the cold vortex in the upper air, which is also called the cold vortex rainstorm. According to the analysis, this round of rainfall has a long duration, strong rainfall potential and large accumulated rainfall, which should be strictly guarded. So, what is a cold vortex rainstorm? What are its characteristics? What are the difficulties in prediction and defense? What is the difference between its formation and the rainy season in North China? Around these problems, the reporter interviewed Sun Jun, the leader of the innovation team of rainstorm forecasting experts of China Meteorological Bureau and the chief forecaster of the Central Meteorological Observatory.

What is a cold vortex rainstorm?

Sun Jun introduced that the so-called cold vortex is a cold vortex system rotating at high altitude, and its central temperature is lower than the surrounding temperature, so it is called "cold vortex". Correspondingly, like a typhoon, its central temperature is higher than the periphery, which is a warm vortex.

Cold vortex rainstorm is a rainstorm formed under the control of cold vortex. Cold eddies frequently appear in Inner Mongolia and Northeast China in late spring and early summer every year, which often pass through or affect this area repeatedly.

Taking the process starting from 2 1 as an example, the cold vortex originated in the Mongolian Plateau, which is located a little south compared with the positions that often appear in the northeastern and northeastern Inner Mongolia. Falling southward to the North China Plain, coupled with other favorable meteorological conditions, formed this relatively strong precipitation.

Will the cold vortex bring rain?

The answer is no, not every cold vortex process will be accompanied by heavy rain, which requires certain weather conditions.

"The high-altitude cold vortex is a high-level system, which is obvious in the middle layer of the atmosphere, that is, near 500 hectopascals, which is equivalent to a height of about 5,000 meters. It is necessary to cooperate with the low-level weather system to produce a relatively strong rainstorm, such as the process started at 2 1. The role of low-level vortex is very large. " Sun Jun said.

After the cold vortex fell to the North China Plain, a relatively strong vortex system appeared in the lower layer, which is what we call the low-level vortex system, that is, the cooperation between the low vortex and the upper and lower layers, which provided the possibility for the weather conditions of heavy rain. The formation of vortex is mainly related to the forcing of high-altitude cold vortex and the topography of North China, and also related to the release of latent heat caused by precipitation.

After the formation of the vortex, the transport conditions of warm and humid airflow in the southwest of the vortex are very good. In addition, because the warm and humid airflow is warmer, the cold vortex is colder, and the cold and warm air are superimposed, the structure of upper cold and lower warm is formed, which is easy to cause atmospheric instability and helps to form better atmospheric instability conditions. At the same time, the south and east sides of the cold vortex converge strongly, which triggered the occurrence of heavy rain. Based on these factors, heavy rain appeared. It can be said that vortex plays a greater role in this process.

Why is the intensity of this rainstorm strong?

Sun Jun said that the key lies in the strong warm and humid air flow in southwest China.

According to the observation, the wind speed associated with low-level vortex reaches more than 20m/s, and it is a very strong process when the general wind speed reaches12m/s.. Meteorologically, it is called southwest low-level jet, which is as rare as this, reaching 20m/s in history. Strong water vapor and power bring more rainfall. Like the "July 212 rainstorm" and the "July 20 rainstorm" of 20 16, the warm and humid airflow in the southwest is also very strong.

Is it just the cold vortex that affects the rainfall in Northeast China and North China in late spring and early summer?

The answer is also no.

There are many factors that affect rainfall in North China in late spring and early summer, and cold vortex is only one of them. Sun Jun introduced that sometimes the southwest vortex goes northward, which will also affect North China, such as "July 2 1 torrential rain"; There is also a high-altitude low-pressure trough system crossing the border, which will also bring heavy rain; And the eastward movement of the northwest vortex will also affect North China. Another example is the "July 20" rainstorm last year, which formed a high-level vortex system in North China because the plateau low-value system moved eastward. It has different properties and structures from the northeast cold vortex system.

Among these systems, which system has the greatest influence on the rainfall in Northeast China and North China? Sun Jun's answer is: not necessarily, but it is mainly the northeast cold vortex system in late spring and early summer.

In addition, we all know that late July to early August is the main rainy season in North China, and the rainfall at that time was mainly affected by the northward push of monsoon and the northward lift of subtropical high. Therefore, this rainfall is essentially different from the main rainy season rainfall of "seven drops and eight rises".

What are the characteristics of cold vortex rainstorm?

Generally highly dispersed and unpredictable.

Sun Jun introduced that during the cold vortex rainstorm, due to the obvious contrast between cold and warm air, this weather is characterized by strong local rainfall and sometimes scattered rainfall. In addition, the process is very intense, often accompanied by strong convective weather such as thunderstorms and hail. However, if the low-level vortex system is strong, like this process, there will also be large-scale heavy rain and heavy rain.

In forecasting, forecasters still focus on numerical forecasting, which is the basis of weather forecasting. Secondly, according to the conceptual model of rainfall generated by cold vortex, combined with the configuration of high and low altitude, further judgment is made. In addition, forecasters will make predictions by comparing similar cases in history.

Why is the cold vortex rainstorm scattered and difficult to predict? Sun Jun introduced that the cold vortex system is relatively large, with a diameter of over 500 kilometers, so the precipitation weather caused by it is widely distributed on the surface. However, the scale of the vortex affecting the rainstorm is relatively small, with a diameter of about 200 kilometers. In this system, the contrast between hot and cold is strong, the unstable state is unevenly distributed, and the conditions that trigger precipitation are unevenly distributed, so it shows strong locality. Although there may be precipitation in a large area of North China, there may be precipitation in Beijing and not in Tianjin. Beijing is big, Tianjin is relatively small, and even different districts in Beijing are very different, and the locality is more prominent. Therefore, it is necessary to strengthen the short-term approaching forecast through satellite observation and radar observation.

How to defend against cold vortex rainstorm?

Cold vortex rainstorm weather is difficult to defend because of its strong locality and dispersion, small rainfall area, but strong convection, and sometimes short-term heavy precipitation. Sometimes, although the rainfall is not large, it falls in a short time, which is also very disastrous.

Sun Jun introduced that in order to defend against such weather, people and materials should be prepared first. On June 1 day, Beijing entered the flood season, so it is necessary to do a good job in information officer training, material preparation, early warning information release and emergency response. In addition, we should pay attention to the forecast and early warning information released by the meteorological department in time. "Even if your area is not covered by rainfall forecast and warning, it is only around it, but because of the strong dispersion of this rainfall, you must pay attention to the forecast and live information in time."

Besides, don't listen to false information spread through informal channels on the Internet, Sun Jun added.