North China enters "rainy mode"! How strong is this precipitation process? How to deal with it?

At the beginning of the "July-August" period, many places in the north quickly switched from sunny mode to rainy mode.

The Central Meteorological Observatory predicts that from the night of July 20 to the 23rd, moderate to heavy rain will occur in eastern North China, Huanghuai, eastern Inner Mongolia and Northeast China, with torrential rain in some areas. The State Flood Control and Drought Relief Headquarters launched a Level 4 emergency response at 16:00 on the 20th for Beijing, Tianjin, Hebei and Haihe flood control and drought relief headquarters. The China Meteorological Administration also launched a Level 4 emergency response for major meteorological disasters (rainstorms).

Image source: China National Meteorological Administration

How strong will this precipitation process be?

Why does one-third of the annual rain fall in the north in just one month?

In meteorology, "the end of July and the beginning of August" generally refers to the period from late July to early August each year, when precipitation is most concentrated in North China and Northeast China. It is also known as the "North China Rainy Season". According to the flood control standards for the rainy season, sometimes the "on-duty" time of "the end of July and the beginning of August" can be extended to the second half of mid-July to the second half of mid-August, about a month.

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In just a month or so, the rainfall in northern China will account for about one-third of the annual rainfall. North China, the Huanghuai region, Northeast China, and Shaanxi, Gansu, and Ningxia on the Loess Plateau will all experience the most concentrated rainfall of the year.

The reason is mainly due to the "subtropical high pressure" behind it. Around late July every year, the summer monsoon advances northward to North China, and at the same time, the subtropical high pressure ridge of the northwest Pacific Ocean rises northward to the area north of 30° north latitude. The subtropical high pressure is like a water vapor "conveyor belt", which continuously transports water vapor on the ocean surface to the north, providing sufficient water vapor conditions for North China. These warm and humid air currents "love and hate" the cold air moving eastward and southward, bringing heavy rainfall to the northern region.

Of course, the occurrence of rainstorms is also inseparable from the topography of the mountains: the Taihang Mountains stretch from north to south across the central part of North China, and are the natural dividing line between the Loess Plateau in the east and the North China Plain. They have an important impact on the weather system in North China, especially rainstorms. For example, the rainstorms in Beijing from July 19 to 21, 2016, were related to the forced lifting of water vapor and warm and humid air by the Taihang Mountains.

Compared with the rainy season in the south, which lasts for more than 20 days, the rainy season in the north can be described as "extremely thirsty", and it takes a year to finally have enough food to eat during the rainy season. It can be said that during the "July to August" period, the rain in the north is hitting the "KPI".

Although the overall rainfall is strong, it does not stand out from the overall statistics of the rainy season in North China from the end of July to the beginning of August. Fang Chong, chief forecaster of the Central Meteorological Observatory, said that judging from the current forecast conclusions, the extreme nature of this rainfall process is not very strong and is not uncommon in North China.

Heavy rains have caused more floods.

How to protect yourself during the period of July to August?

Rainfall in the northern river basins is concentrated and intense, making this period also the time when flood disasters are most concentrated in the north.

What should you pay attention to when traveling during a rainstorm? How to take precautions during a thunderstorm? How to save yourself when a flash flood comes?

Click ↓↓ to learn more about disaster prevention and risk avoidance! Let's take correct precautions and spend the flood season safely~

Comprehensive sources: Xinhua News Agency, China Central Meteorological Observatory, Beijing Evening News, etc.