There is no thunder on typhoon days. Are these two things "incompatible"?

Audit expert: Zhan Mingjin

PhD, Chinese Academy of Meteorological Sciences

This summer, affected by the northward circulation of Typhoon Dusurui, heavy rainfall occurred in Beijing, Tianjin, Hebei and other places. News videos of "cars floating on the ground" and "travel by boat" emerged one after another. Typhoon Kanu, the sixth typhoon this year, also approached the three northeastern provinces, causing increased precipitation and affecting people's daily lives to a certain extent.

Every summer and autumn, we hear about typhoons. As one of the most destructive meteorological disasters in nature, typhoons have a huge impact on people's lives and economic development.

But there is an old saying that goes like this: "When there is thunder and a typhoon passes, one thunder will destroy nine typhoons ." In fact, there is a certain degree of subjective perception in the proverb, but after all, it is the historical experience of the older generation. What is the basis of these proverbs? Will there be thunder during a typhoon?

Source | pixabay

1How are typhoons formed?

A typhoon is a type of tropical cyclone, which is a cyclonic vortex of varying intensities that occurs in tropical oceans. It is a general term for tropical depressions, tropical storms, typhoons or hurricanes.

When the locally accumulated hot and humid air above the ocean rises to high altitudes on a large scale, the surrounding low-level air will flow toward the center and form a tropical cyclone under the influence of the deflection force of the earth's rotation. Internationally, the maximum wind speed near the center is often used as the classification standard: those below level 7 are called tropical depressions, level 11 are called tropical storms, and those above level 12 are called typhoons or hurricanes .

Generally speaking, the formation of a typhoon requires the following two basic conditions:

First, a wide tropical ocean surface. This ocean surface requires not only that the sea surface temperature is higher than 26.5℃, but also that the water temperature at a depth of 60 meters must exceed this value. This is because the main energy source for the formation of typhoons is the water vapor on the tropical ocean surface, and on the ocean surface with a temperature below 26.5℃, it is difficult for typhoons to maintain and develop due to insufficient heat energy. In order to ensure the formation of typhoons, this warm water layer must be about 60 meters thick.

Second, the deflection force of the earth's rotation is large enough. The rotation of the earth will cause the low-pressure area formed by the gathering of clouds to rotate, thus forming a tropical cyclone; as the rotation strengthens, spiral clouds gradually form in the center of the cyclone, and the water vapor rising from the sea surface will further increase, forming a strong updraft, gradually developing into a tropical storm and finally forming a typhoon.

Source | Eumetrain

However, the formation of a typhoon is a relatively complex process, which is affected by many factors, including ocean temperature, wind shear, atmospheric humidity, etc.

Scientists can use meteorological satellites, meteorological radars and other means to study and predict the formation and path of typhoons, thereby providing reasonable guidance and warnings for people's production and life.

2Will there be thunder on typhoon days?

To answer this question correctly, we first need to understand the principle of thunder.

It is generally believed that thunderclouds are the result of strong, humid, hot air rising continuously into the thin upper atmosphere and condensing under favorable atmospheric and ground conditions, while thunder is a natural phenomenon caused by uneven distribution of electric charges in the atmosphere.

There are many small water droplets and ice crystals inside the cloud. Strong updrafts pass through the cloud, and the friction and collision of water droplets generate static electricity. Light water foam is negatively charged and is blown higher by the wind to form large negatively charged thunderclouds; large water droplets are positively charged and condense into rain or float in the cloud to form some local positively charged areas.

Actual measurements show that at altitudes of 5 km to 10 km, the clouds are mainly positively charged, while at altitudes of 1 km to 5 km , the clouds are mainly negatively charged .

Source | ScienceCitizen

During the discharge process, a strong electric field is formed between different thunderclouds or between thunderclouds and the earth. With the development and movement of thunderclouds, once the electric field strength in space exceeds the critical electric field strength of atmospheric ionizing discharge (critical electric field strength refers to the electric field reaching a certain intensity under certain conditions, the atomic nuclei in the material will undergo nuclear fission, thereby releasing electrons), the electric field strength in the atmosphere is about 30kV/cm, and when there are water droplets, it is about 10kV/cm, spark discharge will occur between clouds or to the ground , releasing tens or even hundreds of kiloamperes of current, generating strong light and heat, causing the surrounding high-temperature air to expand and vibrate rapidly, and thunder and roar occur, so the key to the generation of thunderstorm weather lies in the accumulation of electric charges.

Source | pixabay

Source | Zhitian Weather

During the formation and movement of a typhoon, the warm and humid air on the sea surface constantly converges from high-pressure areas to low-pressure areas, and the air rising in the high altitude is affected by the Coriolis force and radiates outward from the center. In this process, the wind speed of the typhoon is too fast (either vertically or horizontally), which makes it very easy for electric charges to be exchanged and difficult to accumulate , and it is impossible to form a voltage difference, so there is rarely a phenomenon of thunder . However, very few super typhoons are also accompanied by lightning.

Source | China Digital Science and Technology Museum

3. How to protect yourself during typhoons?

The arrival of typhoons is often accompanied by strong winds, heavy rains and storm surges, which affect a wide range of coastal and inland areas, seriously affecting people's daily lives and even threatening people's lives and property safety. Therefore, it is particularly important to master measures to deal with typhoon weather!

1. Avoid going out as much as possible and stock up on emergency supplies such as food and water in advance; ensure the safety of electrical circuits, gas and other facilities; use tape to form a "米" shape on the window glass to prevent the window glass from breaking.

Source | China Weather Network

2. Residents living in dilapidated houses should move to safe areas in a timely manner ; if they happen to be outdoors, they should stay away from temporary buildings, large trees, and billboards, and quickly take shelter in sturdy buildings.

Source | China Weather Network

3. Before a typhoon arrives, safety inspections must be carried out on fishery facilities to ensure that mechanical equipment can operate normally; emergency preparations must be made in advance to minimize the probability of dam and pond collapse; fishing boats out to sea should return to port as soon as possible and evacuate high-risk locations such as reservoirs and waterlogged areas.

4. Offshore workers should immediately evacuate to a sheltered place . If they cannot escape in time, they should promptly contact the relevant departments on shore through radio communication equipment. While waiting for rescue, they should take emergency measures, such as delaying navigation, detouring, and quickly passing through, to avoid being caught in the typhoon center or storm area.

If there is no radio communication equipment on board, you should pay attention to passing ships or aircraft and send out distress signals in a timely manner, such as stacking "SOS", emitting sound and light signals, shaking brightly colored objects, etc.

Source | China Weather Network

5. In order to reduce the impact of typhoon-induced flood disasters on agricultural production activities, first, dredge ditches to ensure smooth irrigation and drainage of field crops; second, inspect and reinforce production facilities , harvest mature crops in time, and organize the evacuation of field workers.

Source | China Weather Network