torrential rain(English name torrential rain; rainstorm; Storm) refers to rain with high precipitation intensity, which is often formed in cumulonimbus clouds. According to the meteorological regulations in China, rain with an hourly rainfall of more than 16mm, or a continuous rainfall of more than 30mm for 12 hours and a 24-hour rainfall of 50 mm or more is called "rainstorm".
According to its precipitation intensity, it is divided into three grades, that is, the 24-hour precipitation is 50-99.9 mm, which is called "rainstorm", the 100-249.9 mm is called "heavy rainstorm" and the 250 mm is called "extraordinary rainstorm". However, due to the different characteristics of precipitation and topography, the standards of rainstorm and flood in different places are also different.
In business practice, rainstorm can be divided into local rainstorm, regional rainstorm, large-scale rainstorm and extra-large rainstorm according to the scope of occurrence and influence.
The local rainstorm lasts only a few hours or dozens of hours, and generally affects tens to thousands of square kilometers, causing less harm. However, when the rainfall intensity is extremely high, it can also cause serious casualties and property losses.
Regional rainstorm generally lasts for 3 ~ 7 days, and the influence range can reach 100 ~ 200,000 square kilometers or more. The disaster situation is average, but sometimes it may cause serious regional rainstorm and flood disaster due to the extremely strong rainfall intensity.
Extra-large-scale rainstorm lasts the longest, and it is generally a combination of continuous rainstorms in many areas. The rainfall can last intermittently for about 1 ~ 3 months, and the rain belt can be maintained for a long time. Torrential rain is a kind of disastrous weather, which often causes floods and serious soil erosion, leading to major economic losses such as engineering accidents, dike breaches and crop flooding. Especially for some low-lying and closed terrain areas, rainwater can not be quickly vented, resulting in farmland water accumulation and soil moisture over-saturation, which will cause more disasters.
How to observe weather signs and avoid heavy rain?
In summer, when observing the following weather signs, we should strengthen our vigilance against the occurrence of heavy rain.
1. It is sultry in the morning, and even it is difficult to breathe. It is generally a sign that the low-pressure weather system is approaching, and there is often heavy rainfall in the afternoon.
2. In the morning, I saw a pagoda-shaped ink cloud uplift in the distance, and generally there will be a strong thunderstorm in the afternoon.
3. The weather was clear and cloudless for many days, and it was particularly hot. Suddenly, I saw a small cloud group rising on the windward slope of the mountain, and there was usually a strong thunderstorm at midnight or early morning.
4. On a hot night, hearing a dull thunder not far away is generally a sign that a rainstorm is coming.
5. When you see a funnel-shaped cloud or a dragon’s tail cloud on the horizon, it indicates that the weather is extremely unstable, and thunderstorms and strong winds may come at any time.
How to defend against heavy rain or rainstorm?
If it rains heavily, you can defend yourself from the following aspects.
1. In low-lying residential areas, measures of "small enclosure" can be taken according to local conditions, such as building a fence, placing a water baffle at the gate, and configuring a small water pump.
2. Don’t throw garbage, sundries, etc. into the sewer, in case of blockage, resulting in water accumulation during rainstorm.
3. Electrical sockets, switches, etc. in the homes of residents at the bottom should be moved to a safe place more than 1 meter from the ground. Once the outdoor water overflows into the house, the power supply should be cut off in time to prevent electric shock from hurting people.
4. Pay attention to observation when walking in stagnant water. Prevent falling into manhole or pit or hole.
5. The river is an important drainage channel in the city, and it is not allowed to dump garbage and waste at will to prevent siltation.
How to avoid heavy rain, mountain torrents and mudslides?
The arrival of the typhoon, in addition to direct storms, often brings many secondary and derivative disasters. It is easy to induce geological disasters such as mountain torrents and mudslides in mountainous areas. This website has collected some popular science knowledge about mountain torrents and mudslides, please refer to it.
Who are vulnerable to the threat of mountain torrents?
According to the analysis of the data of mountain flood disasters over the years, there are often the following groups of people who are vulnerable to the threat of mountain flood disasters:
(1) Do not know the rainstorm warning information and flash flood outbreak information, or fail to predict the intensity of the rainstorm, and engage in activities on the high mountains or under steep slopes and on both sides of streams and rivers in flash flood-prone areas without authorization; Or in case of continuous heavy rain, people who rest in their houses at night and are unprepared are vulnerable to the threat of flash floods.
(2) During the period of flash floods and flood surges, people who are in a hurry to go out and cross the river, bridge or transition at will. Even wood and furniture floating in the creek are desperate, standing by the river where the flood is soaring to salvage, or taking temporary bamboo rafts, wooden rafts, wooden barrels and ships to rescue property and waterlogging floating objects, which is most likely to be dangerous.
(3) People who randomly build houses and live in the open space at both ends of Xihe Bridge, without considering the flash floods, often carry a lot of sand, stones and firewood trees, which are easily blocked when passing through the arch culvert of the bridge, leading to the flood surge, which is easy to cause the bridge or the bridge head to be washed away, thus causing harm to people and property.
(4) Residents who build houses without protection by cutting slopes or build their houses at the foot of steep slopes are vulnerable to the threat of mountain torrents. Homestead selection lacks awareness of flood control, and residents in the lower places on both sides of the stream, at the intersection of the two estuaries and at the bend of the river are vulnerable to the threat of flash floods.
(5) Residents who build houses on the hillside with deep residual slope accumulation or the cracked and easy-to-collapse and easy-to-slide hillside in the flash flood prone area may collapse and slide in case of erosion and erosion by torrential rain, and their lives and property will be threatened.
How to avoid mountain torrents and mudslides?
(1) When it is known that debris flow will occur in a certain area for a period of time, emergency evacuation and protection measures should be taken in this area, and personnel should be forcibly moved to a safe area.
(2) Don’t run upstream or downstream along the debris flow ditch, but run to the slopes on both sides of the ditch bank, and don’t stay at the concave slope.
(3) Establish temporary shelter. The shelter should be located to avoid concave banks of ditches, small and flat convex banks and steep slopes, and should be placed on low and gentle slopes or high terraces near the village.
How to get out of danger quickly when encountering mountain torrents in the early hours of the night?
According to the historical lessons of sudden flash floods and mudslides in the early hours of the night, there are the following tips.
All residents who live in mountain torrents-prone areas or gullies, canyons and streams must keep a high degree of vigilance whenever there is continuous heavy rain, especially at night. If there is any abnormality, they should immediately organize personnel to leave the scene quickly, choose a safe place nearby, and try to contact the outside world to do the next rescue work. Never take chances or save property and delay the opportunity to avoid disasters, causing undue casualties.
Experts from China Meteorological Bureau explain in detail what the public should do after the rainstorm warning is issued.
Author: Liu Yi
What should you do after the rainstorm warning is issued?
Experts from China Meteorological Bureau explain the matters needing attention in detail.
Interpreter: Zhang Jianzhong, Senior Engineer of National Meteorological Center of China Meteorological Bureau.
On July 31, the Central Meteorological Observatory continued to issue a blue rainstorm warning.
How is the rainstorm warning graded? What should the public pay attention to under different levels of early warning? On July 31st, the reporter interviewed experts such as Zhang Jianzhong, senior engineer of National Meteorological Center of China Meteorological Bureau.
Blue warning-when the rainstorm comes, it is best to stay indoors and stay away from the window; Don’t take shelter from the rain under big trees outdoors, don’t hold metal objects and pick up mobile phones to prevent lightning strikes.
Zhang Jianzhong introduced that the Central Meteorological Observatory issued a blue, yellow, orange and red warning for heavy rain. Its severity increases from low to high.
The standard of blue rainstorm warning by the Central Meteorological Observatory is: it is estimated that there will be more than 50 mm rainfall in most areas of two or more provinces (autonomous regions and municipalities) in the next 24 hours, and there will be patches of rainfall in the south or scattered rainfall over 100 mm in the north.
What should the public pay attention to in the area covered by the blue rainstorm warning? Zhang Jianzhong warned that when the rainstorm comes, it is best to stay indoors and away from the windows. Stay in the house and always pay attention to gas leakage, turn off gas and circuits, and leave the house quickly if you see flames. If it thunders, don’t watch TV or surf the Internet, but unplug the power supply, telephone line and TV antenna and other metal wires that may introduce lightning strikes. In addition, don’t use solar water heaters to take a bath in thunderstorm weather.
When you are outdoors, you should enter the room as quickly as possible. If you have no time to hide, you should use what you can find to protect your head from injury. Due to the short circuit of wires in heavy rain, people may be electrocuted and die, so they should stay away from wires. Don’t take shelter from the rain under big trees, don’t hold metal objects and pick up mobile phones to prevent lightning strikes, stay away from rivers, lakes, rice fields and open areas, and stay away from billboards and simple buildings.
Yellow warning-try to avoid vehicles driving in stagnant water; Check the drainage system of cities, farmland and fish ponds and take necessary drainage measures.
The criteria for the yellow rainstorm warning of the Central Meteorological Observatory are: rainfall of more than 100 mm occurred in most areas of two or more provinces (autonomous regions and municipalities) in the past 24 hours, and it is expected that rainfall of more than 50 mm will still occur in the above areas in the next 24 hours; Or it is predicted that in the next 24 hours, there will be more than 100 mm rainfall in most areas of two or more provinces (autonomous regions and municipalities), and there will be patches in the south or scattered rainfall over 250 mm in the north.
Zhang Jianzhong said that after the yellow rainstorm warning is issued, the traffic management department should take traffic control measures in heavy rainfall sections according to the road conditions, and implement traffic guidance in stagnant water sections. When the accumulated water depth exceeds the exhaust pipe, road closure measures should be taken; After the culvert of the overpass has accumulated water, the relevant government departments should immediately block the overpass and set up warning signs; In low-lying sections with large areas of accumulated water, relevant departments should clear the drain in time.
It is best for the public not to ride bicycles or drive when it rains heavily, and try to avoid vehicles driving in stagnant water. After the rainstorm comes, immediately drive the car to a higher ground and park it. Never park it in a low-lying place. Cut off the dangerous outdoor power supply in low-lying areas, suspend outdoor work in open places, and transfer people in dangerous areas and residents in dangerous houses to safe places for shelter from the rain; Pay special attention to the rainstorm at night, and beware of the collapse of dilapidated and damaged houses. Check the drainage system of cities, farmland and fish ponds and take necessary drainage measures.
Orange warning and red warning-rainstorm may have caused or will soon lead to disasters such as rising water levels in rivers and lakes, ground traffic disruption and power transmission line disruption; You should immediately find a safe building to avoid and wait for the rain to stop.
The criteria for the orange rainstorm warning of the Central Meteorological Observatory are: in the past 48 hours, rainfall with a daily rainfall of more than 100 mm has continued in most areas of two or more provinces (autonomous regions and municipalities), and there are patches of rainfall with a daily rainfall of more than 250 mm in the southern region or scattered rainfall with a daily rainfall of more than 250 mm in the northern region. It is expected that there will still be rainfall of more than 50 mm in the above areas in the next 24 hours; Or it is predicted that there will be more than 250 mm rainfall in most areas of two or more provinces (autonomous regions and municipalities) in the next 24 hours.
The criteria for the red rainstorm warning of the Central Meteorological Observatory are: in the past 48 hours, most areas of two or more provinces (autonomous regions and municipalities) have continuously experienced rainfall with a daily rainfall of more than 100 mm, and the above areas have rainfall with a daily rainfall of more than 250 mm. It is expected that there will still be rainfall of more than 100 mm in the above areas in the next 24 hours.
Zhang Jianzhong pointed out that after the orange or red rainstorm warning issued by the Central Meteorological Observatory, the rainstorm may have caused or will soon lead to disasters such as rising water levels in rivers and lakes, ground traffic disruption and power transmission line disruption. All relevant departments should immediately enter the emergency post, closely monitor and take rescue measures; People near mountains, hills and rivers should be evacuated to safe areas immediately; Organizers of large-scale mass activities should immediately stop their activities and properly arrange or try to evacuate people safely; Hospitals, schools and other units should resolutely take measures to ensure the safety of their own personnel and stop going out; People should immediately look for safe buildings to avoid. Drivers should observe the surface runoff when their vehicles are turned off or unable to run normally. If the runoff is rapidly gathering, they should resolutely abandon their vehicles and wait for the rain to stop before moving their vehicles. All units and personnel in the early warning area should listen to and watch the emergency information and meteorological early warning information of relevant departments in time.
Meteorological departments at or below the provincial level issued four warning signals of blue, yellow, orange and red, with specific standards and defense guidelines.
Zhang Jianzhong introduced that the Central Meteorological Observatory issued a blue, yellow, orange and red warning for the rainstorm, but did not issue an early warning signal. The meteorological departments at the provincial level and below issued a blue, yellow, orange and red warning signal. These four-level warning signals have their own specific standards and defense guidelines.
The standard of blue rainstorm warning signal is that the rainfall will reach more than 50 mm within 12 hours, or it has reached more than 50 mm and the rainfall may continue.
Yellow rainstorm warning signal’s standard is that the rainfall will reach more than 50 mm within 6 hours, or it has reached more than 50 mm and the rainfall may continue.
The standard of rainstorm orange warning signal is that the rainfall will reach more than 50 mm within 3 hours, or it has reached more than 50 mm and the rainfall may continue.
The standard of rainstorm red warning signal is: within 3 hours, the rainfall will reach more than 100mm, or it has reached more than 100mm and the rainfall may continue.
Zhang Jianzhong said that the meteorological department has formulated different defense guidelines for early warning signals of blue, yellow, orange and red. Taking the common blue warning signal of rainstorm as an example, after the blue warning is issued, the government and relevant departments should make preparations for preventing rainstorm according to their duties; Schools and kindergartens take appropriate measures to ensure the safety of students and children; Drivers should pay attention to road water and traffic jams to ensure safety; Check the drainage system of cities, farmland and fish ponds, and make good preparations for drainage; The public should enter the safe building as soon as possible.
(Editor: Liu Jie)
