How heavy is the rain?

Torrential rain

/kloc-rain with rainfall greater than or equal to 1 6 mm per hour, or rain with rainfall greater than or equal to 50 mm within 24 hours.

I feel very honored. Today, I will systematically introduce the formation of rainstorm, the disasters caused by rainstorm, and how to monitor and forecast rainstorm, mainly introducing these contents. Rainstorm is a very important disaster in China, especially in the Yangtze River basin or the whole area south of Huaihe River. Of course, there was a big flood in the Yellow River. So generally speaking. Rainstorm is a major meteorological disaster in China. Understanding and studying rainstorm is an urgent task. At present, we mainly use radar and satellites to observe and predict the occurrence and development of heavy rain, but in the future, by 2025, the resolution of our numerical model will reach one kilometer. What is the concept of one kilometer? In this part of Beijing, we are only one kilometer from one place to another. As I said just now, what is the distance from one station to another? It's 200 to 300 kilometers. By 2025, I'm talking about a point-to-point observation distance of only one kilometer. In other words, what's the difference between this street and that one? I can work it out by computer. We can predict the next 30 days. What is the concept of one kilometer? It is equivalent to seeing the ground from this satellite. The terrain on this ground is so clear that it is called one kilometer. If you look at Beijing, you can basically see the street distribution in Beijing.

Therefore, in the next twenty years, the development of the whole meteorological cause and the level of meteorological science and technology will change greatly with the development of computer and electronics disciplines and the development of meteorological science itself in China. By that time, our forecast level and forecast accuracy within three days will never be lower than 90%. So from this perspective, I think our meteorological science has a brand-new concept, just like twenty or thirty years ago. I think my lecture is over, thank you!

Storm (full text)

I feel very honored to have the opportunity to introduce the rainstorm to you today. Today, I will systematically introduce the formation of rainstorm, the disasters caused by rainstorm, and how to monitor and forecast rainstorm, mainly introducing these contents. Rainstorm is a very important disaster in China, especially in the Yangtze River basin. Or the whole area south of Huaihe River in China. Of course, there was a big flood in the Yellow River. So in general, rainstorm is a major meteorological disaster in our country, so everyone is concerned that there was another flood in the Huaihe River Basin during the flood season in 2003, so this picture is a satellite cloud image released by Fengyun-2 meteorological satellite developed by our country, and we can see a cloud belt over the Huaihe River Basin for a long time.

So, for example, 1998, due to the flood in the Yangtze River basin, the whole country lost more than 300 billion RMB. /kloc-more than 0/000 people were killed in the flood. Therefore, flood disaster is different from drought. Flood disaster is like an acute disease, which will cause sudden losses to people's lives and property. Generally speaking, drought, like our chronic disease, affects for a long time. It will also cause great losses, but it is mainly the economy, especially agricultural production. So from this table, we can see that in recent years, our country as a whole has suffered more and more losses due to meteorological disasters. With the development of China's national economy, the losses caused by meteorological disasters also increase with the development of national economy. So this is obvious from above.

We are also a flood disaster. For example, on August 5, 2006, there was a tropical cyclone in Shanghai from 1 to 10, which caused a heavy rain and flooded the whole Shanghai. So a disaster like this, if everyone knew it twenty years ago, was that several quilts were wet. But today, every family has all kinds of household appliances, and soaking in water will cause great losses. The same is true in that factory. The equipment in the factory now can't be compared with the factory decades ago. Therefore, with the development of China's national economy, the losses caused by rainstorm disasters to China's entire economy are becoming more and more serious. So this picture is caused by the flood in the Huaihe River basin, and we can see the flood in the countryside.

So it is very important to forecast the rainstorm now, because we should take measures to prevent floods. 1998 floods are a great threat to the Three Gorges Reservoir, and it is very important to make a good rainstorm forecast to ensure the construction safety of the Three Gorges Reservoir. In this process, China Meteorological Bureau has played a great role in ensuring the Three Gorges Reservoir to survive the flood. We basically guaranteed the meteorological forecast and meteorological support for the entire Three Gorges Reservoir during the flood. For example, by the end of the flood, the Three Gorges Reservoir had been greatly affected by the earth dam, that is, the dam made of soil had been soaked in the water for a long time. If there is another rainstorm exceeding 50 mm, all the machinery and equipment of the Three Gorges Reservoir will be evacuated. Personnel should be evacuated to ensure the safety of mechanical equipment and personnel. Then at this time, the Yangtze Three Gorges Corporation asked the China Meteorological Bureau to give a correct forecast. Is it possible to have another rainstorm over 50 mm later? If there is going to be a rainstorm exceeding 50 mm, all these personnel and equipment should be evacuated from the Three Gorges site. Then the National Meteorological Center correctly predicted that the precipitation would not exceed 50 mm, so the whole project could not be stopped. If all equipment and personnel are evacuated from the Three Gorges Reservoir, it is estimated that the project progress will be delayed by one year. Therefore, meteorological support, especially rainstorm forecast and disaster forecast, has played a great role in safeguarding major projects in China. However, the rainstorm forecast is not a simple matter. There are two main difficulties in rainstorm forecasting. The first rainstorm was sudden and intense. As we all know, in summer, we see a large dark cloud rising from the west. It won't be long before it rains heavily. This is what we call a rainstorm. Especially in the rainy season, it often happens, so the sudden occurrence of heavy rain has a great influence on our forecast, and the area of heavy rain is usually relatively small.

For example, let me give you an example. On July 2 1, 1998, there was a three-day rainstorm in Wuhan, with an hourly rainfall of 88.4 mm. What is the equivalent of three days' rainfall in Wuhan? I wonder if the audience here have ever been to Wuhan? There is a place called East Lake in the center of Wuhan. The water falling in three days is equivalent to 1.5 times of the water inflow of East Lake, falling over Wuhan. Then this will definitely cause water disasters in Wuhan, so from this perspective, how to forecast this rainstorm is a very difficult place. Especially its turning point, critical moment, is particularly difficult. When did it happen? Where did it happen? How strong is it? This is a very difficult thing in our meteorology and weather forecast.

The second rainstorm forecast must have happened under the background of a certain atmospheric general circulation, which is the general motion state of our atmosphere. Especially those who care about the weather forecast will always hear the so-called tropical negative high. The negative tropical high is a high pressure belt that controls our southeast coast in summer, and this high pressure has a great influence on our whole eastward airflow. To the west of this negative tropical high, there must be a southbound airflow. Moreover, this southerly airflow brings a lot of warm and humid air from the south to the north, so the change of tropical negative high pressure can make our water vapor directly sent from South China to the Yangtze River basin. This caused the cold air from the north to come over and the warm and humid air from the south to go north. When cold and warm air collide, strong convection occurs. Warm air comes, cold air goes down and warm air goes up. In this way, the warm air goes up desperately, and it is warm and wet. So in the process of rising, it cools down and becomes precipitation, and then falls down. Therefore, the whole process is a very complicated problem in dynamics, physics and thermodynamics. So this rainstorm forecast is a very difficult place. Therefore, in order to make a good rainstorm forecast, we must first do a good job of monitoring. Therefore, if we can improve the ability of rainstorm forecasting, we will actually improve the overall ability of disaster prevention and mitigation in our whole country. So how do we monitor the rainstorm? This is a matter of great concern to us.

I think the following, as far as our current scientific and technological development is concerned, I will introduce it to you. Let me first talk about how the rainstorm is formed. Generally speaking, there are three kinds of rainstorm, one is the Meiyu front rainstorm I just mentioned. The second is a typhoon, or a typhoon with low intensity. We call it a tropical cyclone. Thirdly, in summer, we often encounter heavy rain brought by convection. So we generally divide rainstorm into three types. So how did the rainstorm form? It has three main conditions. The first condition, you must have enough water vapor to form a rainstorm. The second is that you have enough steam. How is this steam sent from bottom to top? So there must be upward movement. That is, this steam must climb up. As we all know, the temperature of the lower atmosphere is relatively high, and it becomes lower in the upper atmosphere. Then, as we all know, we never said that opening the window was for flying. Why? Because when the plane flies into the sky, it is tens of degrees below zero outside the glass window. So if the plane flies in the sky, it must be sealed. It must ensure that the inside of the plane reaches the temperature and humidity comfortable for our human body. So when our warm and humid air climbs up, it condenses into water drops as soon as it meets cold. If this water drop is greater than such a supporting force caused by our upward movement, then this water drop will fall, and then a rainstorm will be formed. Therefore, the second condition must have a strong upward movement. The third condition is stability. What is stability? I just said that if our warm air is below, our cold air is above. As we all know, the proportion of cold air is large, while the proportion of warm air is small. So warm air will definitely rise and cold air will come down. This will lead to agitation in the atmosphere, and the cold will drop and the warmth will rise. After this caused a somersault, it caused a strong upward movement, because warm air had to climb up and cold air had to come down to warm the air. As soon as this warm air goes up, it will cause what I just said, and it will condense when it meets cold. When it condenses, it becomes a water drop, and when it falls, it becomes rain.

Therefore, the formation of heavy rain must meet these three conditions: the first is rich water vapor. Since it is a rainstorm, it is a rainstorm. Then I said 2 1, 65438,998 It rained so heavily in Wuhan in July, 1.5 times the amount of water in East Lake fell from the air. Then you can imagine how big and rich the water vapor is. Second, it must have a strong upward movement. Then let's think about it. It lifted 1.5 times of East Lake water into the air in three days. Then imagine how powerful it is. Third, you should create the second condition. The atmosphere must be very unstable. Is the cold air desperately down, warm air desperately up. It will cause a lot of agitation, just like our water. As we all know, when the water is about to boil, bubbles in the water below will definitely come out. When the water boils, that is, when it reaches 100 degrees Celsius, the whole water bubble pops up. This is similar to the motion of the atmosphere. If it's hot down there, you must have hot air to run up. The air above is cold and the air below is hot. Hot air runs up desperately and cold air falls down desperately. So it's like boiling water in water. If you look closely at the boiling water, it is boiling desperately. The atmosphere is actually the same, so from this perspective, these three conditions are necessary.

The second typhoon, which is slightly weaker than a typhoon, is called a tropical cyclone. Then one of these two is a weak little brother and the other is a big brother. This gap is basically similar in structure. Now, from our satellite point of view, we can observe this typhoon very correctly. This is a typhoon seen from the satellite. We can see that this typhoon has a very strong spiral cloud belt. In other words, its airflow rolls from the outside to the inside, which is a typhoon. It's involved, so there is a typhoon eye in the middle. Blue is not a cloud, just a sunny day. Then there is a typhoon eye in the middle, so what does it look like? In fact, older comrades are very experienced. There used to be a water tank near our house. When I was a child, we all liked to take a bamboo pole and bang in this water tank. As soon as it is stirred, it turns, because the middle is empty and the water falls off. The water on both sides will stand up, just like a typhoon. Look at this. There is no water in the middle. It fell down. The water is right in front of us, and the typhoon is like this. So a typhoon is a strong vortex in the air, just like we stir a bamboo pole in a water tank. Of course, this does not mean that there is a god stirring there, but because of some atmospheric conditions, the whole atmosphere rotates there. It turns faster and faster, and finally it is like a stick stirring in a water tank. So the structure of this typhoon is like this, so our comrade who has a little past life experience will understand what a typhoon eye is when you talk to him. It rains everywhere else here. How can it be sunny here? That's the truth.

Then I will briefly talk about the third kind of rainstorm, which is caused by the thermal convection we saw in summer. That is to say, I am very hot today, and there will be a little cold air tomorrow. The very hot air on this ground will rise immediately, and then it will condense into heavy rain. Moreover, this kind of rainstorm has a short time and a small scope, which is completely incomparable with the Meiyu rainstorm I just said. So generally speaking, we have three kinds of heavy rain: one is Meiyu front. That is, when the seasons change, the south must have experienced this period from spring to summer. The second is the rainstorm caused by typhoon. The rainstorm caused by typhoon is the typhoon coming, and the rainstorm is coming. As soon as the typhoon left, the rainstorm left. The third kind, which we often encounter in Beijing, is the rainstorm caused by thermal convection, if it is longer than an hour or two, it is shorter than an hour.

Then I'll talk about how to monitor this rainstorm. How do you go to see the rainstorm? I'm just telling you a phenomenon, and I'll tell you why it caused such a heavy rain. Therefore, the monitoring equipment of this rainstorm is very different from that of twenty or thirty years ago. Young comrades present, he has never been there. Maybe older, maybe have been to the weather station. At that time, a weather station was a weather vane on a telephone pole, and then several louver boxes. This is a weather station. It's very different now. Now our meteorological equipment ranges from satellites and radars to computers. The routine monitoring in China is 124 radiosonde. The so-called radiosonde is a balloon, and an instrument for detecting air pressure, temperature and humidity is hung under the balloon. As soon as the balloon was released, the equipment went up. It measures air pressure, temperature and humidity, and then transmits them by radio. Then receiving this is called sounding, so this equipment can be said to be decades old. The second one I want to show is radar. Our previous general radar did not use the principle of Doppler radar, so I won't go into this. Previous radars could only see the echo of clouds. Because radar radio waves are emitted, they will be reflected as long as they touch water droplets in the cloud. Then you receive it, and this is the echo. Then there are water droplets in it, so the echo is strong. It means that the thicker the cloud, the bigger the water droplets. So in the past, ordinary radar could only detect this. What's the difference between Doppler radar and it? Thanks to the Doppler principle, I can also measure what the wind is like in the clouds. How strong is the updraft in the cloud? Is it the south wind or the north wind? Polarization radar and dual polarization radar will be developed in the future. I can not only measure how strong the wind is. I can also detect whether the cloud is ice or water. Or other substances? Therefore, compared with 20 or 30 years ago, the current means are completely incomparable. Today's radar, satellites and a series of other means provide us with sufficient weather forecast information.

Now I will focus on how satellites and Doppler radar monitor our rainstorm, that is, how to monitor it by modern means. Then we can monitor rainstorms, typhoons and other weather phenomena. I'll take this as an example now. This is all the satellites at present, and they generally follow this orbit. Meteorological satellites are generally divided into two categories: one is along the polar orbit, which we call polar orbit satellites. The other is a synchronous satellite, which is always in the same position. The reason is that its rotation speed is basically the same as our earth, so it has been motionless above our heads. Polar-orbiting satellites orbit around the polar regions, so there are two kinds of meteorological satellites. Then our country now has these two kinds of satellites. We now have one called Fengyun 1 and one called Fengyun 2. So Fengyun 1 is a polar-orbiting satellite and Fengyun-2 is a synchronous satellite. So what do we do now? Basically, we let these two kinds of satellites run overhead. This is what I'm talking about. This is Fengyun 1. This is Fengyun II in China, so it's basically like this.

This is the flow field calculated by observing a system with two or three Doppler radars at the same time. This was observed by radar. According to radar observation, this is a strong echo. This echo shows that this is a rain belt, and this is the wind field we observed with Doppler radar. Then we can see that such a fine structure can be observed by radar now. We can't see this subtle structure by conventional methods. What is the reason? The normal weather I just showed you, whether it is a sounding station or a radar station, what is its own distance? It's 200 to 300 kilometers. How big is our rainstorm? The usual range is about 100 km. As you can imagine, we are like catching fish. If our fishing net has a large mesh and this fish is small, let's think about it. Can I catch small fish with a large mesh fishing net? You'll never catch it. The small fish must have slipped through the net, and so did our observation. The rainstorm is only 100 km, and the distance between my weather stations is 200 to 300 km. How can I see it? I have a weather station here, there is a weather station here, this rainstorm system is smaller than it, and it leaks here. If I use two radars to observe at the same time, I can catch it. So why do we use two or three radars to observe at the same time? Because we can't see it through routine observation, we can only see it in this way.

So how will the rainstorm develop in the future? When the rainstorm comes in 2025, the horizontal resolution of our numerical model will be one kilometer. What is the concept of one kilometer? In this part of Beijing, the distance from one point to another is only one kilometer. As I said just now, what is the distance from one station to another? It's 200 to 300 kilometers. By 2025, the observation distance from one point to another is only one kilometer. That is to say, what is the difference between this street and that street? I can work it out by computer. After 20 years, we can reach this level. By then, how high will the resolution of our geosynchronous satellite be? It can provide images with a resolution of 500 meters in just 30 seconds. At that time, our radar could realize dual polarization radar. I can not only see the wind, but also see whether the cloud is ice or water and at what height. At that time, we had low-orbit satellites, through which we could give the global wind field. How to get the wind field above the sea surface? Not observed at sea. Now we can give all the wind fields in the world through low-orbit satellites. We can use space satellites to observe thunderstorms. Where does the thunderstorm happen? The accuracy can reach 100 meter. By then, we can see the fine three-dimensional wind field structure in the whole atmosphere through other equipment. We can predict the next 30 days. Therefore, in the next twenty years, the development of the whole meteorological cause and the level of meteorological science and technology will change greatly with the development of computer and electronics disciplines and the development of meteorological science itself in China. By that time, our forecast level and forecast accuracy within three days will never be lower than 90%. So from this perspective, I think our meteorological science has a brand-new concept, just like twenty or thirty years ago.