2012 July 2 1 day, Beijing was hit by a rainstorm. This rainfall is the biggest in 6 1 year. The meteorological department has issued an orange rainstorm warning. The average precipitation of this heavy rainfall reached 170 mm, and the maximum rainfall point was 460mm in Hebei Town, Fangshan District. The rainstorm flooded Beijing and sounded the alarm for other cities. I was very curious about this and launched an investigation. I checked the information on the Internet, and it turns out that storms and floods are divided into different types according to the causes of rainstorms. Heavy rain is a heavy rain with a precipitation of more than 50 mm within 24 hours. Rainstorm 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 blocked areas, rainwater can't be discharged quickly, which leads to water accumulation in farmland and supersaturation of soil moisture, which will lead to more geological disasters. Rainstorms often fall from cumulonimbus clouds. The condition for the formation of cumulonimbus clouds is that the atmosphere contains enough water vapor, and there is a strong upward movement to transport the water vapor rapidly upward. The water droplets in the cloud are constantly affected by the upward movement until the upward airflow can't support them, and they drop sharply to the ground. The characteristics of rainstorm and flood are mainly determined by rainstorm and restricted by the underlying surface conditions of the basin. In addition to the genetic types of rainstorm, there are also factors that affect the characteristics of rainstorm and flood: the location of rainstorm center, whether rainstorm center moves, the moving path, the area distribution and time-history distribution characteristics of rainstorm. Therefore, even the rainstorm with the same genetic type can cause floods with different sizes and peak shapes in the same basin. In the same basin, rainstorm and flood often have great interannual variation, and the magnitude of perennial flood and occasional rainstorm is very different, and the characteristics of flood process are not completely consistent. Rainstorm and flood have always been the most important content in applied hydrology. According to the characteristics of rainstorm and flood, hydrologists in various countries have established many calculation formulas and models. However, due to the randomness of rainstorm changes and the unstable and uncertain factors of basin underlying surface conditions, all physical mechanisms of rainstorm and flood formation have not been fully understood, and it is difficult to establish a very strict mathematical model. In practice, some generalized assumptions are often used to simplify the description of actual natural phenomena, and on this basis, reasoning analysis is carried out, and conceptual theories and methods are established to simulate this process (see watershed hydrological mathematical model). At the same time, due to the characteristics of rainstorm and flood, the application of mathematical statistics theory in rainstorm and flood analysis and calculation is often difficult. In 1930s, the United States put forward a hydrometeorological method to estimate the possible maximum rainstorm to calculate the possible maximum flood, which is another method in the study of rainstorm and flood. It is easy to cause floods, resulting in villages, houses, ships, bridges, amusement facilities and so on. Be flooded or even washed away, resulting in loss of life and property. May cause accidents in water conservancy projects. It is easy to cause geological disasters such as landslides and mudslides, causing casualties. Flood disaster: the flood exceeds a certain limit, which brings losses and disasters to human normal life and production activities. Flash flood refers to the sudden, rapid and violent surface runoff caused by rainfall in small watersheds in hilly areas, which has the characteristics of short duration, fast flow rate, strong scouring power and great destructive power. It will also cause traffic jams. There are all kinds of rain in nature, such as gray rain, continuous rain and rainstorm in Mao Mao. In an area, if there is a rainstorm in a short time, the river will rise very fast, and it will easily overflow dams, flood farmland and villages, destroy roads and houses, and make many people homeless. This is a flood disaster caused by heavy rain. Heavy rain refers to the rain with very heavy rainfall. So how to measure rainfall? Meteorologists placed a metal cylinder with a diameter of 20 cm in the open air at the ground observation site-rain gauge. The rainfall it receives 24 hours a day is the daily precipitation, which can be measured by a cup. Central weather bureau stipulates: drop every day.
Rainfall below 10mm is called light rain,10-25mm is moderate rain, 25-50mm is heavy rain, and above 50mm is called rainstorm. Rainstorm weather is dangerous to some extent, but not terrible. As long as all kinds of preventive work are done well, there will be no danger.
1. When the flood comes, take refuge according to the predetermined route, pay attention to helping the old and the young, and help each other. If the flood comes too fast to be transferred on foot, it is necessary to use boats or floating objects such as door panels and wooden beds prepared in advance as tools to transfer water.
2. When the flood comes quickly and the flood has entered the house, you should quickly climb the roof, wall or nearby trees, take refuge temporarily and wait for the ambulance personnel to move. You can't swim alone.
3. Earth walls, dry houses or mud brick houses can only be used as temporary shelters, because they are in danger of collapse at any time after being soaked in water.
If there are no big trees and courtyard walls, the roof will not climb up for a while. At this time, it is necessary to grasp the fixture and call for help from others.
After the flood, how to prevent the epidemic of diseases?
1? Remove stagnant water and dirt, ventilate and dry, spray disinfectant to prevent infectious diseases and mosquitoes and flies.
2. Take preventive drugs to avoid infectious diseases. If there is an infectious case, it must be treated in isolation.
3. Household appliances should be cleaned and disinfected, and damp and moldy items should be ventilated.
If it rains heavily in the mountainous area, flash floods will occur within half an hour. Mountain torrents come quickly, with high velocity, strong scouring ability and great destructive power, which will cause serious disasters to mountainous areas.
1. In case of flash floods, the teacher will escort you across the river. When the water depth exceeds the knee, singles cannot cross the river; When the water reaches waist-deep depth, people should never cross the river. If an accident happens and the river washes you down, you should be clear-headed and try to catch the floating objects in the river or the roots and branches on the shore to escape.
2. When the mountain torrents are rising so fast that the teacher can't escort them across the river, all the students have to go back to school for the night.
3. During the summer vacation, mow the grass and hoe the ground on the mountain, and take refuge in caves and other places when it rains cats and dogs, so as to prevent landslides, rolling stones and collapses.
In thunderstorm weather, the water in the valley rises rapidly, so students should move to high places, but they can't stay under big trees or run to the top of the mountain to avoid being hurt by lightning.
5. If the wires droop, you can't touch them with your hands or body; When the low power line has been washed away by the river, you can't stay by the river, let alone cross the river here. Electric shock accidents will occur in these situations, endangering life safety.
6. When the water depth is less than one meter, the fluctuation of water potential is not obvious, and primary school students have to cross the river in a hurry, the teacher can organize the following measures: tie everyone's waist into a straight line with long ropes, schoolbag belts and kettle belts, tighten their hands, and cross the river obliquely in the same direction as the water flow to reduce the water flow resistance.
Through this exploration, I feel that the rainstorm is actually not terrible, mainly because you will reduce the damage caused by the rainstorm.