What are the forms of rainfall?
The phenomenon of precipitation caused by typhoon activity is called typhoon rainstorm. Typhoon will not only bring strong winds, but also bring precipitation. The typhoon cloud system has certain rules, and the precipitation distribution in typhoons is also very regular. But after the typhoon landed, it was not so regular because of terrain friction. For example, there is precipitation in the whole vortex area with updraft in the wind, but the precipitation in the cloud wall area with the strongest updraft is the largest, and the precipitation in the spiral cloud belt is reduced, sometimes causing heavy rain, and the airflow in the typhoon eye area sinks, so there is generally no precipitation.
The typhoon area is full of water vapor, with strong upward movement and frequent heavy precipitation. When the typhoon comes, the average daily precipitation is above 800 mm, which is very strong and mostly sudden. When typhoons land, they often produce heavy rain, with rainfall ranging from 200 to 300mm to1000mm. In Xinliao, Taiwan Province Province, China, on June1967+065438+1October 17, due to typhoon 672 1 7.
frontal rain
When the front is active, the precipitation caused by the rising, cooling and condensation of warm and humid air is called frontal rain. Frontal rain is often accompanied by cyclones, so it is also called cyclone rain. There are systematic cloud systems on the front, but not every cloud can produce precipitation, which is explained as follows:
Frontal rain mainly occurs in the rain layer, and nimbostratus is the thickest in nimbostratus. It is also a mixed cloud formed by cold and warm air. Its upper part is ice crystals, the lower part is water droplets, and the middle part is often filled with ice water, which can quickly cause collisions. Because of the thickness of the cloud, the cloud droplets travel a long distance in the collision process, which is beneficial to the increase of cloud droplets. The bottom of nimbostratus is close to the ground, so raindrops are not easy to evaporate during the descent. The thicker the rain layer, the closer the cloud bottom is to the ground, and the stronger the precipitation.
High-level clouds can also produce precipitation, but generally it doesn't rain in cirrostratus. Because the cloud body in cirrostratus is thin, the cloud bottom is far from the ground, and the water content is low, even if raindrops fall, it is not easy to reach the ground.
Frontal precipitation is characterized by a large horizontal range, which often forms a large-scale banded precipitation area along the front, called precipitation zone. With the seasonal movement of the average position of the front, the position of the precipitation belt also moves. For example, in China, from winter to summer, the location of the precipitation belt gradually moves northward, in South China in May, to the Nanling-Wuyishan line in early June, to the Yangtze River line in late June, to the Huaihe River in July and to North China in August; From summer to winter, it moves south, starts to withdraw from northeast and north China in late August, and reaches the south China coast in September, so it moves south much faster than it moves north.
Another feature of frontal precipitation is that it lasts for a long time, because the rising speed of layered clouds is small, and the water content and precipitation intensity are relatively small. There is little precipitation in some pure water clouds. If there is precipitation, it is also Mao Mao rain. However, frontal precipitation lasts for a long time, ranging from a few days to more than ten days and a half months, sometimes for more than a month. "Rain after rain in Qingming Festival" is an accurate and appropriate description of frontal precipitation in Jiangnan area of China.
orographic rain
The phenomenon of precipitation caused by the forced uplift of airflow along the hillside is called topographic precipitation. Topographic precipitation often occurs on windward slopes. When warm and humid air flows over the mountains, if the atmosphere is unstable, it can also produce convection and form cumulus clouds; If the upward movement of airflow on the mountain is combined with the thermal convection in front of the hillside, cumulonimbus will develop into cumulonimbus and form convective precipitation.
In the process of frontal movement, if the forward direction is blocked by mountains, the frontal movement speed will slow down, the precipitation area will expand, the precipitation intensity will increase and the precipitation time will be prolonged, resulting in continuous rainy weather, which can last for more than 10~ 15 days.
In the world, the wettest place often appears on the windward slope of the mountain, which is called rain slope; The leeward slope has less precipitation and becomes a dry slope or "rain shadow" area. For example, the mountain slope in Scandinavia, Norway is windward, and the precipitation 1000 ~ 2000mm, while the leeward slope is only 300mm. For another example, the northern, eastern and southern slopes of the mountains in Taiwan Province Province, China are windward, with a lot of precipitation. The annual rainfall is more than 2,000 mm, and the fire in Taipei reaches 8,408 mm, which is the place with the most rainfall in China. As soon as it reaches the west, it becomes a rain shadow area, and the precipitation decreases to about1000 mm. Kauai Island in Hawaii has the largest annual rainfall in the world, with the windward slope of12040 mm. The annual precipitation in Kilapanchi, India is 1 14 18mm, which is also because it is located at the southern foot of the Himalayas.
convectional rain
Precipitation caused by atmospheric convection is also called convective rain. When the air near the surface layer is heated or the upper layer is strongly cooled, the lower layer air rises, and the water vapor cools and condenses, which will form convective rain, which is usually produced in cumulus clouds. There is usually a strong wind before the convective rain comes. Strong winds can pull up trees with a diameter of 50 cm, accompanied by lightning and thunder, and sometimes hail.
Convective rain mainly occurs in cumulonimbus clouds, where ice crystals and water droplets exist. The vertical thickness and water vapor content of the cloud are particularly large, and the airflow rises and falls very strongly, which can reach 20 ~ 30m/s. The cloud is charged. Therefore, cumulonimbus clouds often develop into strong convective weather, leading to heavy rain and lightning strikes. Strong winds and heavy rains often appear in this thunderstorm.
Pale cumulus clouds are very thin, with little water content, and generally no rain falls to the ground. Cumulus seldom rains in the middle and high latitudes, but in the low latitudes, it can sometimes produce precipitation because of its rich water content and strong convection.
Convective rainfall is the most frequent in low latitudes, and the precipitation time is generally in the afternoon, especially in equatorial regions, and the precipitation time is very accurate. In the morning, the sky is clear. With the rising of the sun, the sky cumulonimbus clouds gradually formed and developed rapidly, and became thicker and thicker. In the afternoon, cumulonimbus clouds surged, the weather was sultry, the wind passed, the thunder and lightning were mixed, and the rain poured down. The precipitation continued until dusk, and it was sunny and slightly cool after the rain, but the next day, there were repeated thunderstorms. In Bogor, Indonesia, there are thunderstorms 320 days a year. In the middle and high latitudes, convective rain mainly appears in the summer half year and is extremely rare in the winter half year.