East China Sea CycloneRefers to the frontal cyclones generated and developed in the East China Sea.Some are caused byJianghuai cycloneBodong moved into the sea and deepened.It has a great impact on the weather in the East China Sea, the eastern coast, Taiwan, Korea and Japan, often resulting in strong winds and precipitation in these areas.
Chinese name
East China Sea Cyclone
Foreign name
East China Sea cyclone
Scope of influence
East China Sea and its eastern coast, Korea, Japan
In a broad sense, the East China Sea cyclone is defined as "all the gases generated in the East China Sea are called East China Sea cyclones".Can'tJianghuai River Basineven to the extent thatYellow River BasinThe generated cyclones entering the East China Sea are also called East China Sea cyclones, otherwise they will cause confusion in the classification of cyclone source areas.Especially for the research work of forecasting methods, it is bound to affect the confusion in the classification of forecasting models.
Cyclones in the East China Sea are those that occur off the coast of China. Most of them develop in Japan (Japan called them "Taiwan masters" in the early days), and only a few develop in the East China Sea. Therefore, they often appear in the form of cyclonic waves on weather maps, but their peripheral pressure fields are often inverted troughs with different strengths.The occurrence and development of cyclones in the East China Sea have a great impact on the rainstorm and gale along the southeast coast of China.Although coastal stations have made many synoptic analyses and studies on cyclones in the East China Sea, most of their contents focus on solving forecasting problems, and little research has been done on the causes of their occurrence and development.With the development of fishery production, oil development and shipping, it is urgent to improve the ability of forecasting cyclones in the East China Sea. Especially in winter, the development of cyclones in the East China Sea often affects the safety of fishery production and shipping.
Research overview
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China's research on cyclones in the East China Sea can be roughly divided into three stages: the first stage (1950s): during this period, the more representative works are "On the generation and development of cyclones in the East China Sea" and "Analysis of two examples of the generation and development of low pressure in the East China Sea".The synoptic situation of the occurrence and development of cyclones in the East China Sea and the characteristics of meteorological elements are mainly put forward from the synoptic point of view.For example, on the surface weather map, when the Jiangnan rain belt moves eastward, the wind direction of Miyagi Shiyuan Island turns clockwise, and the △ P of Okinawa in the four countries shows a large negative value, then there will be cyclones in the next 12h-24h.The article also points out that on the 700mb map at high altitude, there is often a trough moving eastward in southwest China. If the trough line is in north-south direction, it is conducive to the development of cyclones, and if it is in east-west direction, it is not conducive to the development of cyclones.These arguments are still valid.Later, after the introduction of the advection dynamic theory of the Soviet Union into China, the advection dynamic theory was used to predict the occurrence of cyclones in the East China Sea, and it was pointed out that the dynamic decline in front of the trough was a necessary condition for the occurrence of cyclones in the East China Sea.If there is a high altitude pine with a cold advection degree in the north stronger than that in the south, local frontogenesis will occur, while the warm advection degree in front of the trough is stronger in the north than that in the south, which will cause local front extinction. In this case, the flow from local frontogenesis to local front energy dissipation will cause the surface gas generating cyclones in the dynamic depressurization area. If the local frontogenesis behind the trough is more southerly and the local front energy dissipation in front of the trough is more northerly,At this time, the cyclone is easier to develop.The later vorticity theory also pointed out the frontogenesis conditions for the occurrence and development of cyclones, and the conclusion that the upper level divergence caused the ground dynamic pressure drop, leading to the growth of cyclones.On the other hand, in summing up the experience of the generation and development of cyclones in the East China Sea trough, some people put forward that the temperature difference (i.e., the sea front zone) in the East China Sea caused by the intersection of the Kuroshio Warm Current from the Ryukyu Islands and the Cold Current from the Sea of Japan often occurred during the winter half year, which is the view that the East China Sea cyclones had good underlying conditions when they were generated early after the liberation of China.Using the entrance and exit area of the upper center of the jet stream, the position of the cyclone development in the East China Sea is calculated. It is found that the cyclone is located in the third quadrant, that is, the left front of the jet stream center, which is the most easily developed fact.Although there are few data, it shows that the upper jet sometimes plays an important role in the development of cyclones in the East China Sea.In the 1950s, various causes and theoretical problems concerning the occurrence and development of cyclones in the East China Sea have been put forward. It is reasonable that since 1958, the understanding of cyclones in the East China Sea should have a relatively mature stage of development and application in forecasting. However, due to various reasons, progress in this regard has been slow.
The second stage (1960s): since the 1960s, with the strengthening of weather forecasting in economic construction services, many forecasting methods for cyclones and gales in the East China Sea have been summarized, such as "gales along the coast of Zhejiang in winter" and other articles, which put forward many specific forecasting experiences for the occurrence and development of low pressure, which is still available for forecasters to grasp the law of situation evolution,It can be summarized as follows:
1. The distribution dynamics of △ P should be used as an indicator. For example, when there is positive △ P in the northwest area and negative △ P in the south of the Yangtze River, the central area is conducive to the development of low pressure.Another example is that the southwest region is negative △ P, if the center strengthens in the process of moving eastward, or weakens first and then strengthens, the latter is conducive to the development of cyclones.These are still available.
2. Using the dynamic of the rain area as an indicator, the Jiangnan rain belt is northeast southwest and extends northward, or the rain area on the East Sea develops northward, which is conducive to the formation and development of low pressure. In addition, the strengthening of the rainfall center in the process of moving eastward is also a sign of the development of cyclones.
3. Use 70omb situation to find indicators to divide circulation patterns.For example, if there are obvious cyclones in front of the trough, the industry will diverge downstream, which is conducive to the development of low pressure.The 700mb circulation and the occurrence and development of cyclones can be divided into four modes: A Siberian low trough, B east ridge east trough, C west ridge east silent, D transverse trough.
The third stage (1970s): during this period, the research on the causes of cyclones in the East China Sea began to deepen.It is found that the combination of the southwest airflow and the Kuroshio Warm Current can be conducive to the formation of the East China Sea trough, and whenever the high-altitude trough moves eastward, it will lead to the development of cyclones in the East China Sea.This has broken the habit of using 700mb upper frontal zone conditions for forecasting the occurrence of East China Sea cyclones in the past.In other aspects, through the reform of forecasting methods, the past index experience has been summarized, so that the model plus index method has been popularized and applied. At the same time, the modelStatistical forecastThe method has also achieved good prediction effect, but there is no new breakthrough in the research of cyclone gale prediction in the East China Sea, so the prediction effect is not much better than the practical effect of previous prediction methods.In general, although China has not done much research on cyclones in the East China Sea since liberation, the theory proposed is within the scope of the existing domestic and foreign literature.The problem is that there are great differences in the application of forecasting technology, especially in jet flow conditions and sea surface frontogenesis conditions, which affect the improvement of forecasting level.[1]
Simulation study
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Weather Facts
On June 1, 2006, due to the explosive development of the East China Sea cyclone, heavy rain or torrential rain fell in Zhoushanautomatic weather stationThere are 9 stations with measured precipitation of more than 60mm, among which Putuo Automatic Station has the largest precipitation of 100.5mm.From the morning of June 1, the coastal wind force in Zhoushan gradually increased. By the morning of June 2, the automatic weather stations and wind measuring stations in the city generally measured the 9-11 east to northeast gales. The four stations that reached the level of 1l and above were Haijiao, Langgang, Huaniao and Tanhu, and the 14 stations such as Shengsi reached the level of 10.Among them, at 3:04 on the second day, a north to northeast wind of 40.4m/s (level 13) appeared on the sea reef, and its wind and rain intensity was comparable to that of the typhoon.
Circulation background analysis
At 14:00 on May 31, the surface map shows that the eastern coast of China is at the rear of the high pressure, and there is an inverted trough in the east of Taiwan and the north top develops into a low-pressure circulation.At 2:00 on June 1, the surface low-pressure circulation moved to the coastal area of southern Zhejiang, gradually forming a cyclone center of 1007.5hPa. At 8:00, the 6-hour precipitation near the cyclone center was generally 20-30mm, and the maximum Yuhuan reached 52mm.By 11:00, the surface cyclone center has further developed, forming a 1005.0hPa cyclone center in the coastal area of central Zhejiang.At 20:00, the center of the cyclone moved to Zhoushan sea area, the intensity was strengthened, and the central pressure dropped to 1000 hPa.Because the Yellow Sea to the Sea of Japan was controlled by the surface high pressure at that time, the surface cyclone and the gradient of the north high pressure were superimposed, which directly caused the gale in Zhoushan sea area.Then the cyclone slowly moved eastward.At 2:00 on the second day, the center of the surface cyclone moved to 127 ° E and 30 ° N,Cyclonic circulationFurther strengthening, the strong decompression effect enables the explosive development of marine cyclones.
At 500hPa in the upper air, there is blocking high pressure in Wudong, and there is a vortex center near Beihu Lake.A small trough was split from the vortex center and moved eastward. At 8:00 on June 1, the trough line moved to the area of Shandong and Anhui at a slow speed and the bottom of the trough extended to 28 ° N. At the same time, a 576hPa vortex center was generated in Anhui with a - 12 ℃ cold center.At 20:00, the center of the vortex moved to the Yangtze River estuary, and the bottom of the trough further extended southward to 27 ° N, further strengthening. The northerly wind behind the trough reached 22m/s, carrying weak cold air to spread southward.On the 31st, there was a shear line at 30 ° N at 700hPa, and there was a high pressure ridge along the coast, with the ridge top at 45 ° N.At 8:00 on June 1, a closed circulation center of 308hPa was formed, which is located at the junction of Jiangsu, Zhejiang and Anhui provinces, with a cold center of - 4 ℃.At 20:00, the vortex moved to Hangzhou Bay, with stronger wind speed and convergence, and the easterly wind on the north side reached 22m/s.At 8:850 hPa on the 31st, there was a southwest low-level jet with a wind speed of more than 16 m/s along the coast of South China. The eastern sea was a high pressure ridge, the top of which extended to the north of 40 ° N, and there was a weak shear line in Jiangxi and Fujian.At 20:00, as the southwest vortex moved eastward, the small high pressure in front of the trough merged into the coastal high ridge, and the wind direction convergence strengthened, so that the shear line was raised to the north.At 8:00 on the 1st, the convergence center moved to the junction of Zhejiang and Anhui, and the wind speed increased to 16m/s.From the east sea, cold advection is transported to the Yangtze River estuary.At 20h144hPa, the closed center was moved to Hangzhou Bay, and the wind speed at Shanghai Station reached 18m/s with the 9 ℃ cold center.At 8:00 on the second day, the vortex in all layers moved to the open sea.
In this process, the southern branch trough is not obvious, and the front area of the southern branch is relatively weak.According to the previous prediction experience, there should be no major development of cyclones.Since the surface inverted trough comes from the sea near Taiwan, rather than moving eastward from the mainland, the inverted trough is developing towards the north.In Zhoushan sea area, the vortex developed from a high trough was encountered, and the upper three-layer low value system was superimposed on the ground trough, causing the trough to strongly develop into a cyclone in the East China Sea.The weak wave on the ground meets the favorable situation field at high altitude and develops rapidly.It is different from the typical Jianghuai cyclone development model.
research conclusion
The development mechanism of the cyclone on June 1, 2006 can be summarized as follows:
(1) The surface system of the East China Sea cyclone came from the sea trough near Taiwan Island, which is different from the previous cyclone trough from West China, and is somewhat like the development of tropical low value systems.
(2) During the eastward movement of the high level trough, a closed high level cold vortex is generated near Anhui. The vortex is relatively deep. When the coastal area of northern Zhejiang enters the sea, it just meets the northward developing surface inverted trough. The vertical coupling of the two systems, that is, the vertical coupling of the high and low level systems, leads to the explosive development of the surface cyclone system.
(3) The dry cold advection behind the high trough intrudes into the cyclone circulation, which increases the baroclinic instability and promotes the development of convection and cyclones in the lower troposphere.The large-scale high trough provides a favorable environment for the development and maintenance of cyclones through the positive vorticity transport in front of the trough and the strengthening of the baroclinic instability by the cold and warm advection in front of and behind the trough.Similarly, the upper jet also passes the divergence andWarm advectionProvide a favorable environment for the development and maintenance of cyclones.
(4) The lifting of the strong vorticity advection in the middle and lower layers in Zhoushan sea area produces precipitation, and the latent heat release is caused by water vapor condensation, which further causes the development of the surface cyclone system. At this time, the cyclone and precipitation form a positive feedback mechanism.The latent heat release is excited by the upward movement caused by the baroclinic instability in front of the high trough and the divergence on the right side of the jet exit area, which plays an important role in the development of the cyclone.[2]
