What is a storm surge?
Analysis:
Storm surge disaster
(A) the main characteristics of storm surge
Storm surge refers to the abnormal rise of sea level caused by strong atmospheric disturbances such as tropical cyclones (typhoons, hurricanes) and temperate cyclones. The sea level fluctuation recorded by coastal tide gauge stations or estuary water level stations is usually a comprehensive feature of sea level change caused by long-wave vibration such as astronomical tide, storm surge and tsunami. The general tide gauge has filtered out the sea surface fluctuation caused by short-period waves for a few seconds. If the storm surge happens to coincide with astronomical events (especially astronomical events during the astronomical tide), the storm surge is often accompanied by violent wind and waves, which go upstream with the river flood, and often make the tidal waves in the affected coastal areas soar, even the tidal waves destroy the seawalls and engulf the docks, factories, towns and villages, making it impossible for materials to be transferred and people and animals to escape, thus causing great disasters.
Some people call storm surge "storm tsunami" or "meteorological tsunami". In China historical documents, it is often called "sea overflow", "transgression", "tsunami" and "tidal wave", and storm surge disaster is called "tidal disaster". The spatial range of storm surge is generally from tens of kilometers to thousands of kilometers, and the time scale or period is about 1- 100 hours, which is between earthquake tsunami and low-frequency astronomical tide wave. However, sometimes the affected area of storm surge will move with the movement of atmospheric disturbance factors, so sometimes a storm surge process can affect one or two thousand kilometers of coastal areas for several days.
Scholars at home and abroad mostly divide storm surges into typhoon storm surges caused by tropical cyclones (or tropical storm surges, which are called hurricane storm surges in North America and tropical cyclone storm surges along the Indian Ocean coast) and temperate storm surges caused by temperate weather systems such as temperate cyclones. China is one of the few countries in the world where two kinds of storm surge disasters are very serious. Storm surge disasters can occur all year round, and the coastal areas from south to north are not spared. Storm surge is usually named after the weather system that causes storm surge at home and abroad. For example, the storm surge caused by typhoon 1980 (internationally known as typhoon Joe) is called typhoon 8007 or storm Joe; 1969 The storm surge caused by Hurricane Camille, which landed in North America, is called "Camille storm surge".
Whether the storm surge can cause disasters depends largely on whether the maximum storm tide level overlaps with astronomical tide, especially with the astronomical tide cycle. Of course, it also depends on the geographical location, coastal morphology, coastal and seabed topography of the affected areas, especially the socio-economic (disaster-bearing body) situation in the coastal areas. If the maximum storm tide level coincides with astronomical tide, it will lead to catastrophic tidal disasters, such as typhoon storm surge of 8923 and 92 16. From August 28th, 1992 to September 28th, 1 2008, under the joint influence of 16 strong tropical storm and astronomical tide, a storm surge disaster with the most extensive influence and the most serious loss occurred in the eastern coast of China since 1949. Flood disasters have spread to Fujian, Zhejiang, Shanghai, Jiangsu, Shandong, Tianjin, Hebei and Liaoning provinces and cities. The combined action of storm surge, huge waves, strong winds and heavy rain has caused the coastline of nearly 10,000 kilometers from Dongshan Island in Fujian in the south to the coast of Liaoning Province in the north to be attacked to varying degrees. The affected population reached more than 20 million, with 193 deaths, damaged seawalls 1 170 kilometers, affected farmland1933,000 hectares, damaged 333,000 hectares and direct economic losses of more than 9 billion yuan.
Of course, if the storm surge level is very high, it will also cause serious tidal disasters, although there is no astronomical tide or * * *. This is the case with the storm surge of Typhoon No.8007, which coincided with the normal tide in the astronomical tide. Due to the ultra-high storm surge level of 5.94 meters, it still caused serious storm surge disasters. According to the opinions of storm surge experts at home and abroad, storm surge disasters are generally divided into four grades, namely, extra-large tidal disasters, severe tidal disasters, large tidal disasters and mild tidal disasters. See table 14-2 for the reference disasters and storm surge levels corresponding to tidal disasters at all levels. The storm surge disasters in China discussed in this section include the extraordinary tidal disasters and some serious tidal disasters along the coast of China from 1949 to 1995.
(2) Storm surge disaster
Storm surge disaster ranks first in marine disasters, and most of the major coastal disasters caused by strong storms in the world are caused by storm surge. On the coast of the Bay of Bengal, a tropical cyclone storm surge disaster 1970 1 13 shocked the world. The storm surge increased the water level by more than 6 meters, claimed 300,000 lives, drowned 500,000 livestock and left more than 654,380,000 people homeless in the Ganges Delta. 199 1 April, another extraordinary storm surge claimed130,000 lives despite warnings of tropical cyclones and storm surges. 1On September 26th, 959, the Nagoya area at the top of Ise Bay in Japan suffered the worst storm surge disaster in Japanese history. The maximum rainstorm water increase reaches 3.45 meters, and the maximum position reaches 5.8 1 meter. At that time, the water level along the coast of Ise Bay soared, and the storm surge provoked thousands of waves to rush to the embankment, and the moisture-proof seawall was washed away in a short time. It caused 5 180 deaths, with a total of more than 70,000 casualties. The affected population reached10.5 million, and the direct economic loss was 85.2 billion yen (current price). The United States is also a country with frequent storm surges. Like China, there are both hurricane (typhoon) storm surges and temperate gale storm surges. 1969 Hurricane Camille, which landed on the Gulf Coast of the United States, triggered a storm surge of 7.5 meters, which is the first storm surge record in the world so far. Historically, the Netherlands has been submerged by sea water more than once, and it has regained the submerged land from the ocean more than once. These lands protected by tidal dikes account for about 3/4 of the total land in the Netherlands. The Netherlands, Britain, the Baltic coast of the former Soviet Union, the northeastern coast of the United States and the Bohai Sea in China are all prone to temperate storm surges.
In the history of China, the loss of life and property caused by storm surge is shocking. 1782, a strong temperate storm surge in Qing dynasty, which affected 7 counties from Wudi to wei county. 1On April 28th and 29th, 895, a storm surge occurred in Bohai Bay, which destroyed almost all the buildings in Dagukou, turned the whole area into a "Zeguo" and killed more than 2,000 people in Haiphong Camp. On August 2nd, 1922 strong typhoon storm surge hit Shantou area, causing serious storm surge disaster. According to historical records and textual research by Zhu Kezhen, a famous meteorologist in China, more than 70,000 people were killed and more people were homeless. This is a storm surge disaster with the largest death toll in China since this century. According to Chaozhou Chronicle, the typhoon "rocked the mountain, uprooted trees to build houses, and suddenly plunged into the sea. The rain is pouring down, the water depth of the flat land is more than ten feet, the coastal area is less than ten feet, and there are many waves in the countryside. " "Those who were particularly seriously affected, such as the sand outside Chenghai, lost their lives and property." This county has a village with a population of more than 65438+100000, and more than 7000 people died in this storm surge disaster. The local * * * turned a blind eye to this, and as a result, the epidemic raged and more than 2,000 people died. The recorded storm surge value is 3.65 meters, and the typhoon wind force exceeds 12. There have been many very serious storm surges in Shanghai in history. The most serious one occurred in 1696. "On the first day of June in the thirty-fifth year of Kangxi, there was a heavy rain and the weather was too dry. In an instant, the ditches flooded and the road was filled with cheers and thunder. After the second watch, there was a sudden tsunami and a hurricane again. The tide is magnificent and surging, rushing into the coast for hundreds of miles. Baoshan stretches for six miles and eighteen miles, and the water level is higher than that of the city. Jiading, Chongming, Wusong, Chuansha, Zhelin Eighth and Ninth Regiments, etc. Drifting in thousands of feet, there were 18,000 cooks and more than 100,000 people drowned. It was stormy that night, and people no longer cared about each other, so there was no way to run around. In the morning, the water receded and the bodies piled up like mountains, which was terrible. " This is the deadliest storm surge disaster in China since it was recorded in writing.
According to statistics, during the year 2000 from Han Dynasty to A.D. 1946, there were 576 catastrophic tidal disasters along the coast of China, and the number of people killed in a tidal disaster ranged from several million to tens of thousands to hundreds of thousands.
In the 40 years since the founding of the People's Republic of China, China has been hit by storm surges many times, which has also caused huge economic losses and casualties. 1956 no 12 (Wanda) Typhoon caused a severe storm surge, which flooded 400,000 mu of farmland in Zhejiang Province and killed 4,629 people. Typhoon No.3 (Viola) 1969 landed in Huilai, Guangdong Province, causing a severe storm surge disaster in Shantou. Shantou city was flooded, the streets were flooded1.5-2m, and the Niu Tianyang levee was washed away. Thanks to the efforts of local authorities and the army, 65,438+0,554 people were still killed. However, compared with the 1922 storm surge with the same intensity in the same area, the death toll decreased by 98%. 1The extratropical cyclone storm surge that occurred in the Bohai Sea on April 5, 964 caused seawater to flood into the land for 20 to 30 kilometers, which caused the most serious storm surge disaster along the Bohai Sea since 1949. The Yellow River Estuary is supported by tides, and floods have aggravated the disaster situation, and people's lives and property in Laizhou Bay and the Yellow River Estuary have suffered heavy losses. The other time was April 23rd, 1969. The temperate storm surge in the same area makes the coastal seawater from Wudi to Changyi and Laizhou invade for 30 to 40 kilometers. According to statistics, during the 45 years from 1949 to 1993, there were 269 typhoon storm surges with the maximum water increase exceeding 1 m in the process of * * * in China, including 49 storm surges with a storm surge level exceeding 2 m and 10 with a storm surge level exceeding 3 m. * * * caused 14 catastrophic tidal disasters and 33 severe tidal disasters, compared with 17 tidal disasters and 36 mild tidal disasters. In addition, there were 547 temperate storm surges with the maximum water increase exceeding 1.950- 1.993 * * along the Bohai Sea and the Yellow Sea in China, of which 57 were over 2m and 3 were over 3m. It caused 4 serious tidal disasters, compared with 6 tidal disasters and 6 1 mild tidal disasters.
In the past 40 years, although the coastal population has increased rapidly, the number of people who died from tidal disasters has decreased significantly, which cannot but be attributed to the superiority of our social system and the success of storm surge forecasting and early warning. However, with the development of industry and agriculture in coastal towns and the increase of coastal infrastructure, the number of disaster-bearing bodies is increasing, but the direct and indirect losses of each storm surge are also increasing. According to statistics, the average annual economic loss of storm surge in China increased from about 65.438+0 billion yuan in the 1950s to about 2 billion yuan in the late 1980s, reaching 9.32 billion yuan in the early 1990s, and 65.438+0.992 and 65.438+0.79 billion yuan in the early 1990s respectively. Storm surge is becoming an important part of coastal opening and social and economic development.