"Storm Tsunami"-What are the causes and effects of storm surge?

Storm surge is a disastrous meteorological phenomenon. Due to severe atmospheric disturbances, such as strong winds and sudden pressure changes (usually referring to disastrous weather systems such as typhoons and extratropical cyclones), the tidal level in the affected sea areas greatly exceeds the normal tidal level, which is called storm surge. It can also be called "storm increasing water", "storm tsunami", "meteorological tsunami" or "tidal wave".

According to the nature of storms, storm surges are usually divided into two categories: typhoon storm surges caused by typhoons and temperate storm surges caused by temperate cyclones.

"Storm Tsunami"-storm surge (1) Typhoon storm surge, which is more common in summer and autumn. Its characteristics are fierce, fast, strong and destructive. Typhoon storm surges occur in all marine countries and coastal areas affected by typhoons.

(2) Temperate storm surges mostly occur in spring and autumn, and also occur in summer. Its characteristic is that the process of increasing water is relatively gentle, and the height of increasing water is lower than that of typhoon storm surge. It mainly occurs in mid-latitude coastal areas, mainly distributed in the North Sea coast of Europe, the east coast of the United States and the northern coastal areas of China.

Storm surge disaster factors

Whether the storm surge can cause disasters depends largely on whether its maximum storm tide level overlaps with the high tide level in the astronomical tide, especially with the high tide level in the astronomical tide period. 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 the astronomical high tide level, 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 0/94 deaths170km of seawall damaged, 0/933 hectares of farmland affected/kloc-0, and 333,000 hectares damaged, resulting in 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 high tide. 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.

Historical disaster of storm surge

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.

Disaster 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 storm water increase reached 3.45 meters, and the highest tidal level reached 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 reached 6.5438+0.50 million, and the direct economic loss was 85.2 billion yen (654.38+0.959).

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 coastal areas of the Baltic Sea, 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 the 20th 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 government 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.

According to statistics, from Han Dynasty to A.D. 1946, there were 576 mega-tidal disasters in China's coastal areas, and the number of people killed in a tidal disaster ranged from hundreds to tens of thousands to as many as 654.38+10,000.

In recent decades, China has been hit by storm surges many times, which has also caused huge economic losses and casualties. 1956 No.1 12 typhoon triggered a severe storm surge, which flooded 400,000 mu of farmland in Zhejiang Province, killing 4,629 people. No.3 strong typhoon 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. With the efforts of the local government and army, there are still 1554 deaths, but compared with the storm surge 1922 with the same intensity in the same area, the death toll has dropped by 98%. 1On April 5th, 964, an extratropical cyclone storm surge occurred in the Bohai Sea, which caused seawater to flood into the land for 20-30 kilometers, causing 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 ~ 40 kilometers.

Since the beginning of 2 1 century, the storm surge has not spared China, which has caused great losses in the coastal areas of China in recent years.