Typhoons rarely visit Shanghai. Why?

Generally speaking, Shanghai is located between Jiangsu and Zhejiang, but compared with Jiangsu and Zhejiang, the number of typhoons in Shanghai is indeed less, which is related to the length of Shanghai coastline and the latitude of Shanghai. Therefore, typhoons that landed off the coast of China are often ridiculed as having no "Shanghai brand".

First, let's take a look at the length of Shanghai coastline. Although it is not particularly short as a single city, especially Chongming Island, the coastline of Shanghai is second to none among all cities in China. However, among all the provinces and regions in the southeast coast, the vertical intersection between the north and the south of Shanghai coastline is the shortest, which reduces the probability of typhoon landing, just like being shot. This reason is purely numerical probability difference, which is easy to understand.

Another reason is the latitude of Shanghai, which is between 30 40 ′ and 365 438+0 53 ′ north latitude, and 30 ′ north latitude is the dividing line between the low-latitude circulation and the mid-latitude circulation. Low latitude circulation produces easterly belt, while middle latitude circulation produces westerly belt. The typhoon that affects our country is basically formed in the equatorial low latitude area. In the process of advancing to the northwest, it meets the westerly belt at 30 degrees north latitude, so the typhoon will turn northeast in this area and just bypass Shanghai.

Finally, according to the meteorological data of previous years, the probability of typhoon landing in Zhejiang and Fujian, south of Shanghai, is relatively high, because the cyclone energy is closely related to latitude and temperature during the process of typhoon landing in China. In normal meteorological years, typhoons basically turn westward in low latitudes, affecting Zhejiang and Fujian. However, when the climate is abnormal, the latitude of the subtropical ridge line rises, and only when the typhoon turns to the west can it make a direct attack on Shanghai.

It should have a lot to do with the latitude and depth of the sea where Shandong Peninsula is located. Because in the whole Bohai Bay, the average seawater depth is less than 100 meter, and most seawater depths are only about 50 to 60 meters. Even if typhoons and storm surges come, the seawater at this depth will be slightly weakened because of its low depth.

Coupled with latitude (north), typhoons are mostly generated in the south (Philippines, northern South China Sea). The typhoon swept from south to north. In Shandong, it has been greatly weakened. Even if it is strengthened, it will not happen in a hundred years, and it will be weakened by the low water depth in Bohai Bay.