Meteorological knowledge

El Nino is a phenomenon occurring in the ocean, which is characterized by abnormal warming of seawater in the eastern and central equatorial Pacific.

Because tropical marine areas receive more solar radiation, the temperature of seawater is relatively high. In the tropical Pacific Ocean, the equatorial current flows from the eastern Pacific Ocean to the western Pacific Ocean due to the traction of the east equatorial trade wind, which makes the high warm current in the western Pacific Ocean gather, making it the highest water temperature in Shanghai in the world, and the surface temperature of seawater is above 29℃. On the contrary, the seawater temperature in the equatorial eastern Pacific is relatively low, generally 23 ~ 24℃. Due to the west high sea surface temperature field,

Under normal circumstances, the western Pacific has a strong upward movement and abundant precipitation. In the equatorial Middle East Pacific, the atmosphere sinks and there is little precipitation. When the El Ni? o phenomenon occurs, a large amount of warm seawater flows from the equatorial western Pacific to the equatorial eastern Pacific, which leads to the decrease of seawater temperature, the weakening of atmospheric upward movement and the decrease of precipitation, resulting in severe drought there. In the equatorial Middle East Pacific, due to the increase of SST, the upward movement is strengthened and the precipitation is obvious.

El Nino phenomenon is the result of unstable interaction between ocean and atmosphere. According to statistics, every strong El Ni? o phenomenon will lead to global climate anomalies and bring huge economic losses. 1997 is a strong El Nino year, and its strong influence lasted until the first half of 1998. El Nino is one of the important factors affecting the historical drought in China in 1998.

El Nino has become an important research topic in meteorology and oceanography because it has brought great disasters to the whole world.

Cold and weather

In many places in China, colds are called "catching cold", which shows that colds are closely related to weather conditions. Colds occur all year round, especially in winter and spring, because influenza viruses are easy to parasitize in low temperature and dry cold environment. Chinese medicine also believes that when the climate changes suddenly and the temperature is abnormal, the wind pathogen virus is most likely to attack the human body.

Clinical practice also shows that whenever "sudden weather change" occurs, the number of people who catch a cold often increases suddenly. "Sudden weather change" is mainly manifested in the drastic changes of meteorological factors such as temperature, air pressure, precipitation, wind and humidity, which are generally brought by the frontal weather system (the front, that is, the interface between cold air and warm air mass), especially in winter and spring, the cold air in the north moves southward from time to time, and the frontal activities are more frequent.

The symptoms of human cold will be different in different seasons, that is, the so-called "four-season cold": wind-cold cold (caused by cold in winter or cooling in spring), wind-heat cold (caused by high temperature in spring or rising in autumn and winter), cold-dampness or summer-dampness (caused by high humidity and temperature in summer) and cold-dryness (caused by dry air in autumn). The first two cold symptoms are common headache, fever and stuffy nose and runny nose.

Therefore, "adapting to the weather" should be the first principle to follow in preventing colds. Specifically, it is necessary to pay attention to listening to and watching weather forecast programs on the premise of being familiar with the laws of local weather and climate change. When the weather changes suddenly, you should change clothes and quilts in time, keep warm and prevent colds. In a day or two after the sudden change of weather, you should go to public places as little as possible to avoid catching a cold.