Scientific knowledge about meteorology

El Nino is a phenomenon that occurs in the ocean, and its notable feature is the abnormal warming of seawater in the eastern and central equatorial Pacific.

Because tropical marine areas receive more solar radiation, the seawater temperature is correspondingly higher. 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 accumulate continuously and become the highest sea surface temperature in the world, with the sea surface temperature above 29℃. On the contrary, the SST in the equatorial eastern Pacific is relatively low, generally 23 ~ 24℃. Due to the distribution characteristics of sea surface temperature field, the tropical western Pacific presents updraft and low pressure.

Under normal circumstances, the western Pacific has a strong upward movement and abundant precipitation. In the equatorial Middle East Pacific, the atmosphere is sinking and there is little precipitation. When the El Nino 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 in the equatorial western Pacific, resulting in severe drought there. However, in the equatorial Middle East Pacific, due to the rising sea surface temperature, the upward movement is strengthened, which leads to an obvious increase in precipitation and heavy rain.

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. 1998, China suffered a catastrophic flood disaster which was rare in history, and El Ni? o was one of the most important influencing factors.

Because El Nino has brought great disasters to the whole world, it has become an important topic in meteorological and oceanographic research.

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 there is a "sudden change in weather", 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 (frontal surface, that is, the interface between cold air and warm air mass), especially in winter and spring, when the cold air in the north moves southward from time to time, the frontal activity is more frequent, which often induces colds or other diseases.

People's cold symptoms will be different in different seasons. The so-called "four-season colds" are wind-cold colds (caused by cold in winter or cooling in spring), wind-heat colds (caused by high temperature in spring or rising temperature in autumn and winter), wet cold or summer colds (caused by high humidity and high temperature in summer) and dry colds (caused by dry air in autumn). Among them, the first two cold symptoms are common headache, fever, stuffy nose and runny nose, while the third cold is often accompanied by chest tightness and joint pain, while the dry-hot cold is generally accompanied by dry nose, dry throat, cough with no or little phlegm, thirst and red tongue.

Therefore, "conforming to nature" 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, it is necessary to change clothes and quilts in time and keep warm to prevent colds and colds. In one or two days after the sudden change of weather, you should go to public places as little as possible to prevent colds.