What does "desert blossom" mean in Peru?

The coastal area of Peru is long and narrow from north to south, with a width of only 30 ~ 130 km. There are mobile sand dunes widely distributed on the ground, which belongs to the tropical desert climate. The annual average temperature in this area is above 25℃, the annual precipitation is less than 50 mm, and the southern part is less than 25 mm. The climate is hot and dry. But in some years, the precipitation suddenly doubles, and more lush plants will grow in the desert, which can blossom and bear fruit. This phenomenon is called "desert flowering".

So, why does the desert bloom? Marine meteorologists believe that this is closely related to the emergence of the "El Niñ o" phenomenon. The so-called "El Nino" means "El Nino" in Spanish, because it happens every 2-7 years, but it happens every time around Christmas, so Americans give it a good name "El Nino".

However, "El Nino" has brought a series of disasters to mankind. Once it happens, it usually lasts for several months or even more than a year. It not only makes Peru's coastal climate unusually warm and rainy, but also makes Australia's jungle catch fire because of drought and heat. Heat waves and snowstorms compete in the North American continent; Hawaii was hit by a tropical storm; California suffered from floods, and severe droughts occurred in Oceania and West Asia. There will be large-scale soil cracking in Africa; There will be floods in Europe, droughts in southern China, and coastal fisheries will reduce production; The national temperature is low, and grain production will be reduced in a large area.

From 1982 to 1983, a serious "El Nino" phenomenon occurred, which harmed the global 1/4 area and the global economic loss was estimated to be 8 billion dollars.

How did "El Nino" happen? It turns out that on the north and south sides of the equator, two ocean currents from east to west are formed because of the southeast trade winds and northeast trade winds blowing all the year round. The seawater flowing out of the East Pacific Ocean is supplemented by the upwelling of the lower seawater. Because the lower seawater is cold, the water temperature in the Pacific Ocean is "seesaw" with high in the west and low in the east. Catfish and seabirds along the coast of Peru in the eastern Pacific have lived happily in this cold sea area for many years. After the two equatorial currents flowing from east to west reach the other side of the ocean, some of them form a reverse current and then flow eastward across the Pacific Ocean. This warm current countercurrent is called equatorial countercurrent. However, in some years, due to the sudden weakening of the southeast trade wind in the southern hemisphere, the southern equatorial current also weakened, and the rising cold water in the eastern Pacific decreased, while more warm water flowed into the eastern Pacific with the equatorial countercurrent. In this way, the "seesaw" of the Pacific water temperature becomes high in the east and low in the west.

However, the mechanism of "El Nino" is still a mystery, and the reason for this phenomenon is still unclear.

Finally, Walker, a seismologist at the University of Hawaii, pointed out that since 1964, the occurrence time of five "El Nino" events is closely consistent with the periodic phenomenon that earthquakes occur at the boundary between two moving plates of the earth. However, whether there is a causal relationship between the two remains to be further explored.

Other scientists believe that the El Niñ o phenomenon is related to a global climate change system called the Southern Oscillation, which will affect the strength of the trade winds in the southern hemisphere. An international research project called 70GA (Tropical Ocean and Atmosphere) is exploring the mystery of El Nino.

Scientists in China put forward the hypothesis that "El Nino" may be related to the change of the earth's rotation speed. They compared the data of the change of the earth's rotation speed after the 1950s, and found that as long as the annual variable of the earth's rotation slows down rapidly for two years and the value is large, the "El Nino" phenomenon will occur. Due to the slow rotation of the earth, seawater and the atmosphere moving with the earth will produce an eastward relative velocity under the action of inertial force, which is the largest near the equator. According to calculation, the relative velocities of seawater and atmosphere near the equator can be 0.5 cm per second and 1 m per second, which weakens equatorial ocean currents and trade winds from west to east, resulting in changes in water temperature along the east and west coasts of the Pacific Ocean. At present, advanced means such as meteorological satellites, ocean survey ships and buoy robots have been widely used in El Niñ o research. Some scientists turned to geological research, that is, from the accumulation of silt in some coastal estuaries to analyze the "El Niñ o" relics that occurred in the distant past.