National Climate Center:
There will be a weak to moderate La Niña event this winter
Science and Technology Daily News (Reporter Fu Lili) On November 27, the National Climate Center announced that according to the latest sea temperature monitoring data, the equatorial Central and Eastern Pacific will enter La Nina in October 2021, and it is expected that a weak to moderate intensity may develop in winter. La Nina incident.
According to experts, La Niña refers to the phenomenon of continuous abnormally cold sea surface temperature in a wide range of the equatorial Central and Eastern Pacific Ocean, which will cause anomalies in the earth's climate.
According to the national standard of "El Nino/La Nina Event Discrimination Method", when the key area (Nino 3.4 area, that is, the area between 120° to 170° west longitude and 5° north latitude), the 3-month moving average sea surface temperature is lower than the climate When the average state is 0.5℃, it enters the La Niña state, and it lasts for more than 5 months to form a La Niña event.
The latest SST monitoring shows that the moving average index of key areas in the last three months (August-October) is -0.52℃, which indicates that the SST in the equatorial Central and Eastern Pacific has entered the state of La Niña.
In terms of tropical atmospheric characteristics, in October 2021, convective activities in parts of the tropical northwest Pacific were more active than usual, while convection activities in most of the tropical central and eastern Pacific were suppressed. At the same time, in the vertical zonal circulation anomaly field along the equator, the equatorial Middle East The Pacific Ocean is an abnormal sinking movement, while the equatorial western Pacific is controlled by an abnormal ascending movement, which is consistent with the anomalous distribution of tropical convection activities, showing the response characteristics of the tropical atmosphere to the cold sea temperature in the equatorial Central and Eastern Pacific.
According to the current status of ocean atmospheric circulation in the equatorial Pacific and the prediction results of domestic and foreign climate dynamic models and statistical methods, it is expected that the La Niña state will continue in the next three months, and may reach its peak in winter (December 2021 to January 2022), forming once Weak to moderate La Niña events.
What impact does La Niña have on the global climate and our country's climate?
From a global perspective, when most La Niña events occur, precipitation decreases in areas near the coast of South America, while precipitation increases in Indonesia and eastern Australia; droughts often occur in central Africa, southeastern United States, and northeastern Brazil, India, and southern Africa. It is prone to flooding.
As for the impact on my country’s climate, it can be seen from the two aspects of temperature and precipitation-in the winter when most La Niña events reach their peak, the cold air activities affecting my country are more frequent and stronger than usual, and most of the central and eastern parts of my country The regional temperature is more likely to be lower than normal. The tropical and subtropical regions are affected by the La Niña event, which will cause the water vapor conditions in southern my country to deviate significantly from the same period in normal years, which is not conducive to the formation of precipitation.
Experts said that from historical data, the temperature in the central and eastern regions of my country in La Niña winter is often low.
However, it is also necessary to point out that in the context of global warming, the factors affecting my country's winter climate are more complicated. In addition to the La Niña event, there are also Arctic sea ice melting, changes in snow cover in Europe and Asia, and sea temperature abnormalities in other sea areas.