According to monitoring by the National Climate Center, in October of this year, the equatorial Middle East Pacific has entered a La Ni ñ a. As of December 15th, La Ni ñ a status is still ongoing. What is La Ni ñ a state? According to the national standard "Method for Distinguishing El Ni ñ o/La Ni ñ a Events" (GB/T 33666-2017), the average sea surface temperature anomaly within the equatorial central eastern Pacific region is defined as the NINO3.4 index. When the 3-month moving average of this index is less than or equal to -0.5 degrees Celsius, it is considered that the equatorial central eastern Pacific has entered a La Ni ñ a state. When the duration of La Ni ñ a is greater than or equal to 5 months, it is determined to form a La Ni ñ a event. It is expected that the La Ni ñ a state will last until early 2026, with a duration of less than 5 months, and the possibility of forming a La Ni ñ a event is relatively low. ”Zhang Daquan, Deputy Director of the Climate Prediction Department at the National Climate Center, said. What are the potential impacts of the ongoing La Ni ñ a state? Generally speaking, during the winter when a La Ni ñ a event occurs, a cyclonic anomalous circulation prevails over the northwest Pacific and South China Sea. The northwesterly winds are conducive to guiding cold air from the north southward, strengthening the East Asian winter monsoon and leading to mainly lower temperatures in the central and eastern regions of China. Zhang Daquan stated that due to factors such as global warming, winter temperatures in China have frequently become warmer under the background of La Ni ñ a since the beginning of this century, and even experienced warm winters, such as the winter of 2020/2021. At the same time, cyclonic anomalous circulation can suppress the transport of water vapor from the northwest Pacific, South China Sea, and Bay of Bengal to southern China, leading to sustained low precipitation and easily causing consecutive droughts in winter and spring. In the summer of the following year after the La Ni ñ a event, the position of the western Pacific subtropical high is often northward, and the East Asian summer monsoon is stronger, which is conducive to more precipitation in northern China. However, the precipitation in the Yangtze River Basin is less than the same period of the year, making it prone to high temperatures and droughts. What weather processes will occur in China this winter as La Ni ñ a continues? It is expected that the temperature in most parts of China will be close to the same period as usual and slightly higher this winter, but the temperature will fluctuate significantly, with frequent strong cooling and warming events. In terms of precipitation, the overall precipitation in the country is relatively low, and the spatial distribution will be "more in the north and less in the south". During winter, there may be periodic strong winds, strong cooling, and snowfall weather processes in Northeast China, North China, Inner Mongolia, Xinjiang, and other regions; Periodic low temperatures and freezing weather with rain, snow, and ice may occur in some areas of northern and southwestern China; During the winter and spring seasons, temperatures in southeastern China, eastern central China, and eastern southern China are relatively high, with less precipitation, resulting in a higher risk of consecutive droughts in winter and spring. A comprehensive reminder that the La Ni ñ a situation will continue this winter, and various regions can make targeted production and living preparations according to the risk of meteorological disasters. (New Society)