What impact will the ongoing La Nina state have on China this winter?
The National Climate Center's monitoring shows that in October this year, the equatorial Central and Eastern Pacific has entered a La Nina state. As of December 15th, the La Nina state was still ongoing.
What is La Nina status? According to the national standard "Method for Discriminating El Nino/La Nina Events" (GB/T 33666-2017), the average value of the sea surface temperature anomaly within the equatorial Central and Eastern Pacific is defined as the Nino 3.4 index. When the three-month moving average of this index is less than or equal to -0.5 degrees Celsius, it is considered that the central and eastern equatorial Pacific has entered a La Nina state. When the duration of La Nina is greater than or equal to five months, it is determined that a La Nina event has formed.
It is expected that the current La Nina state will last until early 2026, with a duration of less than five months. The possibility of a La Nina event forming is relatively low. Zhang Daquan, deputy director of the Climate Prediction Office of the National Climate Center, said.
What could be the possible impacts if La Nina persists? Generally speaking, during the winter when a La Nina event occurs, cyclonic abnormal circulation prevails over the northwest Pacific and the South China Sea. The northerly wind on its west side is conducive to guiding the cold air from the north to move southward, strengthening the East Asian winter monsoon, resulting in mainly low temperatures in the central and eastern regions of China.
Zhang Daquan said that due to factors such as global warming, since the beginning of this century, the situation of warmer winters in China under the La Nina background has occurred frequently, and even warm winters have emerged, such as in the winter of 2020/2021. Meanwhile, the cyclonic abnormal circulation will suppress the transport of water vapor from the northwest Pacific, the South China Sea and the Bay of Bengal to the southern regions of our country, resulting in persistently low precipitation and easily triggering consecutive droughts in winter and spring. In the summer following a La Nina event, the position of the Western Pacific subtropical high pressure is often further north, 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 average of the same period in previous years, making it prone to high temperatures and droughts.
With the La Nina state persisting, what weather processes will there be in China this winter? It is expected that this winter, the temperature in most parts of our country will be close to or higher than the average of the same period in previous years. However, the temperature will fluctuate significantly, with frequent strong temperature drops and rises. In terms of precipitation, the overall precipitation across the country is relatively low, and it will show a spatial distribution of "more in the north and less in the south".
In winter, there may be intermittent strong winds, severe temperature drops and snowfall in Northeast China, North China, Inner Mongolia, Xinjiang and other places. Some areas in the north and southwest of our country may experience intermittent low-temperature and rain, snow and ice weather. During winter and spring, the southern part of East China, the eastern part of Central China and the eastern part of South China will experience higher temperatures and less precipitation, which increases the risk of consecutive droughts in winter and spring. Zhang Daquan reminds that the La Nina state will persist this winter, and localities can make some targeted preparations for production and life based on the risks of meteorological disasters.
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