Will this winter be colder?

summary

Since this autumn (September 1 to October 9, 2022), my country's climate has generally shown "warm and dry" characteristics. The national average temperature is 16.7℃, 0.6℃ higher than the same period last year; the national average precipitation is 70.9 mm, 9.9% less than the same period last year.

The National Climate Center predicts that the current ongoing La Niña event will continue into the winter of 2022/2023.

Before the mid-1980s, there was a good correspondence between La Niña events and colder winters in my country. However, against the backdrop of global warming, the frequency of warm winters has been increasing since 1986. In the past eight La Niña events, the proportion of colder and warmer winters was half each. La Niña events have an important impact on regional climate anomalies in autumn and winter, such as autumn rains in western China, autumn droughts in the south, and autumn floods in the north. It is important to note that La Niña events are only one of the important factors affecting the underlying surface forcing in my country's autumn and winter climate. The National Climate Center will strengthen tracking, monitoring, and judgment, and provide the latest forecast opinions and service information in a timely manner.

1. The current La Niña event is ongoing and is expected to last until the winter of 2022/2023

The latest monitoring results of the National Climate Center show that the current "La Niña" event is continuing. In September 2022, the sea surface temperature in most parts of the tropical central and eastern Pacific was lower than the same period of previous years, with the cold water center value below -1.5℃ (see Figure 1); the sea temperature index in the key sea temperature monitoring area (Niño3.4 area) was -1.03℃, a slight increase of 0.03℃ from August 2022; the tropical atmosphere monitoring index (Southern Oscillation Index, or SOI) was 1.78, an increase of 0.46 from August 2022 (see Figure 2), indicating that the tropical atmosphere responded significantly to the La Niña event; the three-month sliding average index of the sea temperature in the Niño3.4 area from July to September was -0.93℃, a decrease of 0.07℃ from the three-month sliding average index from June to August, indicating that the La Niña event is slowly developing in autumn. The current sea temperature status and the response of the atmosphere to the sea temperature both show the continuation of the La Niña event in the equatorial central and eastern Pacific.

According to the current status of the atmospheric circulation in the equatorial Pacific Ocean and the prediction results of domestic and foreign climate dynamic models and statistical methods, the National Climate Center predicts that the La Niña event in the equatorial central and eastern Pacific will continue until the winter of 2022/2023. In August, the World Meteorological Organization (WMO) predicted based on the Global Long-range Forecast Product Center that the current La Niña event will continue for the next six months, with a probability of 70% from September to November 2022, but the probability will gradually decrease to 55% from December to February 2022/2023.

Figure 1 Global sea surface temperature anomaly distribution in September 2022 (unit: °C)

Fig. 2 Monthly evolution of SST index (℃) and SOI in Niño 3.4 region

2. Analysis of the impact of La Nina on autumn and winter climate

Generally speaking, in the late autumn of the year of a La Niña event (only November is counted here), the temperature in the southern part of Southwest China is lower than the same period of previous years , and the temperature in most other regions is higher than the same period of previous years, especially in southern North China, northern Central China, and southeastern Northwest China; precipitation is less in most parts of China, especially in central East China, central Central China, northern South China, eastern Southwest China, southeastern Northwest China, and central Xinjiang, but precipitation is more in western Northeast China, western Southwest China, and southeastern Tibet .

Usually in the winter after a La Nina event (December of the current year to February of the following year), the main characteristics of abnormal winter temperatures in China are: the temperature in most parts of the country is lower than the same period of previous years , especially in northern North China, southern Northeast China, most of South China, eastern and northern Southwest China, and most of Northwest China. After the La Nina event, China's winter precipitation is mainly manifested as: less precipitation in a large area , especially in the eastern part of Northeast China, along the middle and lower reaches of the Yangtze River, southern Southwest China, and northern Xinjiang; more precipitation in the northern part of Southwest China and eastern Northwest China. However, it is worth noting that the impact of La Nina events on China's winter climate has interdecadal differences . From 1951 to the mid-1980s, the winter temperatures in China during the La Nina events were significantly lower, and cold winters occurred. Against the background of global warming, since 1986, high temperatures in the La Nina events have also occurred from time to time, and even warm winters have occurred.

According to statistics from the National Climate Center, from the 1950s to the 1980s, there were 139 cold air processes in the autumn and winter (September to February of the following year) during the "La Niña" event across the country (34 of which reached the level of cold waves), with the most cold air processes in the autumn and winter of 1972/1973, reaching 24 times. From the 1990s to February 2022, there were 141 cold air processes in the autumn and winter of "La Niña" events (27 of which reached the level of cold waves), with the most cold air processes in the autumn and winter of 2000/2001 and the autumn and winter of 2012/2013, with 23 times.

Among the years when La Niña events occurred, 2008 and 2018 were years with relatively severe low temperature and freezing damage and snow disasters, 2011 was a year with normal to mild low temperature and freezing damage and snow disasters, and 2001, 2012 and 2021 were years with relatively mild low temperature and freezing damage and snow disasters. In October 2008, Tibet suffered the most extensive and intense snowfall weather since meteorological data were available. In October 2018, Heilongjiang and Xinjiang suffered from low temperature and freezing damage and snow disasters; in November, four cold air processes affected my country, and many places such as Xinjiang, Qinghai, and Heilongjiang suffered heavy snow.

On February 3, 2008, a large de-icing vehicle broke ice and cleared the road on the Hunan section of the Beijing-Zhuhai Expressway. Photo/Xinhua News Agency

3. Since this autumn, the national climate has shown "warm and dry" characteristics

Since the autumn of this year (September 1 to October 9, 2022), the national average temperature is 16.7℃, 0.6℃ higher than the same period of previous years, and the 8th highest in the same period since 1961. Except for the western and southern parts of Northeast China, southwestern North China, eastern Southwest China, eastern Shandong, and southern Jiangsu, where the temperature is lower than the same period of previous years, most other parts of the country are close to the same period of previous years or higher. Among them, the temperature in southern Central China, southeastern East China, northern South China, eastern Guizhou, western Inner Mongolia, Gansu, and Xinjiang is 1-2℃ higher than the same period of previous years, among which southern Hunan, southern Jiangxi, northern Guangdong, and northeastern Guangxi are 2-4℃ higher (see Figure 3). The average temperature in Hunan is the second highest in the same period since 1961, and Fujian and Xinjiang are the third highest. A total of 679 national meteorological stations in the country have reached or exceeded the historical extremes of the month, of which 321 stations such as Qingyang, Anhui (40.9℃) and Yangxin, Hubei (40.6℃) have reached or exceeded the historical extremes of the season.

Figure 3 Distribution of average temperature anomalies across the country since this autumn

Since autumn, the national average precipitation has been 70.9 mm, 9.9% less than the same period of normal years, and the seventh lowest in the same period since 1961. Precipitation in the eastern and southern parts of Northeast China, southern North China and eastern Jiangsu, Shanghai, northern and southern Henan, northern Hubei, southern Shaanxi, northern Chongqing, western and eastern Sichuan, southeastern Yunnan, and most of Tibet is 20% to 2 times higher than the same period of normal years, among which southeastern Liaoning, eastern Shandong, and western Tibet are more than 2 times higher; precipitation in most other parts of the country is 20% to 80% lower than the same period of normal years, among which central North China and Fujian, Jiangxi, central and southern Hunan, southern Xinjiang, northwestern Qinghai, western Gansu, and western Inner Mongolia are 80% to 1 times lower (see Figure 4). Fujian, Hunan, and Jiangxi have the least precipitation in the same period of history since 1961, and Beijing is the third lowest; Tibet has the second highest precipitation in the same period of history, and Liaoning is the third highest. A total of 86 national meteorological stations across the country reached or exceeded the historical maximum daily precipitation for the month. Among them, 21 stations including Fushan, Shandong (167.0 mm) and Pikou, Liaoning (157.9 mm) reached or exceeded the historical maximum for the season, and Luxi, Yunnan (181.6 mm) broke the historical maximum.

Figure 4 Distribution of precipitation anomaly percentage across the country since autumn

Additional note: Comparison of climate characteristics of warmer and colder winter years during La Niña events

In the warmer winter years (1998, 2000, 2017, 2020) , the temperature in most parts of the country was close to the normal year or slightly higher. Precipitation was less in the northern part of Northeast China, but precipitation was close to the normal year or higher in most parts of central and eastern China, with precipitation 50% to 100% higher in most parts of North China, northern East China, northeastern Henan, central Inner Mongolia, and northeastern Xinjiang.

In the cold winter years (2007, 2010, 2011, 2021) , the temperature in most parts of the country was close to the normal temperature, and the temperature was lower in the central and northern parts of Northeast China, northeastern North China, central and eastern Inner Mongolia, and northern Xinjiang. Precipitation was higher in most parts of Northeast China, central and western North China, northern Xinjiang, and most parts of Inner Mongolia than in the normal year, but less in the central and eastern regions.

It is worth noting that the La Nina event is only one of the important underlying surface forcing factors that affect China's autumn and winter climate. Winter climate is also affected by factors such as Arctic sea ice and Eurasian snow cover . At the same time, the natural variability within the atmospheric circulation system also plays an important role.

Source: National Climate Center (Climate Change Center of China Meteorological Administration)

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