Why is it so cold this winter

  Recently, cold air has come in frequently, and continuous low temperature weather has also appeared in most areas of central and eastern my country.

The new crown virus is more active in cold weather. At present, the topic of whether this year is "cold winter" or "warm winter" has attracted public attention. The reporter interviewed Song Lianchun, director of the National Climate Center, and other experts.

How cold is it? The lowest temperature in Beijing is -19.6℃

  Since the beginning of winter, there are indeed more low-temperature weather.

Take Beijing as an example. From December 1, 2020 to January 6, 2021, the city's average temperature is -5.2°C, which is 2.0°C lower than the normal temperature (-3.2°C) in the same period of the year.

  This year is even colder, with the lowest temperatures at many stations falling below the historical extreme.

The lowest temperatures of 20 national-level weather stations in Beijing are all below -18°C, and the lowest temperatures of 10 stations have fallen below their historical extremes in the same period in early January, including 6 in Shijingshan, Tongzhou, Shunyi, Changping, Xiayunling, and Shangdianzi. Each station fell below the historical extreme value since its establishment, and Huairou Station tied the historical extreme value since its establishment.

The lowest temperature at the Southern Suburb Observatory in Beijing was -19.6°C, which was the lowest since February 1966 (the lowest temperature on February 22, 1966 was -27.4°C).

  As far as the whole country is concerned, affected by strong cold air, large-scale strong winds and strong cooling weather will appear in the central and eastern regions of my country starting from January 6, 2021.

  A cold wave will also sweep the country.

Affected by the cold wave, the Shandong Peninsula and Dalian in Liaoning fell to moderate snow, with heavy local snow; Sichuan Basin, Guizhou, southern Hunan, central Jiangxi, western Zhejiang and other places snowed, and local snow fell 8-17 in Yibin, Luzhou, etc. Mm; freezing rain occurred in central and southern Guizhou, southeastern Hunan, and central Fujian.

  The temperature drop across the country is obvious: in southern Shaanxi, eastern Hubei, central and eastern Jiangnan, and central and eastern South China, the temperature dropped by 4~8℃, and the local temperature dropped by 9~10℃; the lowest temperature in Shanghai was -7.1℃, Nanjing -7.8℃, Hefei- 10.8℃, Wuhan -8.5℃, Hangzhou -6.4℃.

Why is it so cold

  From the statistics of the National Climate Center, compared with the same period in history, the frequency of cold air activity has not been much since this winter.

In December 2020, there were two cold air processes affecting my country, namely from December 13 to 15, 2020 (national type of strong cold air) and December 29, 2020 to January 1, 2021 (national type) Cold wave).

These two times are the nationwide cold air process, which has a large impact area and strong cold air intensity.

  So why is it so cold this year?

Song Lianchun, director of the National Climate Center, said that the most direct cause of the recent low temperature in a large area is that since December 2020, the Siberian high and the strong East Asian winter monsoon have caused the strong cold air brought by the strong northwest wind to frequently invade Beijing and North China. In the region, the extreme low temperature weather process that occurred this time was the result of the continuous low temperature caused by the cold wave weather process from December 28 to December 30, 2020. At the same time, the windy weather made the wind-cold superimposition effect obvious.

Is it "warm winter" or "cold winter"

  Is it cold winter this year?

Song Lianchun said that cold air activities will continue to be frequent in the near future, and the temperature in some areas will be low; according to the prediction of the National Climate Center, there will be cold air activities in my country in the later period, and the temperature in some areas may continue to be low.

But whether this winter is a "warm winter" or a "cold winter" is still uncertain.

  Song Lianchun said: "The phenomenon of continuous low temperature weather this winter is not too extreme in history, because the winter has not yet ended. It is expected that the temperature will gradually pick up in late January and become higher than normal. The temperature in most parts of the country will be close in February. The probability of being at the same time or higher throughout the year is relatively high, so it cannot be said that this winter is the coldest winter in recent years."

  Song Lianchun introduced that from the historical sequence of the national average winter temperature in the past few decades, my country has shown a warming trend as a whole, and since the 1980s, most winter temperatures have been higher than normal.

In the past ten years and the winters of 2010, 2011, and 2012, the winters were significantly colder than normal. The coldest was the winter of 2011; the national average temperature in the winter of 2017 and 2018 was basically close to the same period of normal years. In the past two years, northern my country The temperature in a large area was significantly lower than normal in the same period in the south.

  Song Lianchun said that in the non-linear system of global climate, "global warming" is not like a simple connection question, it can directly correspond to "warm winter", "cold winter" or "is it cold in a certain process" etc result.

The overall trend of global warming has not changed, but there will be cold and warm fluctuations on the interannual scale in this trend. The external forcing signals on the two interannual scales are a measure of the climate in the context of the overall trend of global warming. Interannual variability modulation, they will not fundamentally change the global warming trend, but will affect the winter temperature fluctuations in individual years.

  "Sometimes it is like looking at a pendulum clock. Monitoring cold or warm, like observing the swing of a pendulum. Global warming does not mean that all regions are the same. The Arctic region is one of the fastest warming regions in the world." Song Lianchun Said that the frequent occurrence of extreme cold events is a typical response to global warming.

In terms of long-term trends, climate warming has led to an increase in the frequency and intensity of extreme events.

It is hoped that the whole society will work together to increase awareness of climate risk prevention, strengthen prevention and response capabilities, and try to reduce losses caused by extreme events.

  Author: 本报记者袁 newspaper correspondent Wang Yu Fei