The winter of 2024 will be a not too cold winter for most of our country. According to the data of the National Climate Center, as of January 8, the temperature in most parts of China was 1 2 degrees higher than normal, and the temperature in Xinjiang and southwest China was 2 4 degrees. In the next 10 days, the temperature in most parts of China will still be 1 3 degrees higher than that of the same period in normal years, and the average temperature in some areas of Northwest China and western North China will be 4 6 degrees higher than that of normal years. In this way, the warm winter has begun to appear, and such a warm winter phenomenon has surprised and worried many people.
In January 2024, when many parts of China were warm, a very alarming stratospheric explosive warming event (SSW) occurred in the Arctic stratosphere. According to the monitoring data of the Arctic stratosphere, in just a few days, at an altitude of about 36,000 meters (10 hPa level), the Arctic stratosphere has warmed up by nearly 60 degrees Celsius, making the Arctic stratosphere, which has a temperature of about -80 degrees, close to -20 degrees, which is quite amazing. The occurrence of this SSW event has also attracted extensive attention and research from meteorological circles at home and abroad.
Sudden Stratosphere Warming (SSW) is a special meteorological concept, and the stratosphere is the second layer of the atmosphere, located above the troposphere at an altitude of about 10 50 km. The temperature of the stratosphere increases with altitude, which is the opposite of the troposphere which decreases with altitude. The temperature change in the stratosphere is mainly affected by solar radiation, so the temperature distribution in the stratosphere has a lot to do with the geographical latitude. In general, the stratosphere is warmer in the equatorial region and lower in the stratosphere in the polar regions. In winter, due to the lack of solar radiation in the polar regions, the temperature in the stratosphere drops below -80, creating a powerful cold-high-pressure system called the Polar vortex. The polar vortex is a persistent and large-scale cyclone that forms in the middle stratosphere, in the upper polar regions, and extends down into the troposphere. The presence of polar vortices affects the structure and intensity of airflow in the stratosphere and troposphere, which in turn affects the weather and climate in the middle and low latitudes.
Stratospheric explosive warming refers to a weather phenomenon in which the temperature of the polar stratosphere rises rapidly by tens of degrees in a few days. Before warming occurs, westerly winds in the stratospheric polar vortex slow down and then reverse. Explosive warming in the stratosphere has a huge impact on the structure and strength of airflow in the stratosphere, which affects the westerly belts and polar vortices in the lower layers. The occurrence of explosive warming in the stratosphere sometimes leads to the rupture or ** of the polar vortex, making the movement of cold air more complex and unstable, which in turn affects the weather and climate in the middle and low latitudes.
The mechanism of explosive warming in the stratosphere is not yet fully understood, but it is generally believed to be related to planetary fluctuations in the troposphere. Planetary fluctuations are large-scale airflow fluctuations that are affected by topography, temperature gradients, cyclones, and other factors, and can propagate upward from the troposphere to the stratosphere. When the energy of a planet's fluctuations is strong enough, it can have a destructive effect on the stratospheric polar vortex, causing explosive warming in the stratosphere. Stratospheric explosive warming is generally observed in the Northern Hemisphere and is not found in the Southern Hemisphere. This is because the terrain of the Southern Hemisphere is relatively flat, and the planetary fluctuations are weak enough to affect the stratospheric polar vortex.
What is the impact of explosive stratospheric warming on the weather and climate of our country?Generally speaking, the explosive warming of the stratosphere will lead to the positive anomaly of the stratospheric geopotential height to be transmitted to the troposphere, which will affect the pressure and wind fields of the troposphere, and thus affect the distribution and movement of weather systems. In general, explosive warming in the stratosphere leads to a weakening of the westerly wind belt, a polar vortex** or displacement, a cold wave moving southward, and lower temperatures in the middle and low latitudes.
However, this effect is not static, but is regulated and disturbed by a variety of factors, such as the type, intensity, duration, and frequency of explosive warming in the stratosphere, as well as the sea surface temperature, sea ice, cyclones, etc. in the troposphere. Therefore, the impact of stratospheric explosive warming on the weather and climate in China is a complex, nonlinear, and uncertain process, which requires more observations and simulations for in-depth study.
According to current research, the stratospheric explosive warming event in January 2024 is a polar vortex type SSW that caused two sub-vortices of the Arctic stratospheric polar vortex located over Eurasia and North America. This polar vortex** causes the geopotential height of the Arctic stratosphere to be anomalously transmitted down to the troposphere, thus affecting the pressure and wind fields in the troposphere.
Specifically, the weakening of the westerly wind belt in the troposphere and the warming event of the Arctic vortex** may continue to break southward, leading to a series of intense weather. For example, in the United States, the current forecast has pointed out that a strong cold wave in North America will move south on January 13, and parts of the United States will face a historic cold wave.
In Europe, the minimum temperature in Sweden and Finland has been below -40 degrees for many consecutive days, showing the activity of cold air in the Arctic.
So, what is the impact of this SSW event on the weather and climate in our country?In general, the effects of a stratospheric explosive warming event will be felt gradually in the weeks following the event and will continue into the spring, or even longer. The impact of stratospheric explosive warming events mainly affects the pressure and wind fields of the troposphere by changing the intensity and location of the Arctic vortex, thereby affecting the distribution of temperature and precipitation. The supercomputer forecast pointed out that in mid-January, the Arctic vortex will return to Siberia, and in the late middle of January, it will be very close to the northeast of China, which will lead to the severe cold in the northeast of China and other places to intensify again, but whether it will lead to the cold wave southward still needs to be further observed.