[Source: Jilin Provincial Meteorological Bureau]
On December 15, the temperature in our province began to fall under the influence of strong cold air, and on the 16th, the province opened the "quick freezing" mode, and the meteorological department successively issued a cold wave and severe cold warning. On the morning of the 18th, the minimum temperature in most parts of the province was lower than -23 °C, and the eastern mountainous areas were cold to "purple", and the minimum temperature dropped to -32 °C, and the lowest temperature in the province was -39.6 °C in Helong Baili. It is expected that this round of low temperature weather will last until the 22nd, and the temperature in the province will begin to rise from west to east on the 23rd, and the extreme low temperature period will come to an end.
How does such an extremely low temperature weather form?
Why is it colder in the southeast?
1
There is strong cold air activity. The public of the Northeast is interested in the "cold Siberian air" It is no stranger, because the Siberian region is the only way to cause the cold wave and severe cold weather in the Northeast, and the cold air is no exception, from the temperature distribution of about 5 kilometers (500hPa), it can be seen that the huge cold air mass from the polar region spreads from the northwest to the southeast through Siberia, and the front of the cold air advances to the south of the Yangtze River, and the center of the cold air mass is entrenched in the northeast for a long time, and the central intensity is also maintained below -40 °C for a long time, and there is a huge continental cold high pressure near the ground, which is the root cause of the low temperature weather。
Distribution of cold air at an altitude of 5 km
2
The Changbai Mountains block and cause cold air to accumulate. Under the control of this huge cold air mass, why is the ground temperature in various places very different, especially the temperature difference between the mountainous areas in the eastern part of our province is more than 10 °C compared with the plain area? This has a great relationship with the topography, at an altitude of about 1500 meters (850hPa) cold air is affected by the terrain blocking, there is an accumulation of cold air on the west side of the mountain range, the cold air accumulates, sinks, forms a cold pile in front of the mountain, and the temperature difference between the mountain and the plain is reflected.
2
Long-wave radiation cools down at night. In addition to the activity and accumulation of cold air, the cause of cold weather is radiative cooling at night. During the day, the air on the ground and in its vicinity warms up by absorbing the sun's short-wave radiation; At night, the air on the ground and in its vicinity cools due to long waves radiating outward. Radiative cooling is closely related to local meteorological conditions, topography and surface conditions. In terms of meteorological conditions, radiative cooling is particularly pronounced at night when it is clear, dry, light or quiet, and the temperature drops sharply;
High altitude (850hPa) at an altitude of about 500 meters (850 hPa) and topographic distribution
What is the difference between a Cold Wave Warning and a Severe Cold Warning?
What is the difference between the two warnings?
The answer is yes, and the difference is clear.
First of all, there is a difference in the basic concept. A cold wave can be interpreted as "cold air coming in like a tidal wave", and there is also a term for "cold surge", which indicates the rapid activity of strong cold air. Severe cold can be interpreted as "severe cold", which indicates the degree of cold that can cause a disaster.
Based on the differences in basic concepts, different early warning standards have been developed. In the current early warning signal standards in our province, the blue warning signal for cold wave is a 24-hour minimum temperature drop of more than or equal to 8 °C, and the severe cold blue warning signal lasts for 2 days with a minimum temperature lower than -32 °C. Therefore, the cold wave not only considers the intensity of the cold air relative to the current air temperature, but also the speed of the influence of the cold air, which belongs to the "dynamic cold", usually accompanied by rain, snow and strong winds, while the extreme cold indicates the absolute intensity of the cold air, and has a certain persistence, is "static cold", usually with clear skies and quiet winds.
We can also see that cold waves may occur in spring, autumn, winter and other seasons, while severe cold only belongs to winter.
Taking the temperature change process observed in Tonghua County as an example, the early morning of the 17th can be divided into two stages as the dividing line. The first stage is: from the morning of the 15th to the early morning of the 17th, the temperature dropped all the way, and even the solar radiation absorbed during the day could not stop the pace of the cold air temperature drop, the minimum temperature dropped by 19.3 °C, and the ground pressure on the contrary increased rapidly, indicating that the cold high pressure advanced rapidly from northwest to southeast; the second stage: after the early morning of the 17th, the temperature changed significantly, the temperature dropped rapidly after nightfall, and the temperature rose significantly after sunrise, and the maximum temperature and minimum temperature were relatively low, which was the low temperature and severe cold stage.
From the 15th to the 18th, the temperature (red) and air pressure (black) change curves in Tonghua County
Expert advice:
1
At present, the temperature continues to be low, and the demand for energy supply in various localities has increased significantly, so it is necessary to focus on the reserve and allocation of various types of energy to ensure the energy demand of industrial production and residents' lives; heating enterprises should strengthen heating efforts in a timely manner to ensure the living needs of residents; and at the same time, all kinds of enterprises should strengthen the maintenance of pipe network facilities to prevent all kinds of pipelines from freezing, plugging and bursting.
2
It is necessary to pay attention to the temperature of sheds and pens according to weather changes to prevent frostbite of vegetables and flowers in sheds and frostbite of poultry and livestock.
Source: Chen Changsheng, director of Jilin Provincial Meteorological Observatory
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