The largest snowfall this year is determined, covering an area of more than 1 million square kilometers! Analysis: Be wary of follow-up effects

On the afternoon of October 6, as can be seen from the 24-hour temperature change map, the extensive blue-green cooling zone has been extended to the south of the Yellow River, which means that cold air has taken effect in more provinces. While the autumn rains in central and southwest China are continuing today, the temperature in Chongqing, Hubei, Henan, Shaanxi and other provinces and cities is low, and there is already a strong autumn mood, which is 10.6 degrees Celsius in Xi'anjinghe, 15.5 degrees in Chengdu Wenjiang, 16.2 degrees in Nanjing, 17.8 degrees in Chongqing Shapingba in the provincial capital-level cities, and even the lowest temperature in Nanchang south of the Yangtze River is only 20.3 degrees and Fuzhou is 20.5 degrees, both the lowest since August. As the cold air moves south, many places in the south of the mainland have officially begun the autumn process.

First, the maximum snowfall this year is determined

In fact, the southward movement of cold air in the past two days not only brought strong winds, cooling, wet and cool autumn rain, but also brought flying snowflakes to some areas - on the mainland's Qinghai-Tibet Plateau, these two days of cold air invaded the Qinghai-Tibet Plateau, just happened to meet the warm and humid air flow over the Himalayas to climb the Qinghai-Tibet Plateau, the collision of cold and warm masses suddenly caused a wide range of rain and snow, Qinghai, Tibet many places snowflakes, some netizens shot videos show that some parts of Qinghai have been snowed white, white winter scene.

According to the latest forecast from the Central Meteorological Observatory, the first widespread snowfall since the second half of this year has been determined and will affect much of the mainland's Qinghai-Tibet Plateau. Forecasts show moderate to heavy rain in parts of the eastern Qinghai-Tibet Plateau, Sichuan, central and western Yunnan and light to moderate snow at high altitudes from October 10 to 12. For example, on the forecast map on October 10, it can be seen that when the autumn rains in the central and eastern regions of the mainland subside, a wide range of snowfall will cover Xinjiang, Qinghai, Tibet, and some parts of southern Qinghai may even have heavy snowfall, which is expected to cover an area of more than 1 million square kilometers! This is a rare large-scale snowfall in the early winter of the Qinghai-Tibet Plateau, which will have a significant impact on agriculture, animal husbandry, transportation, energy and other aspects in the region.

After that, the forecast map on October 11 shows that widespread rain and snow will shrink to the east, and Qinghai and Tibet will also see a wide range of heavy snow, and in some areas even up to the level of heavy snow. In addition, some high-altitude areas in western Sichuan and Gansu are likely to have more snow, so this is a widespread rain and snow in the western region, and the range will be the largest since the second half of this year.

Second, the area exceeds 1 million square kilometers

First, let's take a look at the causes of this snowfall. According to supercomputer predictions, the snowfall was triggered by the formation of a low vortex on the Tibetan Plateau. Around October 10, a strong low-vortex system will form on the Tibetan Plateau and gradually move eastward, and as the low-vortex forms, it will attract cold air from the north and south and warm and humid air currents from South Asia to meet on the mainland Qinghai-Tibet Plateau.

Cold air is emitted from the Siberian high-pressure center, which has a strong sinking movement and cooling effect, causing the ground temperature to drop rapidly. The warm and humid air flow is emitted from the humid and hot Indian Ocean, which has a strong upward movement and humidification effect, which increases the water vapor content in the air. When two currents of different nature meet in the Qinghai-Tibet Plateau region of the mainland, they can stimulate a large number of convective clouds and produce a strong precipitation process. Due to the high altitude in the plateau area, the near-surface temperature will be close to or below the degree, so the precipitation in many places is mainly snow or sleet.

Second, let's take a look at the characteristics of this snowfall. According to the weather forecast, this snowfall will develop from October 10 and last until October 12, during which it will affect Xinjiang, Tibet, Qinghai, the western Sichuan Plateau and parts of southern Gansu in the western part of the mainland, and is expected to cover an area of more than 1 million square kilometers, accounting for more than 1/10 of the total land area of the mainland.

In terms of snowfall, according to the forecast of the Central Meteorological Observatory, Qinghai and Tibet provinces and regions will be the center of snowfall, and some areas may even experience heavy snowfall and local heavy snowfall. For example, in Zaduo in Qinghai Province, the official forecast shows that sleet will begin to appear in Zaduo on October 10, and then it will increase further to heavy snowfall. In terms of cooling magnitude, it is expected that the average temperature in the areas affected by snowfall will drop significantly, for example, after a blizzard, the minimum temperature will drop to about -5 degrees.

Third, be wary of follow-up effects

Finally, let's look at the after-effects of this snowfall. According to historical experience and expert analysis, this snowfall has both advantages and disadvantages for the mainland's Qinghai-Tibet Plateau. The upside is that the snowfall can increase soil moisture and groundwater reserves, and improve the decline in water resources in parts of the Tibetan Plateau. For example, the precipitation forecast of the Central Meteorological Observatory pointed out that in the next 10 days, one of the places with the most precipitation on the mainland is the western region, and the precipitation in the Qinghai-Tibet Plateau and southwest China is generally 25~100 mm.

The disadvantage is that this snowfall will also adversely affect transportation, energy, communications, etc., causing certain losses and difficulties. For example, snowfall can cause roads to freeze, accumulate snow, slide, increase the risk of traffic accidents, and affect traffic safety and efficiency; Snowfall can also cause power lines to freeze and break, affecting power supply and stability. Due to the low temperatures brought about by snowfall, it will also adversely affect agriculture and animal husbandry. The temperature forecast of the Central Meteorological Observatory shows that in Qinghai, western Sichuan and other places affected by snowfall, the temperature of the next 10 weather is significantly low.

On the one hand, it means that the heat in the northern hemisphere has begun to weaken, the South Asian high has begun to withdraw from the Qinghai-Tibet Plateau, the south branch westerly wind is about to form again, and the circulation pattern of the continent has begun to shift further to the autumn and winter pattern. On the other hand, the Tibetan Plateau is the "roof of the world", and the snow accumulation here can reflect sunlight and reduce heat accumulation, which in turn affects the climate pattern of the Asian region and is an important influence factor of winter weather. Therefore, this rare and widespread snowfall will rapidly increase the snow cover on the plateau and will also profoundly affect the weather patterns in the rest of the continent this winter, requiring continuous observation and response to possible weather events.