What are the causes and preventive measures of cold wave?
Cause of cold wave
China is located in the southeast of Eurasia, with Mongolia and Siberia in the north. Siberia has a cold climate, and northern Siberia is an extremely cold Arctic. The cold air that affects our country mainly comes from these areas. Strong cold air in polar and alpine areas intrudes along the westerly belt and northwest airflow and moves rapidly and explosively to the southeast, bringing strong cooling, strong winds and heavy snowfall to the areas along the way. When it reaches a certain standard, it is a cold wave.
Located in the Arctic and Siberia at high latitudes, the ground receives little solar radiation due to the oblique sunlight all the year round. In winter, the temperature in the Arctic Ocean is often below -20℃, and the lowest temperature can reach -70℃~-60℃. The monthly average temperature of 65438+ 10 is often lower than -40℃. Low temperature greatly increases the density of the atmosphere, and the air shrinks and sinks continuously, which increases the air pressure, thus forming a strong, deep and broad cold and high-pressure air mass. When this cold and high-pressure force is enhanced to a certain extent, it will flood into the territory of China where the southeast air pressure is relatively low, forming a cold wave. Every time a cold wave breaks out, the cold air in Siberia will be reduced, and the air pressure will also be reduced. But after a while, the cold air gathered again and piled up, gestating a new round of cold wave outbreak.
Preventive measures of cold wave
1, agricultural production. Do a good job in clearing ditches and draining water stains in the field to prevent the accumulated water from freezing and aggravate the freezing injury; Smoke, irrigate, cover and wrap before frost to reduce the harm of frost to crops; Strengthen agricultural facilities, greenhouses and animal husbandry pens.
2. transportation. When the wind is strong, airports and highways should be closed. Under special circumstances, passenger trains should also be stopped to prevent traffic accidents caused by strong winds. Clear the snow on the road, sprinkle salt and sand on the road, and install snow chains on the wheels. Install deicing equipment on the plane or simply fly around the freezing rain area.
3. Electricity and communications. Start the residents along the power transmission lines and communication lines to beat and scrape the raincoats on the lines and take support measures.
4. Daily life. (1) timely add clothes to keep warm, pay special attention to keep warm hands and face, so as to avoid frostbite. (2) close the doors and windows, strengthen the outdoor structure. (3) Beware of gas poisoning, especially for families that use coal stoves for heating. ④ Elderly and infirm people, especially people with cardiovascular diseases and asthma who are sensitive to temperature changes, should try not to go out. ⑤ Avoid roads covered with snow and ice when walking and driving outdoors, and pay attention to slippery roads.
Cold wave classification
The cold wave yearbook of China Institute of Meteorological Sciences divides the cold air process into four levels: national cold wave, regional cold wave, strong cold air and general cold air.
National cold wave
The decreasing process of daily average temperature is > 65438 00℃, and the absolute value of negative anomaly is >; There are at least 32 weather stations in the north (accounting for one third of the number of stations in the north) and at least 13 weather stations in the south (accounting for about one quarter of the number of stations in the south). Or the total number of north and south stations reaching the above impact intensity exceeds 40, and the total temperature drop in the process is >; 7℃, the absolute value of negative anomaly > When the number of main stations at 3℃ exceeds 90 (accounting for 60% of the total number of north-south stations), it is regarded as a "national cold wave".
Precautions:
Abnormality: Abnormality refers to the average distance, which refers to the deviation between the current situation and the annual average level. A positive value of abnormal temperature indicates warmer, and a negative value indicates colder.
Average temperature anomaly: the difference between a series of average temperatures (daily average temperature, monthly average temperature, etc.). ) and the total average temperature. The increase of the average temperature anomaly means that the difference increases, and the temperature in the corresponding time period is abnormal.
Regional cold wave
The decreasing process of daily average temperature is > 65438 00℃, and the absolute value of negative anomaly is >; When the number of stations at 5℃ exceeds 20, the total temperature decreases >; 7℃, when the absolute value of negative anomaly is greater than 3℃, if there are more than 40 stations in the north and south, it is regarded as a "regional cold wave".
A strong cold air flow
When the number of stations that also affect the intensity reaches more than half of the regional cold wave standard, it is regarded as "strong cold air".
General cold air
When the number of stations that also affect the intensity reaches more than half of the standard of strong cold air, or the daily average temperature drops >; 7℃, the number of main stations with negative anomaly absolute value > 3℃ exceeds 20; Or processes that fail to meet the above standards but cause certain disasters are regarded as "general cold air".