How many levels of cold wave warning are there?

The cold wave warning signal is divided into four levels, which are represented by blue, yellow, orange and red respectively.

1, cold wave blue warning signal

Standard: within 48 hours, the minimum temperature drops by more than 8℃, the minimum temperature is less than or equal to 4℃, and the average wind power on land reaches above 5. Or it has dropped by more than 8℃, the lowest temperature is less than or equal to 4℃, and the average wind power reaches more than 5, which may continue.

2, cold wave yellow warning signal

Standard: within 24 hours, the minimum temperature drops 10℃ or above, the minimum temperature is less than or equal to 4℃, and the average wind power on land can reach 6 or above. Or it has dropped above 10℃, the lowest temperature is less than or equal to 4℃, and the average wind force is above 6, and it may continue.

3, cold wave orange warning signal

Standard: within 24 hours, the minimum temperature drops 12℃ or above, the minimum temperature is less than or equal to 0℃, and the average wind power on land can reach above 6. Or it has dropped above 12℃, the lowest temperature is less than or equal to 0℃, and the average wind force is above 6, and it may continue.

4, cold wave red warning signal

Standard: within 24 hours, the minimum temperature drops 16℃ or above, the minimum temperature is less than or equal to 0℃, and the average wind power on land can reach 6 or above. Or it has dropped above 16℃, the lowest temperature is less than or equal to 0℃, and the average wind force is above 6, and it may continue.

Extended data

1, cold wave and strong wind

Cold wave gale is windy weather caused by cold wave weather. Cold wave and gale involve a wide range, including Inner Mongolia, Gansu, Ningxia, northwestern Shaanxi, northwestern Shanxi, Hebei, northern Henan, Heilongjiang, Jilin, Liaoning and other places in northern China, and cold wave and gale can also occur from the south of Huaihe River to the middle of South China Sea.

Cold waves and strong winds are mainly northerly winds, and the wind force is generally 5 ~ 6. When the cold air is strong or the ground low pressure develops strongly, the wind force can reach 7 ~ 8, and the instantaneous wind force will be even greater.

2. Cold wave freezing injury

An obvious feature of cold wave weather is severe cooling. Low temperature will lead to crop freezing, rivers and ports freezing, traffic interruption, and often bring economic losses to industry and agriculture. Cold wave freezing injury refers to the freezing injury of winter cold to overwintering crops. The cold wave weather process is a weather process in which a large range of strong cold air moves south in high latitudes, causing severe cooling and strong winds in its path.

When the temperature drops below 0℃ (freezing point) or remains below 0℃ for a long time, the plants of overwintering crops will be frozen and lose all physiological activities, leading to plant withering or death. Severe low temperature will also cause livestock to get sick or freeze to death, which will lead to serious meteorological disasters in agriculture and animal husbandry, that is, cold wave freezing injury.

Cold wave freezing injury is mainly caused by low temperature freezing injury to plant tissues below 0℃ (freezing point). Many research results show that the freezing of cells and tissues caused by low temperature is the cause of plant death.

3. Cold wave and snowstorm

During the cold wave, the most prominent weather is snowfall (rain), strong wind and severe cooling. Proper snow cover in winter is beneficial to crops overwintering, increasing soil moisture, freezing pest eggs and reducing air pollution. However, the snowfall caused by the cold wave is too large, and even snowstorms for several days or even longer will cause disasters.

In pastoral areas, due to the "white disaster" caused by cold wave and snowstorm, pasture is buried deep in snow, livestock can't eat fresh grass and hay can't be supplied, which leads to freezing hunger or illness, resulting in a large number of deaths, which is very harmful to animal husbandry.