Freezing disaster

The temperature drops sharply in a short time, or the average temperature is abnormally low in a short time (1 ~ 3 months), resulting in human and animal casualties and economic losses. Can be divided into frostbite and frostbite.

(1) frostbite

1. Definition

Generally, it means that the surface layer temperature suddenly drops from above 0℃ to below 0℃, or the average minimum temperature in winter or early spring is lower than the average value of the same period for many years and lower than the lower limit of the low temperature of the affected body, resulting in animal and plant casualties and economic losses.

classify

According to the types of crops affected by the disaster, it can be divided into: freezing injury of winter wheat, etc.

According to weather phenomena: strong wind cooling, heavy snow, heavy rain, freezing rain, ice accumulation, etc.

3. Geographical distribution of freezing injury

1) The winter wheat areas in northern China-Huanghuaihai and Xinjiang-often cause large areas of wintering wheat to freeze to death and reduce production due to the invasion of strong cold air in1~ February.

2) Middle and lower reaches of the Yangtze River-southern Jiangsu, southern Anhui, Shanghai, Zhejiang, Jiangxi and Hunan. It mainly occurs from June 1 1 to March of the following year, and there are differences between different places in the morning and evening.

(2) Chilling injury

1. Definition

Generally speaking, crops suffer from environmental temperature lower than that required for their growth and development (but still above 0℃) during the growth period, which leads to delayed growth period of crops or impaired physiological function of reproductive organs, resulting in reduced agricultural production. classify

Due to the different crop types in different regions, the same crop has different requirements for temperature conditions in different growth periods, so the chilling injury is regional, and different regions have different names and categories.

The low-temperature seedling rot weather in early rice planting areas in the south of the Yangtze River in spring is called low-temperature chilling injury or late spring chilling injury.

In autumn, late rice in Guangdong, Guangxi and southern Fujian suffered from low temperature at heading and flowering stage, which reduced production, which was called cold dew wind.

During the growing period of crops, low temperature occurs continuously in Northeast China from June to September, which is called summer chilling injury in Northeast China.

3. Characteristics

Cold air from the polar regions and Siberia invaded our country, bringing about sharp cooling, cold wind, rain and snow, freezing and so on, causing freezing disasters. Its characteristics are: ① wide occurrence range: affected by strong cold air, it occurs in a large area at the same time. (2) Strong seasonality and timeliness: There are great seasonal differences in agricultural production in different regions of China, and the requirements for environmental temperature in different growth stages of the same crop are also different. Therefore, whether crops are affected or not depends largely on the season and duration of freezing disasters. (3) Strong regionality: China has a vast territory, the climate in different places is very poor, and the characteristics of agricultural activities and agricultural ecology are also very different. Therefore, the temperature indexes and categories affected by freezing disasters are also different. For example, the main hazards in Northeast China are the first frost and the low temperature in summer. The first frost is the most serious damage in North China and the eastern part of Northwest China, followed by the freezing damage of overwintering wheat. The middle and lower reaches of the Yangtze River are mainly caused by freezing injury in winter, snowstorm, cold in late spring and low temperature in autumn. South China has cold damage in spring, early rice rot, cold dew wind and freezing damage in winter. In Inner Mongolia, Qinghai-Tibet Plateau and Xinjiang pastoral areas, there are snowstorms and cold rains in spring. The wind (storm) that causes white hair in the northern pastoral areas will freeze the livestock to death; Yellow hair wind often carries a lot of dust, which makes the pasture degenerate and desertification; Causing black wind disasters (sandstorms) in arid areas, such as1May 5-6, 1993, black wind swept through Xinjiang, Gansu, Ningxia and other provinces (regions), 5.6 million mu of farmland was affected, 245,000 mu of orchards were affected, 85 people were killed, 3 1 person was missing, and 240,000 livestock died; Cold waves and strong winds can also subvert trains and ships. ④ The low temperature and freezing disaster will also destroy the lifeline of the town: transportation, water and electricity, gas and all kinds of equipment.

(3) Countermeasures for disaster reduction

1) Grasp the occurrence law of freezing disasters and arrange the agricultural layout reasonably. The freezing disaster has the greatest impact on agricultural production. Therefore, the meteorological department should accurately analyze and study the law, time and scope of local freezing weather, reasonably arrange the sowing and harvesting time of local crops, and avoid possible frost and chilling injury.

2) Improve the forecast and service level of freezing disasters. Preventing freezing disasters is a systematic project involving the whole society, which requires not only the meteorological department to accurately forecast and monitor the disaster weather and master the temporal and spatial laws of local freezing disasters, but also to inform local farmers as soon as possible so as to take effective preventive measures in time.

3) Improve agricultural technology and microclimate, and improve frost resistance. Such as industrialized rice seedling raising, membrane technology, windbreaks, etc. Effectively avoiding early rice seedling rot.