Main meteorological disasters in the middle and lower reaches of the Yangtze River

the middle and lower reaches of Changjiang River

This area includes Hunan, Hubei, Zhejiang, Jiangxi, Shanghai, Jiangsu and Anhui provinces to the south of Huaihe River. It is located in the middle of China and belongs to subtropical humid monsoon climate. Its climate is characterized by hot Leng Xia in winter, distinct seasons and abundant rainfall. Floods at the turn of spring and summer and droughts in summer and autumn are the main meteorological disasters, and low temperature and rainy weather in spring, "cold dew wind" in autumn, typhoons and hail can also cause certain harm.

(1) Waterlogging: This area is one of the most waterlogged areas in China. During spring and summer (May-July), especially during the rainy season from mid-June to early July, the rainfall is concentrated and heavy, and the continuous rainstorm and heavy rainstorm are the direct causes of waterlogging. There are many hills in this area, and sudden heavy rain produces a lot of runoff, which flows into lakes and rivers. If floods occur in the upper reaches at the same time, it is more likely to cause rivers and lakes to flood, destroy dikes, flood houses and farmland, and even threaten people's lives and property. The two lakes plain, Poyang Lake plain and Yangtze River Delta are the most frequently flooded areas.

In the past 30 years, there have been 25 years of different degrees of floods, including severe floods for 5 years (1954, 1962, 1968, 1969, 1980), with an average of 6 years. 1954 rainy season starts early, lasts long and has heavy rainfall. The Yangtze River has been flooded for a hundred years. 1980 witnessed a once-in-30-year flood, second only to 1954, and agricultural production also suffered huge losses.

(2) Drought: Drought can occur all year round, but there is plenty of rain in spring and early summer, and there is little drought, with a small scope and a light degree. Generally, the rainy season ends after July and is controlled by subtropical high. The weather is sunny and hot with little rain, and there is often drought in summer or autumn. At this time, it is the period when the growth water demand of middle rice and late rice is the largest. Severe drought will cause rice fields to crack and rice grains to turn yellow. Summer and autumn drought is the most harmful of all kinds of droughts, mostly concentrated in July-September. Severe drought areas mostly occur in Hunan, Hubei and Jiangxi provinces.

In the past 30 years, droughts of varying degrees have occurred almost every year. There are 9 years (1955, 1959, 196 1, 1963, 1966, 1967,/kloc-). The continuous drought in summer and autumn occurred for seventeen years, with the largest drought range of 1959, followed by 1966.

(3) Low temperature and rainy weather in spring: March and April are the early rice sowing and seedling raising seasons in the middle and lower reaches of the Yangtze River. At this time, cold and warm air alternate frequently. If the cold air goes south, there will often be low temperature and rainy weather, which will lead to the rot of early rice seedlings.

According to historical data, cold air activities in the middle and lower reaches of the Yangtze River are more frequent in March than in April. According to statistics, from March 2/KLOC-0 to April 20, there are 2-3 cold air activities every year on average, and 4 times in some years.

In recent 30 years, the meteorological conditions of early rice in the middle and lower reaches of the Yangtze River are very bad for six years (195 1, 1955, 1962, 1965, 1967,/kloc-0). 1969, 1970, 1972, 1980), all for 13 years, accounting for 43.3%. Therefore, it is very important to master the characteristics of weather and climate evolution, sow early rice in time and prevent rotten seedlings.

(4) Cold dew wind: The average date of the first day of "cold dew wind" (japonica rice type) is from late September to early June of/kloc-0, with the earliest date generally in the middle of September and the latest date generally in the middle of 10. The law of the first day of "cold dew wind" is generally early in the north and late in the south; Inland early, coastal late. The distribution characteristics of the total days of "cold dew wind" are gradually decreasing from north to south.

There are seven years in thirty years (1957, 1967, 197 1, 1972, 1974,1979,65439).

(5) Typhoon: In recent 30 years, typhoons landed in this area in July-June and 65438+ 10, but mainly in August. In recent 30 years, there have been 13 typhoons landing in this area, accounting for about 6% of the total number of typhoons landing in China. Among them, there were 8 in August, accounting for 62% of the total number of typhoons landing in this area; The earliest typhoon landed on July/KOOC-0/6 (Typhoon/KOOC-0/of/KOOC-0/959) and the latest typhoon landed on June 45+08 (Typhoon No.26 of/KOOC-0 19665438).

Typhoons mainly affect coastal areas, and violent storms often flood farmland, lodging crops and overturning fishing boats. However, the rainfall brought by typhoons going inland is often beneficial to alleviate or alleviate the summer and autumn drought in this area.

(6) Freezing injury: There is basically no freezing injury in autumn and less in spring. Freezing injury mainly occurs in winter. After winter, if affected by strong cold air, the cooling is often accompanied by snowfall, freezing rain and freezing injury, which is not only harmful to winter crops such as wheat, broad beans and rape, but also harmful to transportation, telecommunications and livestock.

Thirty years, 1955, 1956, 1964, 1967, 1969, 1972, 1973,/.

(7) Hail: Hail can occur all year round, but it mostly occurs in February-April, which mainly harms winter crops and spring crops.