First, what are the main characteristics of the summer climate? In the summer, due to the influence of the tropical air masses, the southerly wind is generally blowing, bringing about abundant precipitation. In May and June, it was the peak rainfall period in most of Guangzhou and Guangdong provinces in the first flood season. In August, it was the peak rainfall period in the late flood season. During these months, the highest number of rainstorms occurred. At the same time, from June to October each year, the tropical cyclones landed and affected. More than 89% of the main time periods in the province and Guangzhou were within this period. According to statistics from 1949-2000, an average of 7-8 tropical cyclones affected Guangdong each year, of which 3.9 landed in Guangdong, accounting for 40% of the number of tropical cyclones landing in China. The hottest month of the year was July. The average July temperature in Guangzhou was 28.3-28.7 degrees. The extreme maximum temperature had appeared at 37.5-38.7 degrees. Shaoguan in northern Guangdong had appeared at 42 degrees. The extreme maximum temperature in Guangzhou since 1951-2000 was 38.7 degrees, which occurred on August 12, 1953. Second, in the summer when the high temperature heat damage occurs? According to the statistics of historical meteorological data, July is the month with the highest average temperature in the year. For example, in northern Guangdong, it is 29.2 degrees in Shaoguan, 28.3 degrees in Guangzhou in Guangdong, and 28.9 degrees in Zhanjiang in southwestern Guangdong; August is the second highest average temperature in the year. In the month, if Shaoguan was 28.7 degrees, both Guangzhou and Zhanjiang were 28.3 degrees. The extreme maximum temperatures in July and August were all above 37 degrees, of which Shaoguan had appeared at 42 degrees in August 1953, Meixian County had 39.5 degrees in 1971 and July 1989, and it was prone to appear in July and August. High-temperature heat damage is particularly prominent in the years when tropical cyclones are less active and weaker. Third, how is the geographical distribution of high-temperature heat damage in summer? The main features are: First, heat damage North heavy south light; Second, high temperature days inland more than coastal. For example, in July and August, the average daily temperature is ≥ 29 degrees, the average annual number of days in Shaoguan, Guangdong is 31 days, in Qinghai, Guangdong Province is 29 days, and in Haifeng, Shantou, Yangjiang, and Xuwen along the coast is 11-17 days; The average number of days for air temperature ≥ 30 degrees is 16 days for Shaoguan, 13 days for Qingcheng, and 1-5 days for Haifeng, Shantou, Yangjiang and Xuwen along the coast. Fourth, the supply of vegetables in autumn season, the climatic analysis of statistical data shows that, in August and September each year, the average daily vegetable market is significantly lower than the annual average, so in August and September is the main period of the autumn season. The reasons for the formation of the climate in the off-season are as follows: 1. The rainstorm is the main cause of the autumn season. Summer and autumn are the end of spring sowing vegetables and the autumn sowing of vegetables. The area of ​​listed vegetables is already smaller. In case of unfavorable climatic conditions such as rain and sunshine, typhoon, rainstorm, etc., the damage will be severe and the amount of listing will be even less. July-September was the peak season of typhoon rains in Guangdong Province and Guangzhou City. The rainfall was concentrated and the intensity was high. At this time, the frequency of rainstorms was generally the same as the frequency of food shortages in August and September. Heavy rain and heavy rain in summer and autumn are not only easy to cause damage and dampness, but also reduce soil permeability, affecting the growth of vegetable roots, especially the showers after high temperature, and after sunny days, the heat of vaporization of soil moisture is easy to make. Leaf scald will also cause the fruit and vegetables of the eggplant to fall and fall, and the melon bean and leafy vegetables will rot. The output will be drastically reduced. If the seedlings meet with heavy rain at the beginning of sowing, the seeds will be washed into the ditch or be buried in the soil, resulting in seedling deficiency; if the seedlings have just been excavated soon, the root system will not stabilize, and once the rainstorm is hit, it will easily cause the roots to be exposed. Exposure to wilting death is very harmful. Heavy rain has little harm to vegetable production. The first is that seed and seedlings are hit by heavy rain, resulting in mechanical damage to seedlings, dead seedlings, raindrops, soil pulling, and soil hypoxia, affecting the growth of vegetable roots and plants; The second is lack of light, affecting the accumulation of photosynthetic products, resulting in plant growth is not strong; Third, high temperature, high humidity induced various pests and diseases, resulting in reduced production. 2, the impact of high temperature is the basic reason for the emergence of autumn season except for a few heat-resistant varieties, such as melon, pumpkin, melon, beans, and vegetables, most other vegetable varieties are not high temperature. Guangdong and Guangzhou are located at low latitudes and have strong solar radiation. Not only the extreme maximum temperatures are generally higher than 35-39 degrees, but also the high temperature season. The average temperatures in May and September all exceed 25 degrees. For most of the thermophilic vegetables, especially It is a cold weather vegetable is a non-season period. In July and August, the monthly average temperature is as high as 28 degrees Celsius; the daily maximum temperature is more than 35 degrees. It is common from late June to early September. Therefore, during the summer season, not only winter cold vegetables can grow, but also warm vegetables such as tomato and sweet. Peppers, etc. should not be planted, even if the heat of vegetables, such as small mustard, leeks and vegetables, long-term high temperature, especially high night temperatures will also appear accelerated aging, fiber, poor quality, low yield; In addition, high temperature and rain Both drought and high temperature will lead to multiple diseases and insect pests, which will increase the occurrence of the off-season. 3. The impact of tropical cyclones aggravated the huge wind power of the tropical cyclones during the autumn season. Not only did it blow down the sheds, causing mechanical damage to the vegetables and falling fruits and vegetables; tropical cyclones caused heavy rain and drowned seedlings; after tropical cyclones, they were injured. And flooded vegetables are also susceptible to diseases. Therefore, after the tropical cyclone, the market volume of vegetables will drop sharply. In summary, the impact of high-temperature storms on vegetable production is roughly threefold. First, seedlings and seedlings are vulnerable to torrential rain and seedlings and dead seedlings; heavy rain flushes the soil, causing water loss and soil compaction, and roots lack oxygen and have poor growth potential. The second is that the soil temperature is too high. At noon on sunny days in summer, the temperature of the topsoil of vegetable fields often exceeds 40-50 degrees, and frequent heavy rains not only cause vegetables to suffer heat damage, but also cause various types of diseases and insect pests. Third, under high temperature intensity at noon in the summer, the leaves are in a state of wilting and photosynthesis cannot be performed normally, resulting in low utilization of light energy and burning of plants, thus seriously affecting the growth and development of vegetables and the formation of yield. 4. Countermeasures and measures to solve the supply of autumn vegetables: Measures to introduce and cultivate good varieties of heat and rain resistance; develop protective cultivation in over-summer days; establish high-altitude summer production bases for low-altitude crossings; store vegetables in season to supplement off-season supply during peak seasons; Remedy etc. Measures: Increase the area of ​​mussels, expand the area of ​​vegetables with high resistance to heat and rain, and order large-scale contracts for storage of melon and other storage-resistant vegetables in other places; vigorously promote the use of appropriate technologies to raise the level of scientific vegetables; do a good job in the construction of water conservancy projects. Improve disaster prevention and reduction capabilities.
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