Why is it dry?

Question 1: Why does it cause drought? Causes and countermeasures of drought.

Performance. In terms of natural factors, it is mainly accidental or periodic precipitation reduction, but in recent years, some human activities have also aggravated the imbalance between supply and demand of water. From the perspective of human factors, there are four main reasons for the drought caused by human activities:

1. The population has increased greatly, resulting in an increasing shortage of limited water resources.

2. Forest vegetation is destroyed by human beings, and the water storage function of plants is lost, resulting in the decrease of groundwater and soil moisture.

3. Human activities have caused a lot of water pollution and reduced the available water resources.

4. The serious waste of water resources in China, especially agricultural irrigation, leads to the shortage of water resources. Fortunately, human beings have already started to act. In China, population control, afforestation, pollution control and development of environmental protection industry have become basic national policies. As a big agricultural country, our backward irrigation methods are also changing to efficient and energy-saving irrigation methods.

Question 2: Why is there a drought? Monsoon climate The climate of an area controlled by the monsoon. The most important feature is that with the rotation of monsoon in a year, the seasonal variation of precipitation is obvious. East Asia, South Asia and Southeast Asia are two typical monsoon climate regions, but due to the differences in latitude and geographical location, monsoon climate also has its own characteristics. Macao belongs to the Asian monsoon, which dominates between the mainland and the ocean in winter and summer. The air pressure is different, the wind direction is opposite, the characteristics of the wind are different, and the weather is very different. From April to August every year, it is controlled by the ocean airflow, and the southeast and southwest winds prevail, which is the summer monsoon; 9. From 10 to February and March of the following year, under the control of continental airflow, north, northwest and northeast winds prevail, which is winter wind. Because the intensity and advance and retreat time of monsoon are different from year to year, monsoon climate is prone to natural disasters such as drought and flood last year and flood this year. Monsoon climate is a mixture of continental climate and maritime climate. Summer is affected by the warm and humid air current in the ocean, which is hot, humid and rainy, and the climate is maritime. In winter, affected by the dry and cold air currents in the mainland, the climate is cold, dry and rainy, which belongs to the continental climate. In monsoon climate, it is warm in summer and cold in winter. Therefore, the annual temperature is higher than that of the ocean. Generally speaking, the most Leng Yue appeared in June+10 in 5438, showing continental climate characteristics; The hottest month appears in July and August, and the temperature in autumn is higher than that in spring, which also shows the characteristics of maritime climate. For example, the annual temperature in Changsha is 24.6℃, the average temperature in Leng Yue is 4.7℃ in June+10, and the hottest month is July-August. From the monthly average, the average temperature in July is 29.3℃, and that in August is 28.7℃, only 0.6℃ higher than that in August. In fact, in the 30 years from 195 1 to 1980, the average temperature was higher in 1/3 years than in July. Taking Nanjing as an example, the annual variation is 26.0℃, the coldest in October is 65,438+/kloc-0, with an average of 2.0℃, and the hottest in July-August, with an average of 28.0℃ in July and 27.8℃ in August, totaling1951~1. In monsoon climate, it is wet and rainy in summer and dry and rainy in winter. For example, the annual precipitation in Changsha is 1.390mm, accounting for 71%from March to August; The annual precipitation in Nanjing is 1.03 1mm, accounting for 74% from April to September. Under the monsoon climate, the amount of precipitation and the time of rainy season depend entirely on the time and intensity of monsoon advance and retreat. The rainy season in Changsha is one month earlier than that in Nanjing. In northern China, the rainy season only lasts from June to August, even from July to August. The length of rainy season is related to the control of summer monsoon. In monsoon climate, rainfall is extremely unstable and varies greatly every year. In Changsha, the rainfall in rainy years is twice that in rainy years, three times that in Nanjing and five times that in Beijing. Therefore, in the monsoon climate, frequent floods and droughts are extremely unfavorable to people's production and life. The high temperature in monsoon climate is basically the same as that in rainy season, and the rain and heat are in the same period, which is very beneficial to the development of agriculture. Because the crops are growing vigorously, when water is most needed, the rainwater supply is sufficient. High temperature in the whole year and low temperature in winter can reduce pests and diseases to some extent. However, due to the seasonal and interannual changes of precipitation, floods and droughts often occur, which often lead to reduced agricultural production. Preventive measures: planting trees, repairing dams and building reservoirs. . .

Question 3: Why is there drought in Yunnan? The special geographical location, changeable climate and environmental influence and complex geological structure of our province are the three main natural factors that caused the drought in our province this year. 1 Yunnan is located in a special geographical position on the low latitude plateau, with an average elevation of about 2000 meters. It is located in the southeast of the Qinghai-Tibet Plateau, near the South China Sea and the Bay of Bengal. There is a monsoon climate and plateau topography, which is easy to form a "foehn effect". "Foehn effect" means that when humid air rises on windward slopes, water vapor condenses into rain, and when it reaches the top of the mountain, the air dries, and then sinks along leeward slopes, raising the temperature. At this time, the air becomes drier and hotter, especially because several mountains in the province are blocking the airflow, resulting in extremely low water content in the air, making it difficult to form effective rainfall. In addition, another important reason affecting the "extinction" of rain in our province is global warming and the increase of extreme weather conditions, especially the intensification of El Ni? o phenomenon in the Pacific Ocean. Since last autumn and winter, the atmospheric circulation in the Qinghai-Tibet Plateau has been obviously abnormal. A tenacious cold and high-pressure air mass is formed in the plateau area, and the pressure field strength blocks the warm and humid air flow from the Indian Ocean and the Bay of Bengal, while the cold air in the north is not easy to reach the hinterland of Yunnan-Guizhou Plateau in the southwest, and it is difficult for the cold and warm air flows to meet to form precipitation, so the precipitation is less. The complex geological structure of our province has become the internal cause of drought. There are many limestone and karst areas in Yunnan, and there are widespread problems such as the inability to store surface water and the low utilization rate of groundwater, and there is a situation that' water flows downwards and people worry about heights'. "。 Because the mountainous and semi-mountainous areas in our province account for 94%, the difference between the highest point and the lowest point is more than 6600 meters. The mountains are high and the valleys are deep, and the rainwater quickly collects in the rivers at the bottom of the valley along the terrain, which is difficult to use. In addition, the karst area of the whole province is 1 10000 square kilometers, accounting for 28% of the national territory. Most or all of the rainfall runoff in karst areas seeps into the ground, which makes it difficult to conserve surface vegetation, thus aggravating the drought in our province.

Question 4: Why are droughts in some coastal areas related to atmospheric circulation? Usually the place where it rains is the place where cold and warm air meet, and it is difficult to make rain with one-way airflow. Can you imagine that Antarctica is the driest continent in the world?

Question 5: Why is drought accompanied by pests? Drought will kill the natural enemies of pests, and pests have strong drought resistance, so ...

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