Six branches of weather forecast

China has a vast territory, the northwest is located in the hinterland of Eurasia, the largest continent in the world, the southeast is close to the largest surface Pacific Ocean, and the southwest is the highest plateau in the world, the Qinghai-Tibet Plateau. This extremely complicated geographical condition makes China's climate have strong monsoon, continental and type diversity characteristics. Compared with other countries in the same latitude in the world, this feature of China's climate is very unique.

The monsoon climate is remarkable.

China is located in the southeast of Eurasia. Facing the vast ocean, the huge thermal difference between land and sea makes the characteristics of monsoon climate in China more obvious. The main performance is that the prevailing wind direction changes significantly in winter and summer, and with the advance and retreat of monsoon, the precipitation also changes obviously seasonally.

In winter, Chinese mainland is mainly controlled by polar continental air mass or denatured polar continental air mass. At the altitude of 80 ~ 90 E, most of them are high-pressure ridges, while the coastal altitude is often large troughs. The cold air behind the front ridge goes south continuously, which strengthens the cold high pressure on the ground (Mongolian high pressure), and the warm ocean is mostly controlled by low pressure. The airflow constantly flows from the high pressure area to the low pressure area, which makes the northwest wind, north wind and northeast wind prevail in the lower troposphere in winter in China. The polar continental cold high and its accompanying polar front or sub-cold front are the main weather control system in winter in China, and the weather and climate are characterized by less precipitation, low temperature and dryness. In particular, the cold wave or strong cold air weather process lasts for a long time and has a wide range of influence, and the accompanying strong wind and cooling are harmful to industrial and agricultural production.

In summer, most parts of Chinese mainland are controlled by tropical and subtropical marine air masses and tropical continental air masses. The altitude is a trough of low pressure at 70 ~ 80 east longitude, and the coastal area is a shallow ridge. The ground pressure system is occupied by the Mongolian low pressure in Eurasia, which cooperates with the high pressure in the ocean, making southwest wind, south wind and southeast wind prevail in the lower troposphere in summer in China. At this time, in addition to the polar cold air and its accompanying cold front, continental thermal depression, subtropical high, tropical depression, tropical cyclone and easterly wave have become the main systems affecting the weather in China. Weather and climate are characterized by high temperature, high humidity and rainy weather. This climatic feature of rain and heat in the same season provides good conditions for agricultural production in China. The combination of high temperature and abundant rainfall makes China a major rice producing area in the world. Rice planting in China can be as far north as Mohe River in Heilongjiang Province, which benefits from the climate characteristics of the same season of rain and heat. However, continuous heavy rain or local heavy rainfall in summer in China often causes large-scale or local serious floods. The violent storms carried by tropical cyclones have a great impact on fishery production and maritime traffic, even causing loss of life and property, and often cause windstorms and floods near landing sites (sometimes deep inland).

The arrival of summer monsoon is marked by the sudden increase of rainfall. Generally speaking, the summer monsoon rain belt appears in the northern part of the South China Sea in early May and moves to the coast of South China in mid-May. Then slowly push north and stop in South China in late May. It suddenly pushed northward in early June and reached the middle and lower reaches of the Yangtze River in mid-June, which was the beginning of the Meiyu period. Meiyu usually lasts until the beginning of July. Then, the summer monsoon affects the area north of Huaihe River. In late July, North China and Northeast China entered the peak of the annual rainy season, which lasted until early August. Since the middle and late August, the summer monsoon rain belt has rapidly withdrawn southward, and the rainfall in the whole country (except the areas affected by tropical cyclones in the southeast coast) has rapidly decreased. From mid-September of 10 to early October of 10, it stagnated in the central and eastern parts of Jianghuai, forming a relatively rainy belt. Due to the influence of topography, there are many autumn rains in West China, and it is also a rainy area. 65438+ 10 September, the weather in North China and Central China is mostly crisp in autumn. 5438+ 10 In the middle of June, the rain belt retreated to South China. Whether the rainy season starts and retreats normally in all parts of China is closely related to the advance and retreat time of the summer monsoon.

The interannual differences such as the arrival, retreat and maintenance time of summer monsoon determine the different summer precipitation conditions and the distribution of drought and flood areas in China. Statistics show that in the year with strong summer monsoon, the rain belt moves rapidly to the north, and it is rainy in the north. The rainy period in the middle and lower reaches of the Yangtze River is short, and the summer drought is serious. On the contrary, the rain belt in the middle and lower reaches of the Yangtze River is stagnant, with excessive rainfall and flooding, while drought occurs in the north, such as 1999. Therefore, the characteristics of monsoon climate, especially the abnormal changes of winter and summer monsoon, make China one of the countries with the most frequent meteorological disasters in the world. Drought, rainstorm, flood and chilling injury are the main meteorological disasters in China. According to the statistics of 1950 ~ 1999, the average area affected by drought, wind and hail, low temperature frost and other disasters in China is about 38 million hectares every year.

Climate types in China viewed from the classification of heat index.

China is located in the southeast of Eurasia, the largest land in the world, facing the Pacific Ocean, the largest ocean in the world, with complex terrain and vast territory. From Altun Mountain in the west to Wusuli River in the east, it spans 63 longitudes. It starts from Mohe River in the north and reaches Zengmu shoal in the South China Sea in the south, with a latitude difference of 49 degrees between north and south. Therefore, the climate in China is very complicated and diverse. In terms of heat, China spans equatorial belt, tropics, subtropics, temperate zones, mountains, plateaus and cold climate from south to north. 87% of the country's land area is temperate, subtropical and tropical.

China is located in the east of Asia and the west coast of the Pacific Ocean. The territory starts from Zengmu shoal in the south (near 4 north latitude) and reaches Heilongjiang near Mohe in the north (above 55 north latitude), with a distance of about 5,500 kilometers from north to south. It starts from Pamir Plateau in the west (near 73 east longitude) and reaches the intersection of Heilongjiang and Wusuli River in the east (above 0/35 east longitude/kloc-), with a distance of about 5,000 kilometers from east to west. The land area is about 9.6 million square kilometers, the coastline of the eastern and southern continents is more than10.8 million kilometers, and the area of inland and coastal waters is about 4.7 million square kilometers. China borders 14 countries, and eight countries are near the sea: North Korea in the northeast, Russia, Kazakhstan, Kyrgyzstan and Tajikistan in the northeast and northwest, Mongolia in the north, Afghanistan and Pakistan in the west, India, Nepal and Bhutan in the southwest and Myanmar, Laos and Vietnam in the south.

1) has a wide variety, covering almost all natural disasters in the world. Among all kinds of disasters, floods, droughts and earthquakes are the most harmful.

(2) The disasters have high frequency, high intensity and serious losses. China is known as "three-year-old hunger, six-year-old decline, twelve-year-old shortage". According to historical statistics, from 206 ~ 1949 BC to 2 155 BC, there were 1029 floods and 1056 droughts, almost every year, and 10 ~ 20 years caused a disaster that injured more than 10,000 people. In recent 40 years, there have been 75 droughts, 5.8 floods, 6.9 typhoons and 2.5 freezing disasters every year, all of which far exceed the world average frequency. In the past 40 years, the affected area of crops in typical years is 40 million to 47 million hectares, and the affected population is about 200 million. The number of deaths caused by various natural disasters ranges from thousands to tens of thousands, and the direct economic loss exceeds 50 billion yuan. During the four years from 1989 to 1992, the average annual loss was about 1/4 of the global average annual loss of $50 billion in the early 1990s.

(3) The spatial and temporal distribution is wide, and the regional combination of disasters is obvious. The spatial distribution and regional combination of natural disasters in China have a strong correlation with the regional differences of natural and socio-economic environment. As far as macro distribution is concerned, droughts that mostly occur in spring and autumn are mainly distributed in northwest China, Loess Plateau and North China. Rainstorms and floods that mostly occur in summer are mainly distributed in the vast eastern monsoon region and concentrated in seven major river basins; Forest fires are mainly distributed in northeast and southwest forest areas, mostly in winter and spring dry seasons; Earthquakes are mainly distributed in active tectonic zones in southwest, northwest and north China. Low temperature freezing injury and snow and ice disaster are particularly prominent in the high cold current area of Qinghai-Tibet; Typhoons and storm surges mostly occur in the southeast coastal areas. In the southwest of China, earthquakes and heavy rains will lead to landslides, collapses, mudslides and flash floods. The spatial distribution of natural disasters also presents certain constraints. For example, the change of monsoon intensity leads to the phenomenon of southern waterlogging and northern drought in an area, and the phenomenon of waterlogging before drought or drought before waterlogging occurs. According to the statistics of the National Meteorological Administration, the average frequency of meteorological disasters is increasing, with 19.56 in 1950s, 26.20 in 1960s and 28. 18 in 1980s.