What is the geographical environment of Zunyi?

Zunyi City is located in the north of Guizhou Province. It is located in the nationally planned important area for the comprehensive development of the middle and upper reaches of the Yangtze River and the comprehensive development of the Central Guizhou Economic Zone. It is in the core area and main corridor of the Chengdu-Chongqing-Central Guizhou Economic Zone corridor. It is the bridgehead, main position and pioneer area of ??Guizhou-Chongqing cooperation. It is the southwest The region is an important transportation hub connecting north and south, connecting east and west, and connecting rivers and seas. The city stretches 247.5 kilometers from east to west and 232.5 kilometers from north to south. Zunyi City borders Tongren City (Guizhou Province), Qiandongnan Miao and Dong Autonomous Prefecture (Guizhou Province), and Qiannan Buyi and Miao Autonomous Prefecture (Guizhou Province) to the east, and borders Guiyang City (Guizhou Province) and Bijie City (Guizhou Province) to the south. , connected to Luzhou City (Sichuan Province) in the west and bordering on Chongqing City in the north. The central urban area is 144 kilometers south to the provincial capital Guiyang City and 239 kilometers north to Chongqing City. Zunyi City covers an area of ??30,780.73k㎡, accounting for 17.46% of the area of ??Guizhou Province.

Zunyi City is located in the slope area where the Yunnan-Guizhou Plateau transitions to the Hunan hills and the Sichuan Basin. The terrain is undulating and the landform types are complex. The altitude is generally between 800 and 1,300 meters, which is on the second level of the country's terrain. Zunyi City's flat areas and valley basins account for 6.57%, hills account for 28.35%, and mountains account for 65.08%. The Daloushan Mountains run across it from southwest to northeast, becoming a natural barrier and the watershed between the north and south water systems of the city. Geographically, Zunyi City is clearly divided into two large areas: Shannan is one of the main bodies of the Guizhou Plateau, with low and middle hills and mountains Mainly located in wide valley basins, generally cultivated land is relatively concentrated and contiguous, and the land utilization rate is high. It is the main producing area of ??grain and oil crops.

From the edge of the Wujiang Valley to the Dalou Mountains, three levels of platform are clearly visible: the lowest level is 1,000-1,200 meters above sea level, the middle level is 1,300-1,350 meters above sea level, and the highest level is 1,500-1,600 meters above sea level. The northern part of the mountain is dominated by Zhongshan Canyon, with high mountains and deep valleys, obvious vertical differences in the mountains, and relatively scattered cultivated land. The southern part accounts for 37.6% of the total area of ??Zunyi City, and the northern part accounts for 62.4%. The landform types in Zunyi City can be divided into three major categories according to their origin: melt erosion landform area, melt erosion structural landform area and erosion landform area. Among them, the dissolution and melting structural landforms (karst landforms) are the most widely distributed, accounting for about 75% of the land area of ??Zunyi City. The lowest altitude in Zunyi City is at the confluence of Xishui River and Chishui River at the junction of Chishui City and Hejiang County in Sichuan Province, with an altitude of 221 meters; the highest altitude is at Niujiao Village in Baizhiba Qingba Nature Reserve in Tongzi County, with an altitude of 2227 meters. , is the highest peak of the Dalou Mountains.

The Daloushan Mountains form the main framework of the city’s terrain. This mountain range starts from Bijie City in the west and extends to Sichuan Province in the northeast. It is not only the watershed of the Wujiang River system and the Chishui River, but also the boundary mountain between the Guizhou Plateau and the Sichuan Basin. Its section across the central part of the city presents an arc shape protruding to the southeast, with an altitude between 1,500 and 2,000 meters, and the relative height difference is mostly more than 500 meters. The famous Loushanguan Pass is located on the backbone of the main line of Dalou Mountain, with Xiaojianshan towering on the east and west sides. It is majestic. The ancients called this pass "ten thousand peaks reaching into the sky, with a straight line in the middle". It is very dangerous and has always been used by military strategists. A battleground. The pass is a canyon with an altitude of 1,226 meters and a height difference of 400 meters between the north and south. The Sichuan-Guizhou National Highway winds through the pass, and the Sichuan-Guizhou Railway and Chongzhou-Zun Expressway pass through tunnels in the belly of Lou Mountain.

With the Daloushan Mountains as the watershed, the rivers in Zunyi City are divided into three major water systems: Wujiang River, Chishui River and Qijiang River, all belonging to the Yangtze River Basin. The length of rivers with water flow in Zunyi City is 9148.5 kilometers, the river network density is 0.3 kilometers per square kilometer, and there are 416 rivers with a length of more than 10 kilometers or a rain collection area of ??more than 20 square kilometers. Among them, two main rivers (Wujiang River and Chishui River) are advantageous for navigation. The inland river navigation range is 441 kilometers and leads directly to the Yangtze River. There are 60 first-level tributaries, 168 second-level tributaries, 149 third-level tributaries, 33 fourth-level tributaries, and 4 fifth-level tributaries. The surface (river) runoff is 17.88 billion cubic meters, about 17% of the entire province of Guizhou, and the water production per square kilometer is 580,000 cubic meters, about twice the national average.

There are ***463 rivers more than 10 kilometers away from the mayor of Zunyi, all of which belong to the Yangtze River Basin. With Daloushan Mountains as the watershed, the north and south belong to the two major water systems of Wujiang District and the upper reaches of the Yangtze River. The upper reaches of the Yangtze River The main stream area includes the main stream of Chishui River and its main tributaries such as Niudu River, Tongzi River, Xishui River, etc. The Wujiang District includes Pianyan River, Xiangjiang River, Yuqing River, Furong River, etc. The average annual river runoff in Zunyi City is 17.88 billion cubic meters. The groundwater runoff is 4.225 billion cubic meters, and the annual power generation capacity of exploitable water energy resources is 20.5 billion kilowatt hours, and the per capita share is 1.85 times that of the country.

Zunyi City is particularly affected by the monsoon. Winter and spring are mostly affected by cold waves or cold air moving from the northern hemisphere. Winter winds are generally northeasterly or easterly. When Zunyi is affected by the northeast monsoon, the clouds are dense and low, and the cloud tops are radiated and cooled at night, often causing night rain. If the southerly airflow meets the northerly airflow at this time and merges with the northerly airflow between Sichuan and Guizhou, a Yangtze River shear line will often be formed at an altitude of 3,300 meters, or a Yunnan-Guizhou quasi-stationary front will be formed near the ground, and the rainy weather will become longer. . In mid-April, the southwest monsoon moves northward, the number of cloudy days decreases, the number of sunny and partly cloudy days increases, and the temperature rises significantly. Due to Zunyi's low latitude and strong sunlight, the temperature may rise to above 30°C for three days in a row.

As the summer monsoon (southwest airflow) moves northward and the water vapor swept from the Bay of Bengal and the Indian Ocean increases significantly, Zunyi enters the rainy season around April 16, and moderate to heavy rains often occur. When the summer monsoon moves to the Yangtze River Basin from May to June and meets the northerly airflow, plum rainy weather will form in the Yangtze River Basin. Zunyi City is located in the upper reaches of the Yangtze River, and it also experiences plum rainy weather with heavy rainfall and frequent rainfall. The summer monsoon continues to strengthen and the southwest airflow continues to push northward. Zunyi City is under the control of pure southwest monsoon. The plum rainy weather begins to end and enters a dry weather with continuous sunny days, high temperature and little rain. In mid-September, the summer monsoon gradually weakens and retreats southward, the winter monsoon gradually strengthens and moves southward, and continuous autumn rain begins to appear in Zunyi. Later, when the winter monsoon basically controls Zunyi, it will turn into low cloud and gloomy weather with a lot of light rain.

Zunyi City is located at low latitudes. The cold air from Siberia reaching Zunyi has greatly weakened its deformation. Therefore, in the coldest period of winter in January, the extreme minimum temperature was only -7.1℃ (January 30, 1977) , 0.2 degrees higher than Zhijiang at the same latitude. In summer, it is often affected by the southwest monsoon, and the extreme maximum temperature during the hottest period in history was only 38.7℃ (August 18, 1953), 1.7℃ lower than the 40.4℃ in neighboring Chongqing. The annual average temperature in Zunyi City is 15.1℃, which is 0.6℃ higher than that in Kunming City. Therefore, Zunyi City has no severe cold in winter and no scorching heat in summer. It has abundant rainfall and a pleasant climate.

Spring (March to May): Spring is warm and windy, with occasional late spring cold; the seasonal average temperature is around 15.3°C, and the total precipitation is close to 300mm. In spring, the temperature warms up earlier, and the number of sunny days increases. Generally, the first day of ≥10℃ stably passes in early April. However, the climate is extremely unstable, and late-spring cold often occurs from late March to early April. Due to the frequent intersection of warm and cold air, hail occasionally occurs in April and May, and in some years it can bring severe disasters. The rainy season usually starts in mid-to-late April.

Summer (June to August): Rainy in early summer, drought in midsummer, but hot but not cool; the seasonal average temperature is about 24.1℃, and the total precipitation is 400~500mm. The extreme maximum temperature occurs in late July, reaching 37.4°C, but there are only 1 to 5 days of high temperature weather ≥35°C every year. Summer is the season with the most rainfall throughout the year, especially early summer and June, which is the month with the most rainfall in the year. Heavy rainfall occurs, and severe floods occur in some years. Midsummer from July to August is often controlled by the western Pacific subtropical high pressure, and droughts often occur.

Autumn (September to November): The autumn temperature drops sharply, with autumn wind and continuous rain from time to time; the seasonal average temperature is about 16.1℃, and the total precipitation is 240~280mm. In autumn, due to the sharp southward retreat of the summer monsoon and the southward movement of the winter monsoon, rainfall significantly decreases, the temperature drops significantly, and the number of rainy days gradually increases. Autumn winds appear in early September, and continuous rain occurs in more than half of the years from mid-September to mid-October. Heavy rain also affects production in the "three autumns". The rainy season usually ends in mid-to-late October.

Winter (December to February): There is no severe cold in winter, with rain and little sunshine and sometimes freezing. The seasonal average temperature is about 5.5℃, and the total precipitation is 60~70mm. The extreme lowest temperature occurred in late January, reaching -7.1°C. In winter, due to frequent cold air activity, stationary fronts in Yunnan and Guizhou often form, resulting in rainy weather and little sunshine in our city. It is the season with the least radiation among all seasons in the year. The coldest period often occurs in January in midwinter, and is often accompanied by freezing.