Zigong geographical environment

Zigong's climate belongs to subtropical monsoon climate zone. The sunshine time is short, the four seasons are distinct and cloudy weather is common. The climate is warm, with annual average temperature 17.0- 18.0, extreme maximum temperature of 40, annual sunshine 1 150- 1200 hours. The frost-free period is 320-350 days. There is abundant rainfall, with an average annual precipitation of 1000- 1 100 mm.

It belongs to a typical basin climate with the characteristics of early spring, hot summer, cool autumn and warm winter. Zigong has a foggy climate and short sunshine time. The barking of Shu dogs to Japan in folk proverbs is an image description of this climate feature. The air in Zigong is very humid. Although the temperature is not high in summer, the average maximum temperature generally does not exceed 30 degrees Celsius, which often makes people feel sultry. The temperature is not low in winter, and the average monthly temperature is above 5 degrees Celsius. However, due to the influence of cloudy days and air tides, the rain in Zigong is concentrated in July and August, with a monthly rainfall of more than 200 mm and an average rainy day of 16- 18 days. In winter and spring, there is little rain and little snow and ice. Zigong's shallow hills are undulating, and the terrain is inclined from northwest to southeast. Generally, the altitude is between 250 and 500 meters, and the urban area is between 280 and 400 meters. The rivers in the city are mainly the Tuojiang River system, and the lower reaches of the Tuojiang River flow through the city boundary 127 km. Fuxi River is the main tributary of Tuojiang River in the city, with Xushui River and Weiyuan River in the upper reaches, with a total basin area of 3,490 square kilometers. To the west of the city, Yuexi River runs through Rongxian County from north to south, belonging to Minjiang River system.

The tectonic system of Zigong is Yangzihuai, Sichuan Taiao, Zhongchuan Taigong and Zigong Depression. It is adjacent to Weiyuan-Longnvsi platform dome in the north, Chishui depression in the southeast, Luzhou uplift in the south and Liangshan fold belt in the southwest. The structure of this area is simple and the distribution of rocks is gentle. The southeast is tightly folded and has a long and narrow structure; The northwest structure is relatively broad and gentle. The terrain is high in the northwest and low in the southeast. The northwest is the distribution area of low mountains in the city, and the elevation of mountains is generally 500 ~ 800 meters. The highest point is the main peak of Dingjiashan in Rong county, with an altitude of 90 1 m. The elevation in the southeast is generally about 300-400 meters, mostly 300 meters (50 meters), and the lowest point is on the surface of Tuojiang River, with an altitude of 24 1 meter. The maximum relative height difference is 66 1m, and the general terrain relative height difference is less than 50m.

The landform type belongs to low mountains and hills, which are composed of low mountains, hills, flat dams and river valleys. The low mountains are banded, distributed in the northwest and southeast, with a wide distribution area, criss-crossing valleys and interspersed among hills. The terrain is dominated by hills, and the flat dams are very narrow and scattered, generally terraces along the river and flat land between hills. The terrain is divided into low mountains, hills and flat dams. The low mountains are mainly distributed in 13 towns in the west of Zheng 'an, Bao Hua and Lijia in Rong County, and in Shuanggu, Changshan, East of Liu Jia, and Qingshanling and Longguan Mountain in Fushun County, accounting for about 17% of the total area of the city, with hills accounting for about 80% and flat dams accounting for only 3% of the total area of the city. In addition, there are various valleys, accounting for nearly 45% of the city's total area, which are divided into gullies, gullies, erosion gullies, karst valleys, basins and river valleys. The density of all kinds of valleys is 2.85 kilometers per square kilometer.