Geographical environment of Xunyang county

Xunyang is located in the northern edge of the subtropical zone, with a Qinling barrier, which blocks the cold air going south and the warm air flowing back to the Hanjiang River Valley. The territory has a warm and humid climate with four distinct seasons. From 1989 to 2009, the average temperature increased by 0.5℃, especially in autumn and winter. The number of days in summer increased by 23 days, and decreased by 7~ 12 days in spring and autumn. The average annual precipitation decreased by 90.6 mm.

From March to May in spring, the weather in spring is changeable and uneven, and cold air often invades, which makes the daily average temperature drop obviously. The average temperature dropped by 6℃ (or above) four times in 24 hours. There is less precipitation in spring, accounting for 22% of the annual precipitation. In dry years, droughts often occur before March. There is a saying that "Spring rain is as expensive as oil". It seldom rains in rainy years. The total sunshine hours are only more than those in autumn.

In summer, June to August, July and August are hot periods all year round. From mid-July to mid-August, the high temperature ≥35℃ lasts as many as 10 days, and the extreme maximum temperature is 43. 1℃. There is a lot of precipitation in summer, and the rainfall accounts for 5 1% of the annual total. Maximum precipitation of a rainstorm: June 1 17. 1mm, July 123. 1mm, August105.7mm. The summer drought is obvious from July to August, and the severe summer drought period can be as long as 55 days. The sunshine time in summer is longer than that in other seasons.

In autumn from September to June165438+1October, the temperature drops obviously, and the lowest temperature is below 0℃ as early as June165438+1October 14. September is the second peak month of annual precipitation, accounting for 24% of the total, and it is also a month with great changes in precipitation over the years. It is rainy in autumn. From September 30th to June 7th, 10 is a rainy period, which often leads to landslides. There are fewer sunny days in autumn, and the sunshine hours are reduced, and the total hours are slightly more than those in winter.

Winter lasts from 65438+February to February of the following year. Winter is the coldest period of the year. The lowest temperature in February 2,65438 was below 0℃, and it rose to above 0℃ on March 4 of the following year. The minimum temperature < 0℃ is 39 days. After winter, the snowfall gradually increases, and the snowfall period is 1 1.30 to March 1.8. The depth of snow is generally 2~4 cm, and the maximum thickness of snow is 14 cm. In the north and south mountain areas, the snowfall usually lasts from 10 to April of the following year, and the thickness of the snow can reach 30 cm, and the snow cannot melt for several months. Winter precipitation is small and unstable, which is prone to drought. The total sunshine hours in winter are the least in a year.

With the increase of topography, the temperature in the middle and high mountains in China decreases, the number of days in summer decreases and the number of days in winter increases. There is basically no summer in Yangshan Mountain at an altitude of 1700 meters, and the winter is as long as 223 days.