Weather and climate of winter months in Yan 'an over the years

Yan 'an belongs to a warm temperate semi-humid arid climate zone, and the annual climate change is controlled by monsoon circulation.

1. The annual sunshine is 24 18 hours, the sunshine percentage is 55%, the active accumulated temperature ≥0℃ is 3878. 1℃, and the average frost-free period is 162 days, with more than one crop and less than two crops a year.

2. Precipitation is mostly concentrated in summer, with heavy rainfall and high intensity, accounting for only 29% of the annual total from June 5438 to May of the following year. Drought and flood alternate, and spring drought is serious.

3. The average annual drought is 4.6 1 time, with a maximum of 6 times. The average annual drought period is 209 days, and the moderate-intensity drought accounts for 55%. 83% of the years have hail, accompanied by heavy rain and strong winds; 40% of the continuous rain occurred in the wheat field and autumn crop filling maturity. [8]

The four seasons in Yan 'an are spring from March to May, summer from June to August, autumn from 9- 10 165438+ 10, winter from 0/2 to February of the following year.

Spring is dry and rainy, the temperature rises rapidly, the climate is changeable, and there is strong wind and sand. Intraseasonal precipitation accounts for 65,438+07% of the annual total. The average temperature in March is 4.5℃, and the average temperature in May is 65438 06.9℃, and the highest temperature can reach 36.5℃. When strong cold air strikes, the minimum temperature can drop to about 0℃, resulting in frost.

It is hot and rainy in summer, and the seasonal precipitation is 3 12.3mm, accounting for 57% of the annual total. Mostly intermittent weather, sometimes accompanied by hail. The seasonal average monthly temperatures are 265,438+0.65,438+0 ~ 22.9℃, the hottest in July is 22.9℃, and the highest temperature in the season is 39.7℃, and there is no hot period. [8]

In autumn, the temperature drops rapidly, and it is wet, rainy and foggy. The precipitation days in September are 1 1 ~ 12 days, and the foggy days in September ~ 10 account for half of the whole year. The first frost appears from late September to early October of 10, and the soil freezes in early October of 10.

In winter, there is little rain and snow. It is clear in Wan Li, dry and cold, and Dorsey is north. The precipitation in this season is only 13mm, accounting for 4% of the annual total. 65438+ 10 is the coldest month, with an average temperature of -6.4℃, an extreme minimum temperature of -25.4℃ and an average relative temperature of 54-60%.