Why does Xi'an like to rain in September 2021?

Xi'an is a rather unique city. It has various cultural heritage and various delicacies and snacks, which are very popular among people. Recently, it has been raining all the time in Xi'an. This is a relatively normal phenomenon. It is mainly caused by the influence of subtropical high pressure, global warming and geographical location. 2021Why Xi'an likes to rain in September

1. Subtropical high pressure

In September, it rained in Xi'an for more than ten days. Judging from meteorological data over the years, it is normal for Xi'an to be rainy in September. In fact, the odds are relatively high over the next ten and a half days.

Xi'an has a warm temperate semi-humid continental monsoon climate, with moderate rainfall and four distinct seasons. The winter is cold, windy, foggy, with little rain and snow; the spring is warm, dry, windy, and changeable; the summer is hot and rainy, with prominent droughts, thunderstorms and strong winds; and the weather is cool in autumn. The annual precipitation ranges from 500 to 750mm, mainly in summer and autumn. Xi'an has been in the northwest of the subtropical high pressure for a long time in summer and autumn, and southwesterly and northeasterly winds prevail in winter.

Subtropical high pressure occupies the Pacific Ocean during the Northern Hemisphere winter. As the sun's direct point moves northward, the subtropical high pressure also gradually moves northward. The northwest edge of the subtropical high pressure easily combines with cold air to form precipitation. However, due to factors such as topography and the intensity of subtropical high pressure, spring precipitation is mainly concentrated in East and South China, which also leads to a peak rainfall in Xi'an around May. In summer, Xi'an is controlled by the subtropical high pressure, resulting in more short-term heavy rains (large precipitation and short duration). When autumn comes, the northwest edge of the subtropical high passes through Xi'an again as it retreats southward, causing continuous precipitation in Xi'an in September (large amounts and long duration).

2. Global warming

The impact of global warming is complex. At present, the overall manifestation of rainfall is the northward shift of the rainfall belt, but this northward shift is not just a translational shift. Its scale and scope are locally specific. For example, against the background of the gradual increase in global temperatures and the northward shift of rainfall belts, precipitation in Shaanxi Province gradually decreased from the 1990s to the beginning of the new century.

3. Geographical location

In fact, the Guanzhong Basin where Xi'an is located does not have a rich water system, and the water area is relatively small, making it difficult to form a large amount of local thermal convection. To the south of the basin is the Qinling Mountains, the highest mountain range in the east. For Sichuan, the southwesterly airflow of the northwest Pacific subtropical high transports warm and moist air from the Indian Ocean to the Sichuan Basin and encounters cold air in the northern Tibetan Plateau, forming a continuous autumn rain in western China in September and October. However, due to the existence of the Qinling Mountains, many warm and humid airflows form orographic rain in the process of climbing the south side of the Qinling Mountains, and it is difficult to enter the Guanzhong Basin, which directly leads to two completely different dry and wet climates in Guanzhong and Hanzhong. When is the rainy season in Xi'an?

The rainy season in Xi'an is July, August and September. Xi'an has two obvious precipitation peaks, respectively in July and September. The average annual precipitation in Xi'an is 558~750mm, increasing from north to south. It changes every year.

In September, southern China, that is, the area near the Tropic of Cancer, is far from cooling down. Warm air is still hovering there, waiting for the cold current from the depths of Eurasia (Russia, Siberia) to drive them away. .

Not only in southern China, but also in the subtropical regions of South Asia and the Middle East (scientific name is subtropical high pressure), they are also waiting for the same result. In addition, since the two subtropical highs are located along the coast, a large amount of water vapor is also transpiration, but due to the hot weather, not much water vapor condenses into rain.

From September to October, the subtropical high pressure moves southward and the rainband returns to western China. It is said that there will be rainy weather. This continuous autumn rain also has a scientific name, called "Autumn Rain in Western China" and "Autumn Rain" in Shaanxi. It is common in some areas of western China, usually appearing in Xi'an in September. Under the influence of the southern subtropical high, the weather generally lasts for about two to three weeks. How to dry clothes faster on rainy days

1. Paper towel press

After washing the clothes, no matter how hard you twist the clothes, there is always a lot of water on the clothes. You can use paper towels to iron your clothes. Paper towels are very absorbent. More paper towels can help dry the water out of your clothes.

2. Wring out the towel

We use a dry towel to help wring it out. First wrap the wet clothes in a dry towel and wring them firmly. At this time, the water on the clothes will be absorbed by the towel. It is best to choose towels that are highly absorbent.

3. Add a dry towel and shake well

We can also use a washing machine to dry. We can use the washing machine to dry once, and then put one or two dry towels on the second time, so that the clothes after shaking will be drier than usual.

4. Air dryer

If you want to wear it quickly after dehydration, you can only use a hair dryer to speed up drying. After using the pre-dehydration and towel-drying method, the clothes will only have 10% to 20% moisture at most. It only takes a little over ten minutes to dry your clothes with a hair dryer.