1. Why does the northwest wind always blow in Xinjiang in winter (from Siberia)? 2. Why is it cooler in summer in Shanghai?

1。 In winter, a high pressure is formed in Siberia, so the northwest wind is formed because the air moves from the high pressure area to the low pressure area.

The average precipitation in Xinjiang is 145 mm, which is 23% of the national average annual precipitation of 630 mm. Not only is it lower than the national average, but it is also the least compared with other places in the same latitude on the earth. The distribution of precipitation is mainly influenced by atmospheric circulation and topography. Northwest wind prevails in Xinjiang, and the direction of water transport is from west to east. Topographically, the western part of southern Xinjiang is cut off by Pamir Plateau, and the western part of northern Xinjiang is low, so the precipitation from west to east decreases. One Happy and Fifth-200mm in the northern plain, 250-300mm in the western region, below 70mm in the southern Xinjiang plain, and only 7mm in Toksun. The precipitation in the plain area is of great significance to agriculture in northern Xinjiang. The precipitation in the plain area in summer can supply some crops with water, such as wheat from turning green to maturity. The water demand that precipitation can meet is 27% in Altay, 56% in Tacheng, 45% in Yili and 29% in Urumqi. In winter, the precipitation in northern Xinjiang accounts for 25% to 40% of the whole year, and the thickness of snow reaches 5-25 cm, which is not only beneficial to the growth of winter wheat, but also provides water for the winter wheat to turn green. The scarcity of precipitation in southern Xinjiang plain is of little significance to agricultural water supply, and the trace precipitation during crop emergence may also cause soil to return to alkali. There are many precipitation centers in mountainous areas of Xinjiang, with an annual precipitation of more than 400 mm, all of which are concentrated in mountainous areas. Tianshan Mountain is called a wet island in the desert. The annual precipitation in the mountainous area of northern Xinjiang is 400-600 mm. Individual windward slopes in Yili River Valley can reach 1000 mm. The annual precipitation above the southern slope of Tianshan Mountain is 300 to 500 mm. The annual precipitation on the northern slope of Kunlun Mountain is generally 200 to 300 mm, and the local windward slopes can reach 500 mm. In summer, precipitation in mountainous areas directly forms runoff and flows into rivers, which is the main water source for agricultural irrigation. 80% of farmland water in Xinjiang comes from rivers. The snow on the mountain in winter and the melted snow in the following spring become the main water sources of rivers in spring.

2。 It's not cold at night in Shanghai in summer now. If we insist on cooling, we can only say that due to the influence of maritime climate, the atmospheric airflow at night blows from the ocean to the land, so there will be some cooling effect.

Shanghai has a subtropical maritime monsoon climate. The main climatic characteristics are: warm in spring, hot in summer, cool in autumn and cold in winter, moderate annual rainfall and relatively even seasonal distribution. Generally speaking, the climate is mild and humid, with four distinct seasons.

The highest temperature in Shanghai is in July and August. In recent years, the summer in Shanghai is getting hotter and hotter, and the number of high temperature days exceeding 35℃ is about 10 days. 1Late October to early February (usually during the Spring Festival) is the coldest time in winter. Although there are not many days of sudden cold (usually lasting three days), the wet cold in the south of the Yangtze River is too much for northern Renye Fang, and the biting north wind often blows. Don't wear some heavy warm clothes, gloves, scarves and hats should be fully armed. There are not many days of snow, sometimes it doesn't snow all the year round. March to May is the best tourist season in full bloom in spring. What needs special reminder is that the rainy season is from mid-June to early July, both sunny and rainy. The rainfall of more than 20 days accounts for about 1/4 of the whole year, so it is not suitable to travel during this period. From the end of August to the middle of September, typhoons are frequent, and there are often downpours. You must take a sun umbrella to Shanghai during these two periods. Fortunately, the climate is hot at this time, and sunny days can also be used as sun protection.