Analysis of climatic conditions on the edge of the Yellow River?

The climate of the Yellow River basin belongs to the East Asian monsoon region, Lanzhou above belongs to the Qinghai-Tibet Plateau monsoon region, and the rest belongs to the temperate and subtropical monsoon regions. The seasonal characteristics are dry climate in spring, more wind and sand, and prone to spring drought; In summer, the subtropical high in the two Pacific Ocean moves northward, which causes warm and humid air to enter the Yellow River basin, and it is easy to produce precipitation when it meets the cold air in the northwest and south, which is the rainy season in the Yellow River basin. In autumn, the subtropical high in the western Pacific weakened and moved south, and the high-altitude westerly jet moved south, forming crisp autumn weather, but there were many persistent autumn rains over Weihe River and Lanzhou, such as the autumn rain in West China. In winter, the subtropical high in the western Pacific moves from south to east, and the northwest airflow prevails in the Yellow River basin, with frequent cold waves, less water vapor and significantly reduced precipitation.

Due to the vast territory of the Yellow River basin and numerous mountains, the height difference between the east and the west is very large, and the landforms in different regions are also very different. At the same time, the basin is located in the mid-latitude zone, and the situation affected by atmospheric circulation and monsoon circulation is more complicated. Therefore, the climate in different areas of the basin is significantly different, and the annual and seasonal changes of climate elements are great. The basin climate has the following main characteristics.

First, abundant sunshine and strong solar radiation.

The sunshine conditions in the Yellow River Basin are abundant in China, with the annual sunshine hours generally reaching 2000-3000h and the annual sunshine percentage mostly ranging from 50% to 75%, which is second only to the Qaidam Basin with the most sunshine, but generally about 1 times more than that in the Yangtze River Basin south of the Yellow River.

The total solar radiation in the Yellow River basin is at a moderate level in China, with the northern area of 37 ′ north latitude and the plateau area of east longitude103 ′ being 540 ~ 670 kJ/(cmz a). Most of the rest areas are 460-544 kJ/(cm' a), which is not as strong as southwest China, especially the Qinghai-Tibet Plateau, but generally larger than the northeast and south of the Yellow River, and is a strong radiation area in eastern China.

Second, the seasonal difference is large and the temperature difference is large.

There are great seasonal differences in the Yellow River basin. According to Zhang Jiacheng's research, the source above jiuzhi county in Qinghai Province is "winter all year round". The section from jiuzhi county to Lanzhou and the middle and upper reaches of Weihe River are "long winter without summer, and spring and autumn are connected"; The interval from Lanzhou to Longmen is "long in winter (six or seven months), short in summer (one or two months), and almost in spring and autumn"; The remaining basins are characterized by "Leng Xia fever in winter and distinct seasons".

The disparity in temperature difference is a major feature of the climate in the Yellow River Basin. The annual average temperature in the Yellow River basin decreases with the increase of height. The annual average temperature is 1 ~ 8℃ in the upstream, 8 ~ 14' in the midstream and 12 ~ 14' in the downstream. Generally speaking, with the three steps of the terrain, the temperature changes from cold to warm from west to east, and the east-west gradient of the temperature is obviously greater than the north-south gradient. The annual average temperature is around 4'C, and the lowest center is located in Heyuan.