Northern China experienced large scale temperature drop and precipitation

13-10-2017Source:China Meteorological News Press

Since the late September 2017, West China has seen persistent cloudy and rainy weather. Hence, the precipitation in northern Chongqing, Shaanxi, Hubei and Henan was more than normal years and even three to four times more in some of the above regions. Besides, affected by upland water and rainfall, it was appeared to be distinct autumn flood over Han River basin recently, bringing about higher water levels than previous years over the main stream of the middle and lower reaches of the Yangtze River basin, Dongting Lake and Poyang Lake.

From October 8, the cold air started from Xinjiang with the flow direction moving from western to eastern China and northern to southern China. In this process, eastern Northwest China, Inner Mongolia, North China, central-southern Northeastern China as well as Huang-Huai River basin and the south of the Yangtze River basin experienced strong wind and drop in temperature with rainfall and snowfall in some regions afterwards.

From the perspective of temperature change, over 6℃ drop in temperature was undergone over the North China, eastern Northwest China, Inner Mongolia and central-southern Northeast China with even more than 10℃ temperature drop in some regions. For instance, the temperature of Nanchang was 33℃ before the cold air and went down to 20℃ afterward. the minimum temperature of some portions in Xinjiang like Urumchi, Tianchi and others was even down to below 0℃.

The precipitation process caused by this cold air was mainly appeared in the northern China including central-southern North China, northeastern Sichuan, southern and eastern Shaanxi, southern Liaoning, northern Chongqing along with western and southern Huang-Huai River basin. Furthermore, the first winter snowfall happened in Urumchi on October 6, about one-week earlier than former years. Whereafter, Inner Mongolia, Gansu, Ningxia and Hebei experience the first winter snowfall as well.

According to Ms. Zhang Fanghua, Chief Forecaster of the National Meteorological Center of China Meteorological Administration (CMA), this cold air process lasts for a long period and has a wide-range impact, resulting in sharp temperature drop and plentiful rainfall in the northern China. “It is extremely uncommon to see heavy rainfall and even rainstorm over the North China in autumn”, she said.

When considering the reason, it is because that the location of the subtropical high was northward and its intensity was considerably powerful, the warm-wet airflow alongside the north of the subtropical high was strong, yet the cold air spreads to South China during the movement. Hence, the confluence of cold and warm air caused this large-scale and long-time precipitation process.

Editor: Chen Meiqi