Ningxia Meteorological Observatory issued yellow warning of sandstorm. What level does yellow represent?

According to experts from the Environmental Meteorological Center of China Meteorological Bureau, the overall temperature in northern China was obviously high in the early stage, with the highest temperature in some areas in the same period in history. At the same time, the overall precipitation in northern China is less, especially in Inner Mongolia and Inner Mongolia. The Mongolian cyclone developed gradually, and the ground high pressure gradually strengthened after the cyclone, resulting in a very large pressure gradient between high pressure and low pressure, which led to windy weather on the ground, which was beneficial to sand lifting and transportation. How did the yellow warning of sandstorm come from? When will the air quality improve?

Tianjin Meteorological Bureau issued the first yellow warning signal of sandstorm this year, reminding Tianjin that there will be sandstorms with visibility less than 1000 meters during the day. On the afternoon of June 5438+04, yellow gale warning signal on land and yellow gale warning signal on sea were issued to remind relevant units and personnel to get ready. Wang Ying, chief forecaster of Tianjin Meteorological Bureau, said that on the evening of March 14, due to the influence of the high-altitude trough system, there was light rain and sporadic light rain in the whole city. The maximum rainfall occurred in Jizhou District in the northern region, with the rainfall of 2. 1 mm. After the rain, the air was in a state of near saturation due to the high relative humidity.

At the same time, in the morning of 15, the weak convergence of the wind field led to heavy fog in the city. The visibility in most areas is less than 500m, and the short-term visibility in some stations is less than 200m, such as Jizhou District. The fog tends to weaken around 8 am, mainly because the relative humidity of the air is obviously weakened, but then there is dusty weather. From 9: 00 a.m., taking wuqing district as an example, from fog to dust, the visibility dropped again. Dust dust also affects Tianjin from 9: 00 and gradually affects the whole city from northwest to southeast.

Detected the lowest visibility of 533 meters in the urban area. So far, there are about 6 northerly winds and 8-9 gusts in this city. According to the monitoring of PM 10, as of the press release date, 13: 00 is the time point of the strongest concentration in the whole day, and the pollution degree is obvious. It is predicted that 15 night visibility and PM 10 concentration will be improved with the gradual weakening of wind. However, due to the sand blowing from the upstream sand source, satellite monitoring shows that there is still a large area of dust in the air. Considering the weakening of the wind at night, the deposition of dust still exists, and there will be floating dust at night. The overall air quality tends to improve during 16. There is a southeast wind in the afternoon, with a maximum of 12℃ and a minimum of 2℃.

Wang Ying said that the cause of sandstorm weather must meet several conditions. First, there must be upward dust in the sand source, and unstable factors will involve the dust in the sand source entering the air; Followed by transportation and precipitation. This process is influenced by cyclone after dust is sucked into the air in the sand source area. As the cyclone moves eastward, the northerly airflow behind it is directly transported to the south. From Inner Mongolia to northern Hebei and then to Tianjin, dusty weather appeared in all the passing areas.

According to Wang Ying, for Tianjin, sandstorms are basically in Inner Mongolia or Mongolia, and the two main obvious factors are the distance from sandstorms and the strength of wind. In this dusty weather, Tianjin is weaker than Beijing, northern Hebei and even Inner Mongolia. Basically, these two factors are very weak. Sandstorms occur every spring, but they are rare in Tianjin. The occurrence of this sandstorm is due to the best coordination of all the conditions that form the sandstorm.