China News Service, Beijing, October 10 (Reporter Chen Su) Recently, Beijing-Tianjin-Hebei and surrounding areas have encountered fog and haze weather. The Central Meteorological Observatory predicts that in the next three days, fog and haze will continue to develop. Why fog and haze are more likely to occur in autumn and winter, on October 31, meteorological experts interpreted this.
Since October 10, there has been a PM22.2 pollution process in Beijing-Tianjin-Hebei and surrounding areas, and on October 5, the pollution level in the central and southern Beijing-Tianjin-Hebei region and the northern part of Henan has reached moderate to severe levels. Beijing launched an orange alert for heavy air pollution from 10 o'clock on October 30 to 10 o'clock on November 30.
Liu Chao, a senior engineer at the Environmental Meteorological Office of the National Meteorological Center, said that quiet and stable weather is an important meteorological condition for fog and haze. Static weather can be formed when the wind speed in the horizontal direction is low and the atmospheric stratification in the vertical direction is stable. Under topographic factors, special terrain such as mountains, hills, and basins will hinder the circulation of air, resulting in low wind speed and less horizontal diffusion in the atmosphere. North China, the Sichuan Basin, the Huanghuai region, and the middle and lower reaches of the Yangtze River are all areas with frequent static and stable weather.
Talking about the reasons for the frequent occurrence of calm weather in autumn and winter, Liu Chao said that compared with summer, when there is no windy cooling weather in autumn and winter, the horizontal wind speed is smaller, and at the same time, the cloud cover is reduced in autumn and winter, and after losing the thermal insulation effect of the clouds, the surface radiation cooling will be very obvious at night, resulting in the temperature of the near-surface layer also decreased, forming a stable atmospheric stratification state in which the air temperature of the lower layer is lower than the temperature of the upper air. Therefore, it is easy to form a calm weather in autumn and winter. In addition, due to the radiation cooling effect at night in autumn and winter, water vapor is easy to condense, and the relative humidity near the ground will become larger, resulting in the growth of pollutant moisture absorption, which will accelerate the secondary transformation of pollutants, so the fog and haze weather in autumn and winter will be more serious.
Recently, there has been a rare warm heat in the same period of the year in the Huanghuai region in North China. According to the forecast of the meteorological department, before November 11, many places in the country continued to warm up, and the temperature was higher than that of the same period in normal years, especially in North China, Huanghuai and Jianghuai, and the temperature in many places was higher than 2 °C, and some areas will even experience rare warm heat in the same period of the year.
While warming, fog and haze weather in North China and other places will also continue to develop. The Central Meteorological Observatory predicts that from October 10 to November 31, the atmospheric diffusion conditions in central and southern North China will be poor, with light to moderate haze weather, including severe haze in central North China and other places. Since the night of November 11, under the influence of cold air, the atmospheric diffusion conditions in the above areas have gradually improved, and the haze weather has weakened and dissipated.
Liu Chao reminded that in calm and stable weather, air pollutants are easy to accumulate, so people with respiratory diseases and bronchitis and other diseases should minimize the time spent outdoors and wear masks when going out. In addition, the atmospheric visibility in calm weather is reduced, which can easily cause road congestion and traffic accidents, so it is important to be especially careful and pay attention to safety when traveling. (ENDS)