Abstract:

Based on the data of air quality in cities in northeast China and the weather situation from 2014 to 2017, the changes in air pollution in Northeast China and the distribution characteristics of heavy pollution weather situation were analyzed. The results show that from 2015 to 2017, the annual average mass concentrations of PM_2.5 and PM₁₀ in Northeast China demonstrate a decreasing trend, and the annual average mass concentration of PM_2.5 decreases faster. The maximum value of PM_2.5 is about 90-100 μg·m^-3 in central Liaoning and Jilin provinces. The average annual mass concentration of SO₂ is about 50 μg·m^-3 in the western Liaoning province, while the maximum value of NO₂ is about 45 μg·m^-3 in the Shenyang-Changchun-Harbin area, and the maximum value of CO mass concentration is about 1.6 mg·m^-3 in the northeast coastal area. On the other hand, the average annual mass concentration of O₃ in Northeast China is increasing. The maximum value is about 100 μg·m^-3 in Dalian and Yingkou cities. The maximum values of PM_2.5, PM₁₀, and AQI in different areas all appear in winter. The maximum values of SO₂ mass concentration in winter appear in Shenyang city with 180 μg·m^-3. The maximum values of NO₂ and CO in winter appear in Harbin city with 80 μg·m^-3 and 1.8 mg·m^-3, respectively. The maximum value of O₃ is about 140-150 μg·m^-3 in summer in Shenyang city. The air quality with severe (200 μg·m^-3 ≤ PM_2.5 < 300μg·m^-3) and more severe (PM_2.5>300 μg·m^-3) pollution levels show the characteristics of a rapid decrease around Harbin city, and a slight increase in the central Liaoning province. The cities with moderate pollution (150 μg·m^-3 ≤ PM_2.5 < 200 μg·m^-3) days in descending order are Shenyang, Harbin, and Changchun, and with light pollution (100 μg·m^-3 ≤ PM_2.5 < 150 μg·m^-3) in descending order days are Shenyang, Changchun, and Harbin. The weather conditions causing heavy pollution in Northeast China can be divided into three types: high-pressure type, low-pressure type, and high in the north and low in the south type, with the proportion of 62%, 27%, and 11%, respectively. For the high-pressure type, the high-pressure ridge at 850 hPa moves east over Northeast China, and the near ground is in the south or weak high-pressure center. Sometimes in the north of Heilongjiang province or southwest of Liaoning province, a weak low pressure is continuously generated and rapidly moved eastward. For the low-pressure type, the low-pressure system at 850 hPa develops and moves eastward through Northeast China, and the near ground is in a weak high pressure after a low pressure. For the high in north and low in south type, the Northeast region is influenced by both North high pressure and South low pressure at 850 hPa and the near ground.

Key words: Northeast China, Heavy air pollution, Weather situation