2016—2019年夏半年成都市区臭氧污染天气特征分析

为揭示成都市区臭氧污染气象条件特征，通过欧盟COST733天气客观分型软件对成都市区2016-2019年夏半年(5-9月)海平面气压场和500 hPa位势高度场进行大气环流形势分型，并结合同期臭氧监测数据、地面气象观测数据以及总云量实况分析产品，分析成都市区夏半年臭氧超标天气及气象要素特征.结果表明:成都市区2016-2019年夏半年共出现臭氧超标日数为159 d，超标率为26.0%，超标日主要集中于5-8月，小时超标多出现于14:00-17:00.臭氧污染日数最多的海平面气压场为弱低压型，其后依次为低压前部型、低压型、高压后部型.臭氧超标率最高的海平面气压场为低压前部型，其后依次为弱低压型、低压型、高压后部型.500 hPa位势高度场平直西风气流型臭氧超标日数最多，青藏高压型臭氧超标日数最少.青藏高压型是臭氧超标率最高的500 hPa位势高度场型，平直西风气流型臭氧超标率最低.成都市区臭氧超标日多出现在偏西北风下，近地面气象要素特征一般表现为风速1.2~1.6 m/s，气温在25℃以上，相对湿度多集中在70%左右，总云量和降水概率多低于60%，降水量级以小雨为主，太阳辐射和日照时数分别位于20.5~23.2 MJ/m2和6.0~7.8 h区间.小时臭氧超标近地面气象要素特征为气温和总辐射曝辐量相对较高，二者分别在30~36℃和0~3.5 MJ/m2之间，相对湿度在60%以下，总云量低于40%，以偏南风影响为主.研究显示，成都市区海平面气压场为低压型，500 hPa位势高度场为青藏高压型时，易发生臭氧污染. 

Characteristics of Ozone Weather in Chengdu during Summer of 2016-2019

This study analyzed the weather with excess ozone and meteorological elements in downtown Chengdu during the summer of 2016 to 2019. The meteorological characteristics of O₃ pollution were investigated through several complementary parameters, including ozone monitoring data, ground meteorological observation data, and actual total cloud cover product data. In addition, the atmospheric circulation of the sea level pressure field and the 500 hPa geopotential height field were classified using the COST733 software. There were 159 high-ozone days with the exceeding rate of 26.0%. The O₃ exceeding standard periods were mainly from May to August, and the high-ozone time was mainly from 14:00 to 17:00. The sea level pressure field for the highest ozone days was weak low pressure type, followed by low pressure front, low pressure, and high pressure back type. The sea level pressure field with the highest ozone exceeding standard rate was the low pressure front type, followed by weak low pressure, low pressure, and high pressure back type. The high-ozone days were mostly distributed in the 500 hPa potential height field with the straight westerly air type, and less distributed in the Qinghai-Tibet high pressure type. The 500 hPa potential height field type of the Qinghai-Tibet high pressure exhibited the highest O₃ exceeding standard rate. In contrast, the flat westerly airflow type exhibited the lowest O₃ exceeding standard rate. The high-ozone days occurred mostly under the westerly north wind. The near-ground meteorological elements generally included wind speed of 1.2-1.6 m/s, temperature above 25℃, and relative humidity at about 70%. During the high-ozone days, most of the total cloud cover and precipitation probability were less than 60%, and the precipitation was mainly light rain. The sun radiation and sunshine time were between 20.5-23.2 MJ/m2, and 6.0-7.8 h, respectively. The high-ozone hours were mainly influenced by southerly wind with temperature of 30-36℃. The relative humidity was below 60%, the total cloud cover was below 40%, and the sun radiation was 0-3.5 MJ/m2. The results indicate that ozone pollution in Chengdu is more likely to occur when sea level pressure field is of low pressure type, and the geopotential height field of 500 hPa is of the Qinghai-Tibet high pressure type.