• 关键词：降水  清除  初始浓度  雨强  PM_2.5  PM₁₀  合肥

• 基金项目：国家重点研发计划（No.2016YFC0201903，2016YFC0201902）；中央引导地方专项资金科技惠民项目（No.2016080802D116）；中国科学院科技服务网络计划（STS计划）-区域重点项目（No.KFJ-STS-QYZD-022）；安徽省淮河流域气象开放研究基金（No.HRM201506）；安徽省气象科技发展基金（No.KM201809）

• 于彩霞
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 邓学良
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 石春娥
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 吴必文
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 翟菁
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 杨关盈
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 霍彦峰
• 1. 安徽省气象科学研究所, 安徽省大气科学与卫星遥感重点实验室, 合肥 230031;2. 寿县国家气候观象台, 寿县 232200

• 摘要：对合肥2015-2017年的降水、风和PM_2.5、PM₁₀浓度观测数据统计研究发现，降水对PM_2.5、PM₁₀有一定的清除作用，尤其在秋冬季节.秋冬季节小雨、中雨分别导致PM_2.5和PM₁₀浓度降低23.1%、40.4%和32.0%、63.7%.雨日PM_2.5/PM₁₀比例上升8.4%，表明降水对PM₁₀清除作用更显著.降水前后PM_2.5浓度变化与降水前PM_2.5浓度、降水强度、降水时长密切相关.当降水强度大于4 mm·h^-1或PM_2.5初始浓度高于115 μg·m^-3时，降水对PM_2.5产生明显清除作用；而降水强度小于1 mm·h^-1或PM_2.5初始浓度低于115 μg·m^-3时由于吸湿增长作用极易造成PM_2.5浓度反弹升高；且持续3 h以上雨强介于1~4 mm·h^-1的降水也对PM_2.5产生清除作用.降水前后PM₁₀浓度变化与初始浓度密切相关，而与雨强相关性较弱.当PM₁₀初始浓度大于50 μg·m^-3，降水就对PM₁₀产生明显清除作用，且PM₁₀初始浓度越高，降水后PM₁₀浓度下降越多.风速大于2 m·s^-1可显著降低PM_2.5浓度，因此，当风速大于4 m·s^-1时合肥较少出现中度及以上污染，但易造成地面起尘，使PM₁₀浓度不降反升.合肥冬季严重污染主要出现在西北风向，夏季中度以上污染天气较少，主要出现在风速低于3 m·s^-1的东南风向.

• Abstract：The scavenging effects of rainfall and wind on PM_2.5 and PM₁₀ in Hefei were investigated using hourly data of ground level meteorological parameters and mass concentrations of PM_2.5 and PM₁₀ during 2015-2017. Statistical results show that rainfall played significant role on removing PM_2.5 and PM₁₀ in the air, especially in fall and winter. The light (moderate) rain decreased PM_2.5 concentration by 23.1% (40.4%) and PM₁₀ concentration by 32.0%(63.7%), respectively. Furthermore, the ratio of PM_2.5 to PM₁₀ increased by about 8.4% on rainy days, indicating that precipitation had a more significant effect on coarse particulate removal. The change of PM_2.5 concentration before and after precipitation was closely related to the initial concentration of PM_2.5, the intensity and duration of precipitation. When the precipitation intensity was greater than 4 mm·h^-1, or the initial concentration of PM_2.5 was higher than 115 μg·m^-3, the precipitation had a significant clearance effect on PM_2.5. However, when the precipitation intensity was weak (rainfall intensity< 1 mm·h^-1)or the initial concentration of PM_2.5 was lower than 115 μg·m^-3, the concentration of PM_2.5 would rebound and rise due to the increasing hygroscopic growth. When the rainfall intensity was between 1~4 mm·h^-1 and precipitation lasted for more than 3 hours, it also had a scavenging effect on PM_2.5 if PM_2.5 initial concentration was between 35 μg·m^-3 and 115 μg·m^-3. The change of PM₁₀ concentration before and after precipitation was closely related to the initial PM₁₀ concentration, but the correlation with rainfall intensity was weak. When the initial PM₁₀ concentration was greater than 50 μg·m^-3, it was obviously removed by precipitation, and the higher the initial PM₁₀ concentration, the more PM₁₀ concentration decreased after precipitation. The wind with a velocity over 2 m·s^-1 could weaken the concentration of PM_2.5 significantly, so the moderate or above pollution episode was rare when the wind speed exceeded 4 m·s^-1. However, strong wind caused dust on the ground, resulting in PM₁₀ concentration increase. Generally, heavy pollution events appeared primarily under northwest wind in winter and southeast wind with wind speed lower than 3 m·s^-1 in summer.

• Key words：rainfall  scavenging  initial concentration  rainfall intensity  PM_2.5  PM₁₀  Hefei

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