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夏季欧亚中高纬地区高频和低频ISO对华北地区地面臭氧浓度影响的对比分析

Comparative Analysis of the Effects of High-frequency and Low-frequency ISO in Mid-High Latitude Eurasia on Surface Ozone Concentration over North China during boreal summer

  • 摘要: 本文基于1979–2022年ERA-5再分析资料,对比分析了夏季(5–9月)欧亚中高纬地区两类(高频10–30天和低频30–60天)大气季节内振荡(ISO)的时空演变特,并基于中国环境监测总站发布的每日最高8小时平均臭氧浓度(MDA8 O3)资料,对比分析了两类ISO对我国华北地区地面臭氧浓度的影响。研究结果表明,高频(10–30天)ISO的发生频率要明显高于低频(30–60天)ISO,同时高频ISO的强度也要大于低频ISO。高频ISO的传播特点为随位相由欧亚中高纬地区较为匀速的向东南方向传播;而低频ISO则会在西伯利亚地区加深发展并停滞较长时间,之后才会随位相向南传播并减弱。二者在垂直结构上都呈准正压结构。波活动通量的结果表明Rossby波能东南传播有利于温度异常东南传播,随着高频和低频ISO地面温度异常向南传播到华北地区,对当地的天气气候条件产生影响。地表臭氧浓度异常随位相分布表明,高频与低频ISO在传播过程中都会通过调节降水、相对湿度和总云量的异常,进而影响温度异常来影响华北地区的地表臭氧浓度。由于两类ISO的影响范围略有不同,造成相应的地表臭氧污染异常的区域略有不同。以上结果表明了两类ISO的传播均会对地面臭氧浓度造成影响,为华北地区的污染防治提供了指示。

     

    Abstract: This study, based on ERA-5 reanalysis data, contrasts the spatiotemporal evolution characteristics of two types (10-30 days and 30-60 days) of intra-seasonal oscillations (ISO) in mid-high latitude Eurasia during boreal summer. Meanwhile, using the daily maximum 8-hour average ozone concentration published by the China National Environmental Monitoring Center to analyse the influence of HF-ISO and LF-ISO on surface ozone pollution in North China. The results indicate that the occurrence frequency of HF-ISO is higher than LF-ISO, and the intensity of HF-ISO is also stronger than LF-ISO. HF-ISO will propagate southeast from the mid-high latitude Eurasia by phase in a constant speed. While the LF-ISO tends to intensify and linger in the Siberian region for an extended period before propagating southward. Both ISOs exhibit a quasi-barotropic structure. The results of wave flux show that the southeast propagation of Rossby wave energy is conducive to the southeast propagation of temperature anomalies. As SAT anomalies spread southward to North China, they affect local weather conditions. The distribution of ozone concentration anomalies suggest that two types of ISOs can modulate precipitation, relative humidity, and total cloud cover, consequently affecting temperature anomalies to influence surface ozone concentration. Because of the slightly different geographical influences for two types of ISOs, the corresponding surface ozone pollution anomalies are different. These results indicate both ISOs can influence surface ozone concentration, which provide valuable insights for pollution control efforts for North China.

     

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