Influence of the previous North Atlantic Oscillation (NAO) on the spring dust aerosols over North China
Influence of the previous North Atlantic Oscillation (NAO) on the spring dust aerosols over North China
复制标题
DOI：
10.5194/acp-23-6021-2023
复制
发表时间：
2023-06
影响因子：
6.3
通讯作者：
Yan Li;Falei Xu;Juan Feng;Mengying Du;Wenjun Song;C. Li;Wenjing Zhao
中科院分区：
文献类型：
--
作者：
Yan Li;Falei Xu;Juan Feng;Mengying Du;Wenjun Song;C. Li;Wenjing Zhao
抽象的。北大西洋涛动（NAO）已被证实与北方许多地区的天气气候密切相关，但其对我国沙尘天气形成的影响和机制却鲜有讨论。利用台站观测资料和多重再分析资料，发现非沙尘源区华北地区（30-40 ° N，105-120 ° E）春季沙尘气溶胶（DA）含量高，年际变化强，且与前冬NAO有显著相关。根据1980-2020年华北地区9次受前冬北大西洋涛动负位相影响显著的春季涡度事件，分析表明：在春季涡度事件爆发前，由于涡动动量（热量）的瞬变辐合，（辐散）在DA源区，对流层高层纬向风速增加，通过动量向下传输加强中低层的纬向风。同时，乌拉尔山附近存在瞬变的涡动动量（热量）辐散（辐合），有利于乌拉尔山脊的建立和维持，有利于气温平流和涡度平流的发展。温度平流和涡度平流的共同作用，使西伯利亚高压和蒙古气旋在近地面建立、加强并向南移动，引导高纬冷空气南下，有利于DAs向下游华北地区的抬升和输送。同时，上游瞬变涡动通量输送的变化可以引起华北地区能量和质量的辐散，导致沙尘暴期间风的减弱，有利于沙尘气溶胶的维持，促进沙尘暴的爆发。研究揭示了瞬变涡动通量输送对NAO负信号调制的华北沙尘天气异常的影响，加深了对我国沙尘天气形成机制的认识。
Abstract. The North Atlantic Oscillation (NAO) has been confirmed to be closely related to the weather and climate in many regions of the Northern Hemisphere; however, its effect and mechanism upon the formation of dust events (DEs) in China have rarely been discussed. By using the station observation dataset and multi-reanalysis datasets, it is found that the spring dust aerosols (DAs) in North China (30–40∘ N, 105–120∘ E), a non-dust source region, show high values with a strong interannual variability, and the spring DAs in North China are significantly correlated with the previous winter's NAO. According to the nine spring DEs affected significantly by the negative phase of the preceding winter's NAO in North China during 1980–2020, it is shown that before the outbreak of DEs, due to the transient eddy momentum (heat) convergence (divergence) over the DA source regions, the zonal wind speed increases in the upper-level troposphere, strengthening the zonal wind in the middle–lower levels through momentum downward transmission. Simultaneously, there is transient eddy momentum (heat) divergence (convergence) around the Ural Mountains, which is favorable for the establishment and maintenance of the Ural ridge, as well as the development of the air temperature and vorticity advections. The combined effects of temperature and vorticity advections result in the Siberian Highs and Mongolian cyclone to be established, strengthen, and move southward near the surface, guiding the cold air from high latitudes southward, and is favorable for the uplift and transmission of DAs to North China downstream. Simultaneously, the changes in upstream transient eddy flux transport can cause both energy and mass divergence in North China, resulting in diminishing winds during DEs, which would facilitate the maintenance of dust aerosols here and promote the outbreak of DEs. This study reveals the impact of transient eddy flux transport on the dusty weather anomalies modulated by the NAO negative signal in North China, which deepens the understanding of the formation mechanism of DEs in China.