Ozone variability induced by synoptic weather patterns in warm seasons of 2014–2018 over the Yangtze River Delta region, China

• Published in: Atmospheric Chemistry and Physics
• Main Authors: D. Gao, M. Xie, J. Liu, T. Wang, C. Ma, H. Bai, X. Chen, M. Li, B. Zhuang, S. Li
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Pacific; aleutian low
• Online Access: https://doi.org/10.5194/acp-21-5847-2021; https://doaj.org/article/d845ad77fea7431480b5e6b754e44b77

Ozone (O 3 ) pollution is of great concern in the Yangtze River Delta (YRD) region of China, and the regional O 3 pollution is closely associated with dominant weather systems. With a focus on the warm seasons (April–September) from 2014 to 2018, we quantitatively analyze the characteristics of O 3 variations over the YRD, the impacts of large-scale and synoptic-scale circulations on the O 3 variations and the associated meteorological controlling factors, based on observed ground-level O 3 and meteorological data. Our analysis suggests an increasing trend of the regional mean O 3 concentration in the YRD at 1.8 ppb per year over 2014–2018. Spatially, the empirical orthogonal function analysis suggests the dominant mode accounting for 65.7 % variation in O 3 , implying that an increase in O 3 is the dominant tendency in the entire YRD region. Meteorology is estimated to increase the regional mean O 3 concentration by 3.1 ppb at most from 2014 to 2018. In particular, relative humidity (RH) plays the most important role in modulating the inter-annual O 3 variation, followed by solar radiation (SR) and low cloud cover (LCC). As atmospheric circulations can affect local meteorological factors and O 3 levels, we identify five dominant synoptic weather patterns (SWPs) in the warm seasons in the YRD using the t -mode principal component analysis classification. The typical weather systems of SWPs include the western Pacific Subtropical High (WPSH) under SWP1, a continental high and the Aleutian low under SWP2, an extratropical cyclone under SWP3, a southern low pressure and WPSH under SWP4 and the north China anticyclone under SWP5. The variations of the five SWPs are all favorable to the increase in O 3 concentrations over 2014–2018. However, crucial meteorological factors leading to increases in O 3 concentrations are different under different SWPs. These factors are identified as significant decreases in RH and increases in SR under SWP1, 4 and 5, significant decreases in RH, increases in SR and air temperature (T2) ...