Seesaw haze pollution in North China modulated by the sub-seasonal variability of atmospheric circulation

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Zhang, Ge, Gao, Yang, Cai, Wenju, Leung, L. Ruby, Wang, Shuxiao, Zhao, Bin, Wang, Minghuai, Shan, Huayao, Yao, Xiaohong, Gao, Huiwang
• Language: unknown
• Published: 2023
• Subjects: 54 ENVIRONMENTAL SCIENCES; Arctic
• Online Access: http://www.osti.gov/servlets/purl/1496805; https://www.osti.gov/biblio/1496805; https://doi.org/10.5194/acp-19-565-2019

Utilizing a recent observational dataset of particulate matter with diameters less than 2.5 µ m (PM 2.5 ) in North China, this study reveals adistinct seesaw feature of abnormally high and low PM 2.5 concentrationsin the adjacent two months of December 2015 and January 2016, accompanied bydistinct meteorological modulations. The seesaw pattern is postulated to belinked to a super El Niño and the Arctic Oscillation (AO). During themature phase of El Niño in December 2015, the weakened East Asian wintermonsoon (EAWM) and the associated low-level southerly wind anomaly reducedplanetary boundary layer (PBL) height, favoring strong haze formation. Thiscirculation pattern was completely reversed in the following month, in partdue to a sudden phase change of the AO from positive to negative and thebeginning of a decay of the El Niño, which enhanced the southward shiftof the upper tropospheric jet from December to January relative toclimatology, leading to an enhanced EAWM and substantially lower hazeformation. This sub-seasonal change in circulation is also robustly found in1982–1983 and 1997–1998, implicative of a general physical mechanismdynamically linked to El Niño and the AO. Numerical experiments using theWeather Research and Forecasting (WRF) Community Multiscale Air Quality(CMAQ) model were used to test the modulation of the meteorologicalconditions on haze formation. With the same emission, simulations for threesuper El Niño periods (1983, 1997 and 2015) robustly show higherPM 2.5 concentrations under the mature phase of the super El Niño,but substantially lower PM 2.5 concentrations during the decay phase ofEl Niño (and the sudden AO phase change), further verifying themodulation effect of the sub-seasonal circulation anomaly on PM 2.5 concentrations in North China