Regulation of synoptic circulation in regional PM2.5 transport for heavy
air pollution: study of 5-year observation over central China
Abstract
The importance of regional air pollutant transport modulated by
large-scale synoptic circulation has been poorly understood for air
pollution. In the present study of 5-year (2015-2019) observation, we
targeted the Twain-Hu Basin (THB), a region of heavy
PM2.5 pollution over central China to investigate the
regulation of synoptic circulation governing regional
PM2.5 transport for heavy air pollution. It was found
that regional transport of PM2.5 predominated 65.2% of
the heavy pollution events (HPEs) over the THB based on the statistics
of observational environment and meteorology. By employing the
FLEXPART-WRF model, the regional transport of PM2.5 from
upwind source areas in central and eastern China (CEC) to receptor
region in the THB was identified with three prominent pathways in the
northerly, northeasterly, and easterly directions respectively. Based on
T-mode principal component analysis in conjunction with the K-means
cluster method, it was recognized that three regional
PM2.5 transport pathways for the HPEs over central China
were determined respectively by three patterns of synoptic circulation
over CEC with 1) weak high air pressure to the north, 2) strong high air
pressure to the northeast, and 3) weak high air pressure to the east,
governing the cold air invasions southwards to the THB region in central
China with the large contributions of 76.0%, 56.7%, and 53.9% to the
THB- PM2.5 concentrations in the HPEs, revealing a
significant modulation of large-scale synoptic circulation for regional
transport of air pollutants in environmental change.