Multi-scale correlations between air quality and meteorology in the Guangdong−Hong Kong−Macau Greater Bay Area of China during 2015-2017

A multi-scale correlation analysis method is introduced and a combined analysis of multi-scale correlations between air quality and meteorology in Guangdong-Hong Kong-Macao Greater Bay Area (GHMGBA) of China is performed using 3-yr daily series of particulate matter (PM) fractions and O3 observations and collocated meteorological reanalysis data during 2015-2017. PM and O3 have significant seasonal oscillation and oscillations of 2-3 days, 5-7 days, quasi two weeks, and 20-30 days, which are typical periods in east-west wind (U), north-south wind (V), wind speed (WS), temperature (T), relative humidity (RH), 925-hPa specific humidity (Q), and surface air pressure (SP), although different types of meteorological parameters have different significant periods. In GHMGBA, the East Asian Monsoon has different significant impacts on PM and O3. The relationships of air quality with meteorology on higher frequency modes are usually very different from those on lower frequency modes since different mechanisms make effects. Correlation details may also differ on different synoptic scales. Especially, PM has consistent significant negative correlations with V, T, RH, and Q on seasonal oscillation but has large positive (negative) correlations with V, T, and Q (WS and SP) on oscillations of 2-3 days, 5-7 days, and quasi two weeks in winter half year. The latter synoptic correlations reflect the impact of the typical quasi-stationary front and cold front activities on PM, which usually includes two sequential asymmetric processes: a long no-precipitation stagnation period when ventilation, dilution, and hygroscopic growth make effects; and a short precipitation period when ventilation, dilution, and wet deposition make effects. In a word, local synoptic scales correlations cannot be directly extended to estimate the response of air quality to climate change projections.