Long-term variation of satellite-based PM2.5 and influence factors over East China

With the explosive economic development of China over the past few decades, air pollution has attracted increasing global concern. Using satellite-based PM2.5 data from 2000 to 2015, we found that the available emissions of atmospheric compositions show similar yearly variation trends to PM2.5, even if the synchronization is not met for each composition, implying that the intensity of anthropogenic emissions dominates the temporal variation of PM2.5 in East China. Empirical orthogonal function analysis demonstrates that the dominant variability in the seasonal PM2.5 is closely associated with climate circulation transformation, incarnated as the specific climate index such as the Asia Polar Vortex intensity in spring, the Northern Hemisphere Subtropical High Ridge Position for the leading mode and the Kuroshio Current SST for the second mode in summer, the Asia Polar Vortex Area for the leading mode and the Pacific Polar Vortex Intensity for the second mode in autumn, the NINO A SSTA for the leading mode and the Pacific Decadal Oscillation for the second mode in winter. Therefore, apart from anthropogenic emissions effects, our results also provide robust evidence that over the past 16 years the climate factor has played a significant role in modulating PM2.5 in eastern China.


This file includes
Supplementary definition S1-S7 and Supplementary Figs. S1-S7, which can be classified as follows: S1: The APVI is defined as the total mass of air in the isohypsic surface between 500 hPa isostatic surface and polar vortex south bound characteristic isohypsic surface over the 60°E-150°E of the Northern Hemisphere, and can be calculated as Where  atmospheric density, R the radius of the earth, and  and  are the difference of latitude and longitude of the adjacent grid on the monthly average geopotential height of 500 hPa, with the grid interval in 10 degrees and 5 degrees, respectively. 0 is the geopotential height of the polar vortex south bound characteristic isohypsic surface, and Hij is the geopotential height on the northern grids of the polar vortex south bound characteristic isohypsic surface. R 2 can be considered as a constant of 0.1.

S2:
The Western North Pacific Typhoon number is the number of tropical cyclones with a maximum surface wind over 8 grade that generate or enter near the center of the Pacific and south China sea, at the north of the equator and west of the date line. NHSHRP represents the average latitude of the location of the subtropical high ridge center on 500 hPa at each meridian in the region of 10°N-60°N and 5°E-360°. The center can be identified by the conditions of zonal wind u=0 and y u   >0. PNA, defined as the time coefficient of PC2 of the 500 hPa geopotential height field in the region of 20°N-90°N and 0-360°, is one of the main circulation structures in the northern hemisphere mid-latitude region, and the most significant modal to indicate the circulation change in the middle and upper troposphere. It describes the atmospheric circulation anomalies in the north Pacific and North America region.
S4: APVA, defined as the sector area of the 500 hPa geopotential height field in the north region of the polar vortex southern boundary isohypse line between 60°E and 150°E, can be calculated as Where the unit of S is 10 5 km 2 , 2 and 1 are the longitude in radians,  the latitude of the polar vortex southern boundary, and R the earth radius (6378 km).

S5:
The PPVI is defined as the total mass of air in the isohypsic surface between the 500 hPa isostatic surface and the polar vortex south bound characteristic isohypsic surface over the 150°E-120°W of the Northern Hemisphere. The EATI can be calculated by the sum minus the maximum and plus the minimum of 500 hPa geopotential height on the trough-line in the range of 30°N-55°N and 110°E-170°E.

S6:
The CAA is the amount of cold air process, which meets a continuous temperature decreasing more than 5℃ in three days at some designated meteorological stations. The NINO A SSTA Index is the regional average of SSTA in the range of 25°N-35°N and 130°E-150°E.

S7:
The PDO is defined as the PC1 time coefficient of SSTA north of 20°N in the Pacific region.
The PPVA is defined as the sector area of the 500 hPa geopotential height field in the north region of the polar vortex southern boundary isohypse line between 150°E and 120°W.