资源环境科技发展态势分析平台

Atmospheric waves have a broad spectrum of momentum at various frequencies and link to the PM(2.5)concentrations in northern China. We show that the meaningful circulations depended on the wave frequency and the rank of the PM(2.5)concentrations. The winter 2013-2019 PM(2.5)had different correlations with the subseasonal 850 hPa height anomalies at low (>30 days), intermediate (10-30 days), and high (<10 days) frequencies. The low-frequency waves increased PM(2.5)concentrations by lowering the height over Eurasia and raising the height over the North Atlantic. The first two singular value decomposition principal patterns at the low-frequency were alike Wavenumber 3 and 4 circulations, respectively. The two patterns accounted for the majority of the background variations of winter PM(2.5)in China. The intermediate-frequency waves increased PM(2.5)concentrations via an anomalous dipole pattern over East Asia with a positive polarity over Japan and a negative polarity over Mongolia. The positive polarity is indicative of persistent haze episodes. The high-frequency waves showed a small dipole correlation pattern with PM(2.5,)but they barely accounted for high PM(2.5)concentrations. The high-frequency waves traveled quickly. They raised or lowered PM(2.5)concentrations in a short time, preventing particulate accumulations. The anomalous heights at the low- and intermediate-frequency for the PM(2.5)concentrations >90th showed a few characteristics consistent with the circulation anomalies proposed in previous climate studies with monthly mean data. Synergic effects of the waves at different frequencies result in the observed PM(2.5)variations.

Plain Language Summary Haze is an important environmental issue in northern China as a result of anthropogenic emissions and adverse weather conditions. Weather is subject to atmospheric waves at various frequencies. Low-frequency planetary waves induce seasonal circulations, whereas high-frequency synoptic waves affect weather systems on a timescale of days. These waves are associated with different fundamental driving forces and have different areas of influence. Their synergic effects lead to the observed variations in PM2.5 concentrations. This study analyzed the correlations between the winter PM2.5 concentrations in northern China and the 850 hPa geopotential height in the northern hemisphere in 2013-2019. The correlations between the atmospheric circulation and PM2.5 depend on the wave frequency and the rank of PM2.5. Slowly traveling waves are crucial for the occurrence of high PM2.5 concentrations, whereas rapidly traveling waves correlate with low PM2.5 concentrations. The anomalous heights for each frequency are not symmetrical between high and low PM2.5 concentrations. Knowledge of the characteristic circulations at different frequencies would improve our understanding of the occurrence of haze.