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Volume 15, issue 20 | Copyright

Special issue: Haze-fog forecasts and near real time (NRT) data application...

Atmos. Chem. Phys., 15, 11919-11929, 2015
https://doi.org/10.5194/acp-15-11919-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 27 Oct 2015

Research article | 27 Oct 2015

A new indicator on the impact of large-scale circulation on wintertime particulate matter pollution over China

B. Jia1,2, Y. Wang1,2,3, Y. Yao1, and Y. Xie1 B. Jia et al.
  • 1Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, Tsinghua University, Beijing, China
  • 2Department of Marine Sciences, Texas A&M University at Galveston, Galveston, TX, USA
  • 3Department of Atmospheric Sciences, Texas A&M University, College Station, TX, USA

Abstract. Extreme particulate matter (PM) air pollution of January 2013 in China was found to be associated with an anomalous eastward extension of the Siberian High (SH). We developed a Siberian High position index (SHPI), which depicts the mean longitudinal position of the SH, as a new indicator of the large-scale circulation pattern that controls wintertime air quality in China. This SHPI explains 58 % (correlation coefficient of 0.76) of the interannual variability of wintertime aerosol optical depth (AOD) retrieved by MODIS over North China (NC) during 2001–2013. By contrast, the intensity-based conventional Siberian High index (SHI) shows essentially no skill in predicting this AOD variability. On the monthly scale, some high-AOD months for NC are accompanied with extremely high SHPIs; notably, extreme PM pollution of January 2013 can be explained by the SHPI value exceeding 2.6 times the standard deviation of the 2001–2013 January mean. When the SH extends eastward, thus higher SHPI, prevailing northwesterly winds over NC are suppressed not only in the lower troposphere but also in the middle troposphere, leading to reduced southward transport of pollution from NC to South China (SC). The SHPI hence exhibits a significantly negative correlation of −0.82 with MODIS AOD over SC during 2001–2013, although the robustness of this correlation depends on that of satellite-derived AOD. The suppressed northwesterly winds during high-SHPI winters also lead to increased relative humidity (RH) over NC. Both the wind and RH changes are responsible for enhanced PM pollution over NC during the high-SHPI winters.

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We developed a new indicator, Siberian High position index (SHPI), which depicts the mean longitudinal position of the SH, as a new indicator of the large-scale circulation pattern that controls wintertime air quality in China. This SHPI explains 58% and 64% of the interannual variability of winter AOD during 2001-2013 over North China and South China, respectively. The extreme PM pollution of January 2013 is found to be associated with extremely high values of SHPI.
We developed a new indicator, Siberian High position index (SHPI), which depicts the mean...
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