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Impact of the 2015 El Nino event on winter air quality in China

View Article: PubMed Central - PubMed

ABSTRACT

During the winter of 2015, there was a strong El Nino (ENSO) event, resulting in significant anomalies for meteorological conditions in China. Analysis shows that the meteorological conditions in December 2015 (compared to December 2014) had several important anomalies, including the following: (1) the surface southeasterly winds were significantly enhanced in the North China Plain (NCP); (2) the precipitation was increased in the south of eastern China; and (3) the wind speeds were decreased in the middle-north of eastern China, while slightly increased in the south of eastern China. These meteorological anomalies produced important impacts on the aerosol pollution in eastern China. In the NCP region, the PM2.5 concentrations were significantly increased, with a maximum increase of 80–100 μg m−3. A global chemical/transport model (MOZART-4) was applied to study the individual contribution of the changes in winds and precipitation to PM2.5 concentrations. This study suggests that the 2015El Nino event had significant effects on air pollution in eastern China, especially in the NCP region, including the capital city of Beijing, in which aerosol pollution was significantly enhanced in the already heavily polluted capital city of China.

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(a) Anomalies of monthly mean general circulation between Dec. 2015 and Dec. 2014 in eastern Asia. The shaded and the white lines represent the sea level pressure (hPa) and the vectors for the 10-meter wind field (m s−1). NCEP/NCAR re-analysis data were applied in the study. (b) Same as (a), except at 500 hPa. The Data/image provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd. The map was generated by The NCAR Command Language (Version 6.3.0) [Software]. (2016). Boulder, Colorado: UCAR/NCAR/CISL/TDD. http://dx.doi.org/10.5065/D6WD3XH5.
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f1: (a) Anomalies of monthly mean general circulation between Dec. 2015 and Dec. 2014 in eastern Asia. The shaded and the white lines represent the sea level pressure (hPa) and the vectors for the 10-meter wind field (m s−1). NCEP/NCAR re-analysis data were applied in the study. (b) Same as (a), except at 500 hPa. The Data/image provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd. The map was generated by The NCAR Command Language (Version 6.3.0) [Software]. (2016). Boulder, Colorado: UCAR/NCAR/CISL/TDD. http://dx.doi.org/10.5065/D6WD3XH5.

Mentions: To understand the impact of the 2015-ENSO on the air pollution in China, we first study the anomalies of weather conditions by comparing the large-scale circulations between Dec. 2015 and Dec. 2014 (i.e., the monthly mean values in 2015 minus the monthly mean values in 2014). Figure 1a shows the anomalies of sea level pressure (hPa) and 10-meter wind speed (m s−1). The results show that there were significant positive anomalies of sea level pressure (SLP) in the Aleutian region but negative anomalies of SLP in the Asian continent. For example, the SLP in the Aleutian region was about 4–10 hPa higher in December 2015 than in December 2014. In contrast, the SLP in the Asian continent was about 4–10 hPa lower in December 2015 than in December 2014. As a result, the anomalies of the SLP in the two regions enhanced southeasterly winds nearby the surface in eastern China, especially in the NCP region. As shown in Fig. 1a, the southeasterly winds in the NCP region (32°–40°N, 114°–121°E) during 2015-ENSO were enhanced by 4–5 m s−1. Several previous studies suggested that the occurrences of heavy haze events in the NCP (characterized by daily mean concentrations of PM2.5 being greater than 100 μg m−3) were significantly dependent on the wind directions26. As a result, the enhanced southeasterly winds played important roles in increasing the haze occurrences in the NCP (see Fig. S1 of the supplementary information for detailed explanations).


Impact of the 2015 El Nino event on winter air quality in China
(a) Anomalies of monthly mean general circulation between Dec. 2015 and Dec. 2014 in eastern Asia. The shaded and the white lines represent the sea level pressure (hPa) and the vectors for the 10-meter wind field (m s−1). NCEP/NCAR re-analysis data were applied in the study. (b) Same as (a), except at 500 hPa. The Data/image provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd. The map was generated by The NCAR Command Language (Version 6.3.0) [Software]. (2016). Boulder, Colorado: UCAR/NCAR/CISL/TDD. http://dx.doi.org/10.5065/D6WD3XH5.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037463&req=5

f1: (a) Anomalies of monthly mean general circulation between Dec. 2015 and Dec. 2014 in eastern Asia. The shaded and the white lines represent the sea level pressure (hPa) and the vectors for the 10-meter wind field (m s−1). NCEP/NCAR re-analysis data were applied in the study. (b) Same as (a), except at 500 hPa. The Data/image provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd. The map was generated by The NCAR Command Language (Version 6.3.0) [Software]. (2016). Boulder, Colorado: UCAR/NCAR/CISL/TDD. http://dx.doi.org/10.5065/D6WD3XH5.
Mentions: To understand the impact of the 2015-ENSO on the air pollution in China, we first study the anomalies of weather conditions by comparing the large-scale circulations between Dec. 2015 and Dec. 2014 (i.e., the monthly mean values in 2015 minus the monthly mean values in 2014). Figure 1a shows the anomalies of sea level pressure (hPa) and 10-meter wind speed (m s−1). The results show that there were significant positive anomalies of sea level pressure (SLP) in the Aleutian region but negative anomalies of SLP in the Asian continent. For example, the SLP in the Aleutian region was about 4–10 hPa higher in December 2015 than in December 2014. In contrast, the SLP in the Asian continent was about 4–10 hPa lower in December 2015 than in December 2014. As a result, the anomalies of the SLP in the two regions enhanced southeasterly winds nearby the surface in eastern China, especially in the NCP region. As shown in Fig. 1a, the southeasterly winds in the NCP region (32°–40°N, 114°–121°E) during 2015-ENSO were enhanced by 4–5 m s−1. Several previous studies suggested that the occurrences of heavy haze events in the NCP (characterized by daily mean concentrations of PM2.5 being greater than 100 μg m−3) were significantly dependent on the wind directions26. As a result, the enhanced southeasterly winds played important roles in increasing the haze occurrences in the NCP (see Fig. S1 of the supplementary information for detailed explanations).

View Article: PubMed Central - PubMed

ABSTRACT

During the winter of 2015, there was a strong El Nino (ENSO) event, resulting in significant anomalies for meteorological conditions in China. Analysis shows that the meteorological conditions in December 2015 (compared to December 2014) had several important anomalies, including the following: (1) the surface southeasterly winds were significantly enhanced in the North China Plain (NCP); (2) the precipitation was increased in the south of eastern China; and (3) the wind speeds were decreased in the middle-north of eastern China, while slightly increased in the south of eastern China. These meteorological anomalies produced important impacts on the aerosol pollution in eastern China. In the NCP region, the PM2.5 concentrations were significantly increased, with a maximum increase of 80–100 μg m−3. A global chemical/transport model (MOZART-4) was applied to study the individual contribution of the changes in winds and precipitation to PM2.5 concentrations. This study suggests that the 2015El Nino event had significant effects on air pollution in eastern China, especially in the NCP region, including the capital city of Beijing, in which aerosol pollution was significantly enhanced in the already heavily polluted capital city of China.

No MeSH data available.


Related in: MedlinePlus