Abstract
Extremely high fine particulate matter (PM2.5) concentration has become synonymous to Beijing, the capital of China, posing critical challenges to its sustainable development and leading to major public health concerns. In order to formulate mitigation measures and policies, knowledge on PM2.5 variation patterns should be obtained. While previous studies are limited either because of availability of data, or because of problematic a priori assumptions that PM2.5 concentration follows subjective seasonal, monthly, or weekly patterns, our study aims to reveal the data on a daily basis through visualization rather than imposing subjective periodic patterns upon the data. To achieve this, we conduct two time-series cluster analyses on full-year PM2.5 data in Beijing in 2014, and provide an innovative calendar visualization of PM2.5 measurements throughout the year. Insights from the analysis on temporal variation of PM2.5 concentration show that there are three diurnal patterns and no weekly patterns; seasonal patterns exist but they do not follow a strict temporal division. These findings advance current understanding on temporal patterns in PM2.5 data and offer a different perspective which can help with policy formulation on PM2.5 mitigation.
Highlights
Beijing, the capital of China where more than 20 million people reside, would probably never have considered it would gain the title “Capital of Smog” that was used for London 60 years ago
We obtain three clusters for the analysis based on correlation distance, and each of them has 162, 117, and 86 time-series
The third pattern with a shape like an inverted V often take place from April to August (S3 in Fig. 1a,c) and the PM2.5 concentrations during these days usually peaks at noon. These results show that the diurnal patterns of PM2.5 vary from day to day through the year, and PM2.5 concentration in the daytime could be higher than at night in many days, which complement previous studies concluding that diurnal variation of PM2.5 change by seasons and PM2.5 concentration at night is higher than that in the daytime[10,16]
Summary
Particulate Matter Time Series in Beijing: A Calendar View received: 26 January 2016 accepted: 04 August 2016 Published: 26 August 2016. There have been studies that analysed PM2.5 measurements data in a full year across Beijing that were provided by the newly launched air pollution monitoring network since later 20129,10,15,16, but these studies, when analysing the temporal variation of PM2.5 concentration, used an a priori assumption that PM2.5 concentration follows seasonal, monthly, or weekly patterns. Our study presents an innovative and straightforward calendar visualization of daily PM2.5 time-series in Beijing in the year of 2014 This technique provides a very useful tool to visualize and understand the data and can be applied to examine temporal patterns of other air pollutants. Compared to previous studies on Beijing’s PM2.5 concentration, our study offers a different perspective and brings in insights on PM2.5 concentration that are more complete and convincing
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