Visualizing the intercity correlation of PM_2.5 time series in the Beijing-Tianjin-Hebei region using ground-based air quality monitoring data - Fig 3

<p><b>Maps of intercity correlations and time lags for PM</b>_<b>2.5</b><b>time series between 17 cities in (A) February, (B) May, (C) August, and (D) November of 2014 in the Beijing-Tianjin-Hebei area.</b> The line colors refer to the strength of the correlation of the PM_2.5 time series between the two linked cities. The color bar on the right provides a scale of the correlation coefficients. The numbers on the lines refer to the time lags. Solid lines mean the correlation with the time lag is significantly larger than the correlation without the time lag at the 10% level, while the dashed lines mean the correlation with the time lag is not significantly larger than the correlation without the time lag at the 10% level. The arrows on the lines indicate the temporal order of the correlated PM_2.5 time series, where the PM_2.5 time series in the city at the tail of the arrow leads the PM_2.5 time series in the city at the head of the arrow. Map views for other months are provided in the supplementary information (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192614#pone.0192614.s001" target="_blank">S1 Fig</a>). This figure was produced using Python 2.7.5 (<a href="https://www.python.org/" target="_blank">https://www.python.org</a>) and Matplotlib 1.5.0 (<a href="https://matplotlib.org/" target="_blank">https://matplotlib.org</a>/).