In this graph, we present hourly mean PM2.5 from December 2015 through January 2016 in order to examine variation in pollution over the course of the day. PM2.5 remains consistently high from 10:00PM to 10:00AM, at which point it starts decreasing to reach the daily low at 4:00PM and 5:00PM. From 5:00PM to 10:00PM, it steadily increases again. The nightly mean from 10:00PM to 10:00AM is 302μg/m3, and the daily mean is 224μg/m3. Between 4:00PM and 5:00PM, mean PM2.5 is 169μg/m3. The hourly 25thpercentiles over these two months are never below the limit set by the Indian government.
Means present hourly averages of hourly observations. Similarly, hourly minimums and maximums are displayed using bars, and 25th and 75thpercentiles are displayed using horizontal markers. Data are from the US Embassy, Chanakyapuri, New Delhi.
This graph has been published in Plos One, “An experiment with air purifiers in Delhi during winter 2015-2016.”