This graph depicts daily variation in PM2.5 over December 2015 through January 2016. Over this period of time, neither the daily mean PM2.5 nor the 25th percentile ever fell as low as the Indian government limit of 60μg/m3. The lowest daily mean was 149μg/m3, the highest daily mean was 460μg/m3, and the mean daily mean was 260μg/m3 over these two months. This panel also suggests a correlation in the daily mean over time. In fact, 79% of the variation in the daily mean can be statistically explained by its first lag in a regression of daily mean PM2.5 on the previous day’s mean PM2.5.
Means present daily averages of hourly observations. Similarly, daily minimums and maximums are displayed using bars, and 25th and 75th percentiles 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.”