Figure 4.
Monthly average PM2.5 climatology (in μg m−3) for 1997–2014 estimated using machine learning. The overlaid color filled circles are a climatology of available observations.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.