Global PM2.5 Long Term Time Series - NASA's MERRA 2 Reanalysis 
Time series (1980-2017) visualization of monthly mean PM2.5 mass concentration (micro gm-3) over 2000+ cities/monitoring locations worldwide.  The visualization provides qualitative changes for past four decades using reanalysis data in absence of real measurements from ground monitoring stations. The tool allows users to compare trends over three cities. Please see the tutorials for details. Validation and improvements are in the progress and if you like to contribute, we welcome your participation and also your feedback.

Brief description: Various aerosol components from NASA’s MERRA-2 reanalysis data have been used to reconstruct PM2.5 mass concentration using scientific methods outlined by ( e.g., Malm et al., 1994; Chow et al., 2015; T urpin and Lim, 2001; Provencal et al., 2017). MERRA-2 is the first long-term global reanalysis of atmospheric aerosol components and are at a spatial resolution of 0.5 latitude × 0.625 longitude. NASA’s GEOS system assimilates aerosol products ( Randles et al., 2017) from multiple satellites and surface measurements to produce the MERRA-2. Noticeable changes may appear in PM2.5 trends (specifically before the year 2000) and one should be cautious in using MERRA-2 aerosol data for quantifying aerosols trends over the entire period. High-quality satellite observations of aerosols are only available after 2000 (EOS Terra and Aqua). For more details, please refer to documents and publications.