Sample MODIS aerosol optical depth (AOD)/ In-situ PM 2.5 correlation summary plot

The MODIS (the Moderate Resolution Imaging Spectroradiometer) Aerosol Optical Depth (AOD)/ In-situ PM2.5 (Particulate Matter with a diameter smaller than 2.5 microns) correlation summary plot details the correlation between AOD and surface PM2.5 across the United States and parts of Canada. The correlation is based on coincident MODIS AOD pixels and 1-hour PM 2.5 concentrations for the in-situ continuous monitors. The parameter plotted is the monitoring site-specific running correlation coefficient during the preceding 60 days (in color scale). The correlation coefficient has values between 1 (perfectly correlated) and -1 (perfectly anti-correlated). A value of zero indicates that the two measurements vary independently of each other.

The running time period is indicated in the title of the plot, (i.e., 20040403-20040602). The size of the point plotted relates to the number of coincidences between MODIS AOD pixels and 1-hour PM 2.5 concentrations for the given period. The significance of the correlation generally increases with increasing number of coincidences.

The correlation plot provides site specific and regional perspectives on the utility of MODIS AOD observations for interpreting surface PM 2.5 concentrations. Higher correlations suggest the MODIS AOD pixel is reflective of in-situ surface PM 2.5 mass concentrations at the monitor location.