Description: The probability of detection (with values shown along the y-axis on the left) is a measure of event occurrence detected by the forecast. False Alarm Rate (FAR) is a measure of event occurrence incorrectly predicted by the forecast. Success ratio (with values shown along the x-axis) is 1-FAR. Critical Success Index (CSI; shaded area with values shown along the y-axis on the right) is also a measure of successful event forecasts, but with consideration of both sample size of forecasts and of observed events. Frequency bias (dashed lines) is a measure of over- and under-estimates made by the forecast. The closer that a point is to a value of 1.0 of all performance metrics in the diagram (i.e., the upper-right corner), the more accurate the forecasts on daily mean concentration of particulate matter of fine particles with diameters ≤2.5 micrometers (PM2.5) were over the contiguous U.S. (CONUS) during the last 31 days. The black line represents the raw AQM forecast and the red line represents the bias-corrected AQM forecast.