Spatial and Temporal Variabilty in PM2.5 in NAPA Valley, CA August-October 2020
WILLIAM MILLS, Justin Cathey,
Northern Illinois University Abstract Number: 766
Working Group: Aerosols Spanning Spatial Scales: Measurement Networks to Models and Satellites
AbstractThe LNU Lightning Complex (August 17-October 2, 2020) and Glass (September 27-October 20, 2020) Fires burned during the 2020 California wildfire season. A total of 23 PurpleAir stations were identified in Napa Valley with PM
2.5 monitoring data for at least part of the August 1-October 31, 2020 time period. PM
2.5 data (10 minute and daily average, uncorrected and corrected using a US EPA correction factor) from these stations were analysed to provide information on spatial and temporal variability of the PM
2.5 during this time period and to assess the impact from these fires on local air quality. Noticeable elevations (attributed to the LNU Lightning Complex Fire) were seen for some stations, in mid-August, end of August and mid-September, however peak levels during these time periods were significantly less than those observed at most stations during the Glass fire. Correlation analyses showed excellent agreement (high R^2 and slope=1) between adjacent monitoring locations during the Glass Fire. These same analyses showed well-correlated but lower concentrations further from the fire for the initial 3-4 hrs (0300-0700 hrs) after which the Napa Valley sites all plateaued at approximately the same high PM
2.5 levels (100-300 ug/m^4) but dropped in mid-day until early evening time period and then became elevated again at many locations. These trends are consistent with the eye witness descriptions and aerial imagery of the Glass Fire footprint and behaviour over the first day. Estimates of PM
2.5 concentrations on a property near the source were made based on regression analysis of PM
2.5 versus distance from the nearest station. Heatmap data visualization was used to show the PM
2.5 concentrations in Napa Valley for several time points. This analysis work illustrates the utility of the PurpleAir monitoring network for observing impacts from wildfires on local air quality.