Characterization of intra-continental smoke transport and impact on New York State air quality using aerosol reanalysis and multi-platform observations

Abstract

Smoke aerosols emitted by wildfires can ascend to the free troposphere, travel over long distances and descend to affect local air quality (AQ) in downwind areas. This study investigates the AQ impact of long-range transported (LRT) smoke aerosols from western North America during summer 2017 in New York State (NYS) using observations and numerical products. Analysis of total fine particulate matter (PM2.5) and black carbon measurements at Queens and Buffalo shows that about 38% and 43% of the polluted events are related to the LRT smoke aerosols, respectively. Two LRT smoke events transported from the Pacific Northwest to NYS on Sep. 5 and 16, 2017, are analyzed. The transport path is determined by the large-scale flow (positive tilted trough for the 1st case and stationary front for the 2nd case). During both events, smoke aerosols were entrained into the boundary layer during the growth of the planetary boundary layer (PBL) and accumulated near surface when the PBL collapsed. The enhanced aerosol mass is primarily due to carbonaceous and secondary sulfate aerosols. Although the two events differed in aerosol loadings (150 versus 80 mg m−2 for column mass density), weather conditions (cold front passage versus high-pressure system), and entrainment rates (6 versus 12 cm s−1), the AQ impacts were comparable for two events (about 10 μg m−3 increase of total PM2.5). Our study of two smoke cases indicates that the LRT smoke events even with moderate intensity would degrade local AQ if the underlying meteorological conditions are favorable for downward mixing.