Modeling Study of the Air Quality Impact of Record-Breaking Southern California Wildfires in December 2017.
Hongrong Shi, Zhe Jiang, Bin Zhao, Zhijin Li, Yang Chen, Yu Gu, Jonathan H Jiang, Meemong Lee, Kuo-Nan Liou, Jessica L Neu, Vivienne H Payne, Hui Su, Yuan Wang, Marcin Witek, John Worden
Author Information
Hongrong Shi: Joint Institute for Regional Earth System Science & Engineering, University of California, Los Angeles, CA, USA.
Zhe Jiang: Joint Institute for Regional Earth System Science & Engineering, University of California, Los Angeles, CA, USA.
Bin Zhao: Joint Institute for Regional Earth System Science & Engineering, University of California, Los Angeles, CA, USA. ORCID
Zhijin Li: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. ORCID
Yang Chen: Department of Earth System Science, University of California, Irvine, CA, USA. ORCID
Yu Gu: Joint Institute for Regional Earth System Science & Engineering, University of California, Los Angeles, CA, USA. ORCID
Jonathan H Jiang: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. ORCID
Meemong Lee: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Kuo-Nan Liou: Joint Institute for Regional Earth System Science & Engineering, University of California, Los Angeles, CA, USA.
Jessica L Neu: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Vivienne H Payne: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. ORCID
Hui Su: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. ORCID
Yuan Wang: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
Marcin Witek: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. ORCID
John Worden: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
We investigate the air quality impact of record-breaking wildfires in Southern California during 5-18 December 2017 using the Weather Research and Forecasting model with Chemistry in combination with satellite and surface observations. This wildfire event was driven by dry and strong offshore Santa Ana winds, which played a critical role in fire formation and air pollutant transport. By utilizing fire emissions derived from the high-resolution (375 × 375 m) Visible Infrared Imaging Radiometer Suite active fire detections, the simulated magnitude and temporal evolution of fine particulate matter (PM) concentrations agree reasonably well with surface observations (normalized mean bias = 4.0%). Meanwhile, the model could generally capture the spatial pattern of aerosol optical depth from satellite observations. Sensitivity tests reveal that using a high spatial resolution for fire emissions and a reasonable treatment of plume rise (a fair split between emissions injected at surface and those lifted to upper levels) is important for achieving decent PM simulation results. Biases in PM simulation are relatively large (about 50%) during the period with the strongest Santa Ana wind, due to a possible underestimation of burning area and uncertainty in wind field variation. The 2017 December fire event increases the 14-day averaged PM concentrations by up to 231.2 μg/m over the downwind regions, which substantially exceeds the U.S. air quality standards, potentially leading to adverse health impacts. The human exposure to fire-induced PM accounts for 14-42% of the annual total PM exposure in areas impacted by the fire plumes.
