Abstract
Wildfire emissions affect downwind air quality and human health. Predictions of these impacts using models are limited by uncertainties in emissions and chemical evolution of smoke plumes. Using high-time-resolution aircraft measurements, we illustrate spatial variations that can exist within a plume due to differences in the photochemical environment. Horizontal and vertical crosswind gradients of dilution-corrected mixing ratios were observed in midday plumes for reactive compounds and their oxidation products, such as nitrous acid, catechol, and ozone, likely due to faster photochemistry in optically thinner plume edges relative to darker plume cores. Gradients in plumes emitted close to sunset are characterized by titration of O3 in the plume and reduced or no gradient formation. We show how crosswind gradients can lead to underestimated emission ratios for reactive compounds and overestimated emission ratios for oxidation products. These observations will lead to improved predictions of wildfire emissions, evolution, and impacts across daytime and nighttime.
| Original language | English |
|---|---|
| Article number | e2021GL095443 |
| Journal | Geophysical Research Letters |
| Volume | 48 |
| Issue number | 23 |
| DOIs | |
| State | Published - Dec 16 2021 |
Funding
The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE‐CAN) field campaign took place in the Western U.S. July‐September 2018. Measurements were taken using a suite of instruments installed aboard a C‐130 aircraft operated by the National Center for Atmospheric Research (NCAR) and the National Science Foundation (NSF). The C‐130 sampled nearly two dozen individual wildfire plumes, targeting fresh emissions and aging up to several hours. Measurements from the Taylor Creek Fire and the South Sugarloaf Fire plumes are presented below as examples, followed by a broader analysis of all plumes during WE‐CAN. B. B. Palm, Q. Peng, and J. A. Thornton were supported by the US National Science Foundation (NSF; AGS‐1652688) and National Oceanic and Atmospheric Administration (NOAA; NA17OAR4310012). This research was supported by the U.S. NSF (AGS‐1650786 and AGS‐1650275). We thank everyone involved in planning and operations during WE‐CAN. This material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the NSF under Cooperative Agreement 1852977. The operational and scientific support from NCAR's Earth Observing Laboratory and Research Aircraft Facility is gratefully acknowledged.
| Funders | Funder number |
|---|---|
| AGS‐1650786, AGS‐1650275 | |
| AGS‐1652688 | |
| National Oceanic and Atmospheric Administration | NA17OAR4310012 |
| National Center for Atmospheric Research | 1852977 |
Keywords
- biomass burning
- fire emissions
- hydroxyl radical
- plume chemistry
- plume evolution
- wildfire
