WE-CAN

Overview

Understanding the chemistry in western wildfire smoke has major ramifications for air quality, nutrient cycles, weather and climate. The Western wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) project systematically characterizes the emissions and first day of evolution of western U.S. wildfire plumes, focusing on three sets of scientific questions related to fixed nitrogen, absorbing aerosols, and cloud activation and chemistry in wildfire plumes. The data were collected from the NCAR/NSF C-130 research aircraft.

Intellectual Merit

The first day of processing is a major driver of the eventual air quality and climate significance of wildfire smoke because the chemistry and micro-physics occurring during this time impacts the partitioning of reactive nitrogen, alters cloud chemistry and nucleation, and determines aerosol scattering and absorption. The evolution and partitioning of fixed nitrogen is central to within-plume free radicals and oxidant production, thus secondary pollutant formation and removal. It also impacts the absorption of light in the plume, and the timescale and eventual form of nitrogen deposited to the surface. Brown carbon from biomass burning has a virtually unknown lifecycle, but is hypothesized to contribute significantly to the observed brown carbon that is found to be radiatively important and ubiquitous throughout the troposphere over North America in summer. The influences of wildfire smoke on amending atmospheric populations of ice nucleating particles is poorly understood, but wildfires may be distinct emitters compared to prescribed fires. Clouds are important processors of gas and particle phase species in the atmosphere, contributing both to formation of new particle mass and to particle scavenging and removal. Observations of the interactions between smoke and clouds are very limited, but they indicate strong interactions contributing substantially to the formation of secondary species. The WE-CAN project included a set of flight plans and a payload that will allow many specific questions associated with each of these processes to be answered.