ushankar@unc ie.unc/cempd

1. Assessing the Impacts on Smoke, Fire and Air Quality Due to Changes in Climate, Fuel Loads, and Wildfire Activity over the Southeastern U.S.U. Shankar1, D. McKenzie2, J. Bowden1 and L. Ran1 Background An issue of great concern on federal lands is wildfires, which have increased in frequency and intensity over the past few decades, possibly due to climate change. Modeling wildfires under an evolving climate is challenging: several spatial and temporal scale mismatches occur in characterizing wildfire emissions and their effects on ambient air quality and visibility downwind, and in forecasting changes in vegetation and fuel loads in response to the changing climate and the consequent changes in fire regimes. Many models altogether ignore these changes in future climate regimes, resulting in large uncertainties in predicting future climate impacts on fires, air quality and compliance with the National Ambient Air Quality Standards (NAAQS). This collaborative project between the University of North Carolina—Institute for the Environment and the US Forest Service seeks to address some of the issues in a modeling and analysis study over the Southeastern U.S., where managing fire and air quality is already challenging. Our approach leverages integrated modeling concepts from a white paper* submitted to the Joint Fire Sciences Program (JFSP) by McKenzie and co-authors in 2012. It includes dynamic representation of the vegetation and associated changes in fuels, changes in the spatial distribution of daily areas burned during the fire season, and the resulting impacts on smoke emissions and air quality under contemporary conditions and future climate scenarios in estimated high and low fire years. This work is supported by JFSP Award 13-1-01-16, and will begin on November 1, 2013. Weather Research and Forecasting (WRF) Model Domains Values and Benefits • A robust climate downscaling approach to capture multi-decadal changes at spatial-temporal scales appropriate for modeling fire weather in the Southeastern U.S. • An ensemble modeling approach at the regional scale to bracket the range of possible future fire regimes • Methods to estimate the spatial distribution of fires during the fire season, and to project changes in fuel loads in possible future climates over this region • Tools and methods to examine the air-quality impacts of wildfire emissions, especially on short-lived climate forcing atmospheric constituents such as carbonaceous aerosols and ozone • Public sharing of the project data and findings through the Forest Service Research Data Archive (FSRDA)†, and regional fire science consortia within the JFSP Knowledge Exchange Consortium for the South.‡ • Information to support planning at timescales from the seasonal to the decadal, to address pressing needs for anticipating and managing the evolving intensity and seasonality of wildfires Conceptual Modeling System Project Goal and Objectives • Goal: To understand the smoke consequences of future fire regimes for air quality and exceedances of the ambient air quality standards in the Southeastern U.S. • Hypotheses: (1) There are significant changes in fire regimes due to changes in fuel, which can be correlated to changes in future meteorology. (2) Representing the spatial and temporal variability of wildfires results in signifi­cantly different impacts on future-year air quality than assuming a constant spatial-temporal distribu­tion, (3) These differences can be quantified and used to support air and land management. • Objectives • Examine methods for downscaling climate variables for predicting fire weather reliably over the Southeast using Representative Concentration Pathways (RCPs) from the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) to capture years with the lowest and highest expected fire occurrences. • Use the downscaled meteorology to project fuel loads and fire activity in representative future years to estimate fire emissions. • Examine the air quality impacts of these emissions relative to the National Ambient Air Quality Standards (NAAQS) over the Southeastern U.S., using a multiscale chemistry-transport modeling of pollutants emitted in wildland fire. Modeling System Components • Regional climate: Downscaled with WRF from two General Circulation Models (GCMs), the GISSE and CESM, using the Haines Index to select high and low fire years • Dynamic vegetation: Community Land Model (CLM), possibly integrated with WRF • Fuel Mapping: Time-varying; to be developed in this work for mapping CLM’s Plant Function Types to 24 USGS vegetation types and then to fuel types in the Fuel Characteristic Classification System (FCCS) • Fire activity: Fire Scenario Builder (McKenzie et al., 2006) adapted for the Southeast; constrained by acres burned/yr estimated by USFS Southern Research Station based on Mercer and Prestemon (2005) • Smoke emissions: BlueSky (USFS); dynamic plume rise calculation in CMAQ • Chemistry-transport: CMAQ v5.0.1 with Carbon Bond 2005 (gas phase) and AERO6 (aerosol) chemistry • Will evaluate performance of Volatility Basis Set for organic aerosols generated in wildfires • Feedbacks to meteorology may be examined in sensitivity studies for selected periods with coupled WRF-CMAQ • Ten major urban areas in the Southeast will be examined in contemporary and future wildfire periods for NAAQS exceedances RCP – Representative Concentration Pathway LSF – Land-surface feedback GHG – Greenhouse gas Not included in actual model realization Ensemble of WRF Simulations Websites * www.firescience.gov †www.fs.usda.gov/rds/archive ‡ southernfireexchange.org ushankar@unc.edu http://www.ie.unc.edu/cempd 1 University of North Carolina at Chapel Hill — Institute for the Environment 2 Pacific Wildland Fire Sciences Laboratory, U.S. Forest Service