Disentangling complex interactions and feedbacks among droughts, fires, and snowpack in the western U.S. by integrating observations and models

United States (U.S.) droughts have significant impacts on climate and human systems, causing
substantial damages to the environment and socio-economic development. Droughts can trigger
chains of complex interactions among climate elements, which in turn can further affect drought
evolution. Snowpack and fires, two key elements affecting hydroclimatic and socio-economic
systems, can interact with and feed back to droughts in complicated ways, particularly in the
western U.S. For example, observations (e.g., Abatzoglou and Kolden, 2013) showed strong
correlations between burned area and drought index, snow water equivalent, and soil moisture over
Rocky Mountains in the past decades. Moreover, the western U.S. droughts are shown to increase
in the past and expected to become more frequent/intense in the future, along with increasing fires
and declining snowpack. However, our current understanding of the interactions and feedbacks
among droughts, fires, and snowpack is still very limited, which hinders accurate predictions and
projections of the U.S. droughts and related hydroclimatic and socio-economic effects. Thus, it is
imperative to have an integrated understanding and quantification of these complex interactions.
The overarching project goal is to disentangle and quantify the complex interactions and feedbacks
among droughts, fires, and snowpack in the western U.S. by integrating observations and models
to improve predictions and projections of drought characteristics and impacts. We propose to
address three key scientific questions and tasks:
1. What are the quantitative characteristics and relationships of droughts, fires, and snowpack
evolution in the western U.S. based on observations? We will integrate remote sensing and in-
situ observations to quantify the characteristics (e.g., intensity and duration) and relationships
of droughts, fires, snowpack, and environmental variables (e.g., soil moisture and precipitation)
in the western U.S., with a focus on extreme/prolonged drought events and DEWS regions.
2. How well do state-of-the-art models capture the characteristics and relationships of droughts,
fires, and snowpack evolution in the western U.S.? We will enhance and validate the Noah-MP
land surface model coupled with the Weather Research and Forecasting with Chemistry (WRF-
chem) model by implementing fire-related processes (e.g., fire occurrence, spread, heat release,
vegetation change, and aerosol emissions) that interact with droughts and snowpack.
3. What are the mechanisms for drought-fire-snowpack interactions and feedbacks in the western
U.S.? We will conduct simulations using the enhanced Noah-MP-WRF-chem model to quantify
drought-fire-snowpack interactions (e.g., through effects of fire-induced aerosol and vegetation
changes on precipitation and snow), and compare with the observational analysis in Task 1.
This project will have the following deliverables:
1. Improved understanding of interactions and feedbacks among droughts, fires, and snowpack in
the western U.S.;
2. Enhanced version of the community Noah-MP land surface model coupled with WRF-chem
that is able to capture the key interactions among droughts, fires, and snowpack processes;
3. A drought prediction model based on observations and machine learning tools for future
application and advancement in drought monitoring, warning, and prediction systems.

Climate Risk Area: Water Resources