Research
My research spans the fields of climate dynamics, wildland fire, climate modeling, drought studies, and paleoclimate to understand the oceanic and atmospheric drivers of climate extremes in a warming world.
What drives hydroclimate extremes today?
Each year, hydroclimate extremes in Western North America cause substantial loss of life, ecological damage, and economic harm. As the atmosphere warms and evaporative demand rises, drought risk will intensify and wildfire seasons will continue to break records. Using station observations, reanalysis data, and climate model simulations, I study why these events occur, specifically, the physical chain of events linking climate anomalies (such as sea-surface temperature (SST) variability in the Pacific, Rossby waves, and atmospheric humidity) to extremes such as wildfire, drought, and heat.
My work has shown that climate anomalies as early as the prior winter shape summer forest fire in California, and that the recent decline in near-surface atmospheric humidity in the interior Southwest has led to an increase in burned forest area over recent decades. I have also found that Pacific SSTs synchronously affect forest fire in the Southwestern US and Eastern Australia.
The 1970-2024 circumglobal Rossby wave trend in the upper troposphere that has suppressed precipitation over the Interior Southwestern U.S. and contributed to atmospheric drying. From Jacobson et al. (2024), J. Hydrometeorol.
How well do climate models represent the drivers of extremes?
Climate models are our primary tools for predicting and understanding how climate extremes respond to external forcings. Preparing for and predicting future extremes necessitates understanding the limitations of the models we use. I compare models with observations to find relevant systemic biases for climate extremes. My work has demonstrated that our current generation of models underestimate decadal variability in the Pacific, and tend to overestimate historical cool-season warming in the Western US (under review).
How stationary are these drivers through time?
The brevity of available observations of climate and fire limits our ability to resolve the influence of natural climate variability operating on multidecadal timescales, and may not capture important nonstationarities in the influence of certain modes of variability. My ongoing work uses tree-ring reconstructions of climate over the last millennium to test whether the relationships between ocean-atmospheric anomalies and extremes have shifted, and compares these findings with CMIP6 projections through the end of the century.