We work on a range of topics related to precipitation extremes and dynamics of the climate system. Current research is largely focused on the characterization of atmospheric rivers, but future directions include precipitation extremes more generally. Below is a brief description of active projects:
Atmospheric River Tracking Method Intercomparison Project (ARTMIP)
Atmospheric rivers (ARs) are long, filamentary structures that transport large quantities of moisture northward, typically from the tropics and subtropics into the mid-latitudes. The goal of ARTMIP is to understand and quantify the uncertainties in AR science due to the tracking or identification methodology alone. Many AR detection techniques are currently employed for a number of purposes, and the literature reports a wide range of conclusions based on these techniques. ARTMIP strives to provide the community with information and guidance on different methodologies for a given science question or region of interest.
ARTMIP is a multi-tier project. In the first tier, participants ran their algorithms on a common dataset (MERRA-2) in order to establish baseline comparisons in feature detection. Ashley will lead the first project of the second tier. The aim of this project is to comprehensively investigate the response of ARs to climate change. Participants will run their algorithms over high resolution climate change model output from the International CLIVAR C20C+ Detection and Attribution Project.
Representation of precipitation extremes in variable resolution GCMs
Progress on the representation of precipitation in climate models is of essential importance in agriculturally significant areas, such as the Great Plains, where climate change may perturb human adaption to an already harsh environment. Models with high enough resolution to explicitly resolve convection show improved representation of precipitation and mesoscale convective systems. The fine spatial resolutions needed for these approaches can be computationally costly for traditional global climate models, and subject to boundary conditions in regional climate models. Newly developed variable-resolution global climate models keep the benefits of high-resolution regional climate models and the large-scale dynamics of global climate models, while also keeping computational costs down. However, with new variable-resolution models, the problems inherent to traditional convective parameterization approaches remain. In order to further improve model simulations and advance their use, variable resolution models must be assessed in order to better understand sources of uncertainty. Current work includes an evaluation of the development and behavior of three mesoscale convective systems using short three day hindcasts.
Dynamical controls on atmospheric river behavior
Landfalling ARs are linked to severe flooding and precipitation events, most notably along the western coastlines of continents. ARs are primarily episodic features and exhibit large variability in their location of landfall, intensity and duration along the coastline. Among other factors, spatially and temporally persistent AR events are highly correlated to large hydrological impacts at landfall. Advanced warning of these hydrologically significant landfalling events can be improved through a better understanding of the mechanisms leading to their formation and evolution prior to landfall. The focus of this research is on the interaction and feedback between intense lower-level moisture transport and associated upper-level dynamics as well as common weather regimes associated with persistent events. Recent work on this topic has centered along the western coastline of North America and Scandinavia.