Scientist and numerical modeler bringing clarity to complex problems in the Earth system.
The stratospheric circulation leading up to the 2021 cold air outbreak in observations and experimental forecasts.
Pathways of planetary-scale atmospheric waves across the Pacific indicate that less than 3% of the wave forcing for the event reflected off the polar vortex.
In forecasts, surface temperatures over North America are frigid - even when the stratosphere is artificially engineered to shut down the wave reflection mechanism.
Did stratospheric dynamics drive the deadly February 2021 cold air outbreak in the United States? Unconventional but simple modifications to the initial conditions of numerical forecasts provide a decisive answer: no.
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Forecasts that are unsuccessful and successful at predicting a sudden stratospheric warming, and the verification (MERRA2). Here, "unsuccessful" means a false negative - a forecast should have predicted a sudden warming, but didn't. All composites relative to the sudden warming date.
Regression of wave drag, residual mean angular momentum flux convergence, and net momentum tendency on stratospheric jet deceleration during a sudden stratospheric warming.
Composites of jet-level momentum budget terms with the (black) correct zonal mean and (red) the zonal mean from the other composite.
How can you improve the prediction of sudden stratospheric warmings? By investigating the physical process that is equal and opposite to the wave drag driving the event.
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Refining the global grid over North America can resolve gravity wave dynamics, including horizontal propagation that isn't captured by parameterizations.
Spectrally decomposing the circulation in space and time provides deep insights into vertical transport.
A gravity wave produced by flow over the Rocky Mountains reaches well into the stratosphere, and is associated with a localized injection of stratospheric ozone toward the surface.
Gravity waves transport momentum and constituents between space, Earth’s surface, and everywhere in between. They can only be resolved in high-resolution simulations. How can we leverage hundreds of terabytes of model output from short, expensive model simulations to generate a deeper understanding of their impact on the climate system?
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The zonal wind responses, as for temperature. Equal and opposite responses highlight which processes drive - and which diffuse - the global response.
The Hadley and Ferrel cell responses, as for temperature. By restricting the circulation responses, we can build a more direct and predictive understanding of global change.
Modeling all of these complicated changes in the atmospheric circulation with a simple mathematical hypothesis. A special model experiment confirms the hypothesis (red).
Idealized modeling experiments are ubiquitous - but the forcing they impose is fundamentally at odds with the real effects of greenhouse gases.
The temperature response to a CO2-like forcing in an idealized model with varying degrees of the circulation held to its control state. The minor differences between these experiments is key to unlocking the global response to forcings.
Tropical upper-tropospheric heating is often applied to idealized models as an analogue to CO2 forcing, but this is opposite to the actual CO2 forcing. This study uses a model with simplified but interactive radiation to avoid the pitfalls of choosing your own forcing.