Winter Stormchasing in the Northeastern US

The Investigation of Microphysics and Precipitation in Atlantic Coast-Threatening Snowstorms (IMPACTS) is a five-year Earth Venture Suborbital (EVS-3) NASA aircraft-based field campaign to collect simultaneous remote sensing and mid-cloud observations of Northeastern U.S. winter storms. Using 3 active radars, 2 passive radars, lidar, microphysics probes, turbulence sensors, dropsondes, as well as a host of ground crews, we are able to get a comprehensive view of snowstorms for the first time in over 30 years.

NE US snowstorms commonly exhibit linear banded patterns of heavier precipition within areas of lighter precipitation in the storm. We call these structures ‘snowbands’, and one of the major goals of this field campaign is to better understand the processes that control how the snowbands are initiated and evolve over the lifetime of the storm. Our work will ultimately result in better, more accurate forecasts of both the location and timing of heavy snowfall, which will help emergency response and community planning in one of the most densely populated regions of North America.

For my MS thesis, I mainly used the radar observations collected from the high-altitude ER-2 aircraft to study how dynamical processes such as convergence, deformation in the temperature gradient (frontogenesis), and/or waves in the atmosphere contribute to the vertical motion that controls the organization and evolution of snowbands.

IMPACTS Press

NASA snowstorm study will send planes inside of East Coast storms - Mic.com (2020)
NASA ‘snow hunters’ to fly into East Coast storms to improve forecasts - Washington Post (2020)
NASA Taps Snowstorm-Chasing Team To Improve Forecasting - NPR (2020)
UW scientist to lead NASA field study of East Coast snowstorms - UW News (2019)

Climate Modelling to Study Ancient Clouds

At the University of Victoria I ran a series of global climate model experiments to study what role cloud feedbacks have in stabilizing climate over geologic timescales. During the Archean (~2.5 - 4 billion years ago), the Sun was ~20% dimmer than it is today, but Earth wasn’t colder. To compensate for less sunlight, we added more carbon dioxide to the model atmosphere to give a stronger greenhouse effect, creating a series of climates with the same annual global mean surface temperature as present day Earth. We found that in climates with less sunlight but more CO2, the boundary layer inversion weakens, allowing the low stratocumulus clouds that are normally trapped there to dry out and warm up, significantly reducing low cloud cover compared to present day. Fewer low clouds allows a higher fraction of the available sunlight to reach the surface, which contributes ~40% of the heating required to counteract the decreased sunlight and avoid widespread glaciation. Because of this physical cloud feedback, we were able to keep the global mean surface temperature the same as present day with 3x less CO2 than expected from 1D models that assume only geochemical feedback processes. This is a new physical mechanism that helps resolve the Faint Young Sun problem, allowing the geochemical feedbacks that have been relied on in previous studies to play a smaller role, and stay within the ranges allowed by proxies.