Variability and change in mountain climates

About half the fresh water used by humans originates in mountains. In regions like the Pacific Northwest, winter snowpack provides vital water resources during the dry summer melt season. I’m interested in the mechanisms controlling the amount and distribution of mountain precipitation and snowpack, and their implications for how mountain climates might change in a warmer world.

Energetic constraints on the global hydrologic cycle

The hydrologic cycle plays an important role in the atmospheric heat engine. Most water vapor in the atmosphere evaporates from tropical oceans, where much of the sun’s energy is absorbed, while most condensation occurs at higher altitudes and/or latitudes, where temperatures are cooler. This movement of heat from warm to cool regions drives the atmospheric motions that characterize our weather and climate. I use simple models to try to better understand this energy transport, its relationship to atmospheric dynamics, and its response to climate change.

Cloud feedback and climate sensitivity

Much of the disagreement in model projections of future warming comes from uncertainty in how warmer temperatures will affect clouds. I’m interested in why the cloud feedback and climate sensitivity differ among models, and in using observations to evaluate which models are the most believable.

Regional climate variability and predictability

Much of the seasonal-to-decadal scale climate variability in the Western US is driven by sea-surface temperature (SST) fluctuations in the tropical oceans. The most important of these is El Nino, which tends to bring wet conditions to California and dry conditions to the Pacific Northwest. This response is not guaranteed, however, in part because of chaos in the atmosphere, but also because of other patterns of tropical SST variability that are not well understood. I want to better understand these patterns, their impacts, and their representation in forecast and climate models.