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Travis O'Brien is a research scientist in the Earth Sciences Division at Lawrence Berkeley National Lab. His research focuses on developing, evaluating, and utilizing mathematical models of the Earth system to answer questions about how climate change might impact society and ecology. Travis helps lead a small community of scientists attempting to understand how changes in fog might affect coastal water resources, and he works with an interdisciplinary team at Berkeley Lab aimed at understanding the role that humans have played in changing the chances of extreme weather events.
Climate models are our one of our primary tools for investigating climatological processes and for developing detailed theories about how the climate system works. Climate modeling can be viewed as a cycle that has three main stages: model development, model characterization, and model application. As observation- and model-based studies improve our understanding of the natural world, it is often necessary to improve climate models in order to investigate new questions; model development is the stage in which we build new information into our climate models. It is important to understand the properties of these models in order to understand ways in which model phenomena may reflect natural phenomena; model characterization, which includes model validation, is the stage in which we develop a thorough understanding of the model itself and of how well the model represents nature. Climate model application is the stage in which we use a climate model to gain new understanding about how the natural climate system works. Travis is involved in all three stages of climate model-based research.
Travis is currently investigating how and why the climatology of the Community Atmosphere Model changes with model resolution (O'Brien et al.; 2013, J. Climate, and O'Brien et al. 2014, Comp. Stat. and Data Anal.). He is also developing a satellite-based climatology of coastal fog for the purposes of climate model evaluation and for climate process studies. He has published studies on the impact of intrinsic model variability on the interpretation of sensitivity studies in a regional climate model (O'Brien et al.; 2010, Clim. Dyn.) and on the validation of a regional climate model with an updated boundary layer parameterization (O'Brien et al.; 2012, Geophys. Mod. Dev.).
The bulk of Travis' dissertation work involved coupling a new turbulence (boundary layer) parameterization into a regional climate model; he coupled the University of Washington turbulence parameterization into the International Centre for Theoretical Physics's regional climate model, RegCM4.1. The new turbulence parameterization improves the representation of the physical processes that occur at the tops of stratiform clouds, and it allows RegCM4.1 to develop stratocumulus clouds and coastal fog. This effort is described in O'Brien et al. (2012, Geophys. Mod. Dev.), Giorgi et al. (2012; Clim. Res.), and O'Brien et al. (2012, Clim. Dyn.).
Travis currently serves as a volunteer developer on the RegCM development team, and he helps to maintain and develop the University of Washington code in RegCM.
Travis is using RegCM, Community Earth System Model, and various observational datasets to understand how and why California coastal fog has declined over the past century and how fog may change in the future (O'Brien 2011, PhD dissertation). So far this research has provided strong evidence that local sea surface temperatures are one of the strongest drivers of year-to-year variability in fog, and that systematic changes in near-coastal circulation (particularly a strengthening of subsidence related to a strengthening of the coastal jet) have driven the decline in fog. Current efforts involve using a coupled ocean-atmosphere modeling system to understand how changes in near-coastal upwelling may additionally change coastal fog.