Coastal Climate

We view the study of coastal climate as a critical focus area for our regional climate dynamics research for two reasons. First, nearly half the world's population lives within 100km of the coast, so that coastal climate processes have a disproportionate impact on humans. Second, with complex coastlines and topography, the coastal zone is often characterized by sharp climate gradients unresolved in conventional global climate models. Thus understanding climate in these areas practically requires a regional, high-resolution approach. One of our laboratories for studying coastal climate has been Southern California. We examined the region's modes of atmospheric variability in a high-resolution (6-km) regional simulation, finding that the region has its own unique modes of variability whose timing and structure cannot be related in any simple way to larger-scale atmospheric patterns. In a follow-on study, we investigated the dynamics of one of these modes, the region's famous Santa Ana winds. We have also examined how coastal topography shapes the region's hydrologic cycle and diurnal cycles of temperature and circulation. Finally, analyzing simulations with our newly-developed regional coupled ocean-atmosphere model, we've demonstrated that mesoscale processes govern air-sea interaction in the region, shaping upwelling and and regional ocean circulation. Another of our laboratories for studying coastal climate is the region encompassing Peru, northern Chile region, and the adjacent southeast Pacific, and studies of this region are forthcoming. This is part of our participation in the VOCALS project.

Regional Climate Change 

Building on our work examining the dynamics of Southern California's Santa Ana winds in the current climate, we undertook a regional climate change modeling study of the changes in these wind patterns resulting from increasing greenhouse gases. It turns out these winds decrease in intensity in the future simulation, largely due to a weakening wintertime temperature difference between the Mojave Desert and the coast. Changes in the hydrologic cycle at the regional scale are a potentially critical dimension of climate change, but are poorly understood. We have begun to improve understanding in this area by examining simulated changes in precipitation, evaporation and snowpack in California. We are also examining this issue from an observational perspective. For example, we developed a comprehensive data set of monthly snow measurements in California's Sierra Nevada, and used the data to demonstrate that there have been advances in the timing of snow melt, even in areas where snowpack has been increasing.

Earth System Model Development

Underpinning all our Regional Climate Dynamics work is an active program of regional earth system model development, improvement, and validation. We have created modules to couple the regional atmospheric model WRF and the regional ocean model ROMS developed by Prof. Jim McWilliams, with biogeochemical modules developed by Prof. Curtis Deutsch. We've shown that this integrated atmosphere-ocean model produces realistic air-sea interaction and coastal circulation. In collaboration with Prof. Kuo-Nan Liou's group, we've developed a parameterization for solar fluxes in areas of intense topography, designed for regional models.  We are also working with Dr. Joao Teixeira's group to improve simulation of cloud in regional atmospheric models.  

Go to the Climate Feedbacks or Interdisciplinary research pages.