Collaborative Research: Barrier Jets in the Gulf of Alaska - Causes, Impacts, and Interactions with Other Phenomena

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The mesoscale atmospheric flow near coastlines with prominent terrain has a tremendous impact on those who live and work in the coastal environment. Yet this class of localized wind systems remains a challenging and important problem in weather prediction. One of the most common terrain-induced coastal flows, the barrier jet, creates especially dangerous weather conditions, particularly in southeast Alaska and the Pacific Northwest. The resulting severe winds pose a threat to life, property, and economic activities. Addressing these societal issues requires research to improve understanding of the dynamics of coastal barrier jets and the larger-scale weather conditions required for their formation. Recent advances in satellite remote sensing technology provide an opportunity to further understanding of barrier jets. For example, synthetic aperture radar (SAR) provides detailed measurements of the surface wind speed with resolutions of hundreds of meters over regions several hundred kilometers on a side. Moreover, with SAR the wind speed field can be observed to within 1 km of the coastline. These SAR speed observations can be combined with other observations and model output to provide high-resolution wind vector maps throughout the coastal zone. These SAR-derived wind maps from several thousand cases over the past 5 years, archived at the Johns Hopkins University Applied Physics Laboratory, represent a unique resource for the development of improved understanding of barrier jets along the Alaskan coast. This archive contains on the order of 100 cases of barrier jet flows over the Gulf of Alaska. In this project, the Principal Investigators will exploit this archive, along with additional imagery, in situ observations and numerical simulations to gain a greater understanding of the dynamics of barrier jets along the western coast of North America and of the larger-scale weather conditions required for their formation, thereby providing the basis for operational forecasting of this hazardous phenomenon.Additionally, the interactions between the flow associated with barrier jets and local ocean circulations will be investigated. The barrier jet climatology will be used to map the seasonal mean wind stress anomalies associated with barrier jets in the Gulf of Alaska. These wind stress anomaly maps will be used to determine the mean Ekman pumping associated with barrier jets and the resulting upper ocean response. These results well be checked against in situ observations from moored buoys and used to examine the impact of barrier jets on the marine ecosystem. These findings will provide important information to the fisheries industry as well as the marine biology and physical oceanography research communities.