Ship-Board Atmospheric Sounding over the Kuroshio Extension: A Supplement to CLIVAR KESS

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The Kuroshio Extension (KE) is a region where the deep winter mixed layer allows locally and remotely forced subsurface variability to affect sea surface temperature (SST) on decadal and longer timescales. The Kuroshio Extension System Study (KESS) is a field experiment to "study the dynamic and thermodynamic processes governing the variability of, and the interaction between, the Kuroshio Extension and the recirculation gyre". While recent studies suggest that SST fronts in the KE region affect surface wind, cloud, atmospheric baroclinicity and storm track, few in-situ observations exist in this region that are necessary to test hypotheses regarding these ocean-atmospheric influences.The PIs will launch Global Positioning System sondes on the KESS cruises planned for May/June 2005 and 2006, acquiring vertical profiles of temperature, humidity, pressure and wind velocity. These observations, together with already funded KESS oceanographic component, will yield joint ocean-atmospheric transects of temperature and flow velocity from 1 km below the sea surface to 20 km above. Analysis of these field measurements combined with satellite observations will offer new insights into:(i) atmospheric boundary-layer adjustment to sharp SST fronts;(ii) the formation and variations of fog and stratus cloud deck north of the KE; and,(iii) ocean's role in maintaining the atmospheric storm track. The research expands the scope of KESS by adding atmospheric sounding that allows the study of KE's effect on regional climate. Shipboard GPS-sonde observations require little additional ship time, and the logistics and feasibility have been established in cruise surveys the PI and his collaborators successfully conducted over the region in the 2003-04 winter. The observations and analysis will improve our understanding of KE's influence on and interaction with the atmosphere. Broader impacts. The Meiyu-Baiu front is the most important climate phenomenon for East Asia. This research offers a better description and understanding of the ocean's role in formation and variations of this phenomenon, thereby helping enhance society's ability to plan and respond to its weather and climate. The resultant observational data, will be disseminated to the community via the KESS project website and the University of Hawaii (UH) Asian-Pacific Data Research Center's data servers. The research fosters interdisciplinary and international collaborations between oceanographers and meteorologists, and between US and Japanese scientists.