Extended Abstract (928K)7B.5
Impacts of Air-Sea Fluxes on the Evolution of an Arctic “Bomb”
Lujun Zhang, Nanjing University and Bedford Institute of Oceanography, Dartmouth, NS, Canada; and W. Perrie and Z. Long
The Arctic is a significant region for because of its unique thermodynamic characteristics and its potential role in global climate change. Intense Arctic storms are examples of "extreme" weather which can has impact on coastal oceanographic processes in the southern Beaufort Sea and waters of the west Canadian Arctic. This area is important because the coastal marine environment used by Canadian Northerners is an integral part of their life style. The area is also undergoing hydrocarbon exploration with potential development within the next decade. Factors such as open water and ice, and the oceanic surface fluxes can modulate storm development and winds. Climate change in the Beaufort-Chukchi region may endanger coastal settlements and marine environments.
In tropical and extratropical latitudes, it is well known that hurricane intensity is influenced by factors such as the storm's initial intensity, the spatial extent of the storm, the thermodynamic state of the atmosphere through which the storm moves, the storm propagation speed, and sea surface fluxes along the storm track. Although several of these factors are also known to modulate the strength of midlatitude cyclone systems, little is known about the impact of atmosphere–ocean–ice interactions on storms in the Arctic Ocean. In this study we investigate the ability of surface heat fluxes to influence Arctic storm development, including processes that control their atmosphere–ocean–ice dynamics. We use the Canadian Mesoscale Compressible Community (MC2) atmospheric model coupled to the Princeton Ocean Model (POM) and Hibler Ice Model.
As a case study we simulate an Arctic storm from late 1999. Comparing our results to NCEP, NARR and CMC reanalysis data, we demonstrate very good simulations of the storm pattern, track and intensity. This cyclone is a mesoscale Arctic storm that developed over the NE Pacific and western Bering Sea. It intensified explosively in the Gulf of Alaska, developing into a meteorological bomb on 21 September 1999. The storm made landfall with surface winds > 30 m s-1 at Cape Newenham, Alaska, on 22 September and rapidly moved north northeastward. Thereafter, it crossed the Rocky Mountains to the Yukon and Northwest Territories and re-intensified over the coastal waters of the southern Beaufort Sea, over a zone of high sea surface temperature gradients, causing extensive coastal damage to communities in that region. During with its mature stage, satellite images reveal mesoscale scale and spiral cloud bands of unusual symmetry. The track of the low pressure center passed over Anchorage, Alaska where time series show a pronounced maximum in equivalent potential temperature at the storm's core.
We show the role of sea surface fluxes on the storm's explosive development as a bomb in the NE Pacific and in its re-intensification over the Beaufort coastal waters. We compare these processes to the other factors that modify the storm's development as it passes from the generation region in the Pacific, across the Rockies, to its final decay region in the Arctic.
Session 7B, High-latitude air-sea interaction
Tuesday, 13 January 2009, 3:30 PM-5:15 PM, Room 128B
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