Extratropical cyclones (ETCs) are a common feature of mid- and high-latitudes which, on a large scale, are a primary mechanism by which heat and moisture are transported from equator to pole. ETCs also exert a major impact at smaller scales. Communities along the western coast of Alaska face many types of impacts generated by the winds associated with ETCs, including storm surges, sea water intrusion into fresh water stores, and coastal erosion. Such “strong wind events”, which can occur independent of an ETC, can also generate hazardous sea states and associated impacts on shipping. With no roads, coastal Alaska relies heavily on marine and air transportation. Hazards posed to marine and air travel are often related to two main types of weather: wind and fog. Consultations with stakeholders in the marine transportation community have indicated more precisely specific aspects of poor weather, such as high wind events, that are problematic, including the idea that the periods between strong wind events, defined as lull periods, represent an important metric when planning travel between points of safe harbour.
Three separate studies of storminess metrics in the North Pacific and Alaskan regions are presented. The first study presents both a comparison of two storm identification and tracking algorithms and an evaluation of the general characteristics of extratropical cyclones for the North Pacific as portrayed in two reanalyses. The second study applies a modified wind event identification algorithm to reanalysis data to evaluate the spatial climatological patterns of wind events in the circum-Arctic. The third study tests the statistical relationships and predictability of two measures of storm activity - cyclone track density (TDEN) and wind event frequency - in the North Pacific using teleconnection indices exhibiting local influence. The first study showed that the general patterns and trends of cyclone characteristics are similar between the two methods, though with increased values of cyclogenesis density, cyclolysis density, and track density when using the relative vorticity based method. A comparison between storm tracks for NCEP1 and the 56-member ensemble of the Twentieth Century Reanalysis v2 (20CR) shows distinct differences between the 20CR and NCEP1 mean climatology for main storminess indicators. The second study evaluated the spatial and temporal characteristics of wind events and introduced a novel indicator that characterizes periods of favorable weather between strong wind events that last 48-hours or longer, termed lull events. Lull periods were found to be an important consideration for northern marine operations – both economic and subsistence. Additionally, combinations of lull and wind event indicators, termed lull/storm winds (LSW), were analyzed and showed that preferred areas of wind events and lull events are not always spatially coherent. The third study tested the statistical relationships and predictability of two measures of storm activity - cyclone track density (TDEN) and wind event frequency - in the North Pacific using teleconnection indices with local influence for the winter period of 1950 - 2012. Two statistical modeling techniques are applied to evaluate linear and non-linear methods of prediction for the region. For both measures of storm activity, the North Pacific index, Niño 3.4 index, and the AO index were found to be the best predictors. Using a 23-year hindcast period (1980 – 2012), the region of highest wind event anomaly prediction skill is located in the western Bering Sea, with hindcast correlation values as high as +0.5 and root mean squared skill scores (RMSESS) 25% higher than climatology. Highest TDEN predictive skill from the 23-year hindcast is found in the southeast region of the North Pacific, near the California coastline, with correlation and RMSESS as high as +0.7 and 25 - 30%, respectively. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/7519 |
| Date | 02 September 2016 |
| Creators | Shippee, Norman |
| Contributors | Atkinson, David |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web, http://creativecommons.org/licenses/by-nc-nd/2.5/ca/ |
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