A20YearAssessmentoftheFrequencyandIntensityof.pptVIP

A 20 Year Assessment of the Frequency and Intensity of McMurdo Area High Wind Events David M. Rasmussen Jr.1,*, Linda M. Keller1,2, and Matthew A. Lazzara1 Outline Motivation Defining a ‘high wind event’ Difficulties Results Conclusion Future Work Motivation Address hypothesis: Recent structural damage in the McMurdo region is do to an increase in the frequency, duration, and/ or intensity of ‘high wind events’ Use wind speed data from AWS stations in McMurdo/ Ross Island Region Spatial Variation Wind Event Thresholds Thresholds ~2 standard deviations from mean wind speed Choose nearest Beaufort Wind Force Scale Wind Distributions Beaufort Wind Force Scale Review Beaufort Scale cont. High Wind Event Duration Meets 6, 12, and 24-hour duration requirements At least half of observations from each high wind event must: not be missing meet Beaufort Force thresholds assigned to each AWS station Difficulties Too much missing wind data to make many clear assessments Difficulties cont. Results Little or no change in frequency of 6, 12, and 24 hour wind events between 1990’s and 2000’s at 3 AWS sites Results cont. Maximum wind speeds Two-tailored Student’s t-test used to determine changes in annual maximum wind speeds between 1990’s and 2000’s Results cont. Results cont. AWS wind speed direction Conclusion Slight increase in number of seasonal events at a few AWS sites seen between decades, but not significant Analysis heavily dependent upon quality of data, data availability seasons and years with greater than 25% missing data not included in analysis No significant change in high wind event frequency, duration and intensity seen across all sites between 1990’s and 2000’s, but analysis continuing Conclusion cont. No clear link between ENSO years and ‘high wind events’ Re-verification that the fewest frequency of events occurs in the Austral Summer Disagreement exists between other seasons as to which has the greatest frequency of ‘high wind events’ F