Rossby waves propagating along the extratropical tropopause have a dominant impact on weather at the surface in midlatitudes via baroclinic instability. While forecasts of waves by numerical weather prediction systems are limited by intrinsic unpredictability due to initial condition sensitivity, the statistical properties of these features should not contain biases if the models are optimally designed. In this study, statistical properties of upper level waves in forecasts are evaluated for the seasons 2008-2012. Wavelet transforms are used to analyze Rossby wave amplitude as a function of both wavelength and longitude. The wavelet transforms are applied to both analysis and forecast potential vorticity. The difference between the two reveals model error. This process is done for three operational centers: ECMWF, UKMET, and NCEP, over 5 winter seasons. A comparison is made of 5 dependencies: forecast center, interseasonal variation, longitude, lead time, and wavelength. Additionally, a wave breaking diagnostic is developed as a supplemental tool for determining wave structure errors in operational models. Breaking frequency determines how many points of longitude in the wave pattern on average per day were breaking. The analysis reveals: 1) On average, Rossby wave amplitude is under forecast in all 5 dependencies, statistically significant at the 95% confidence level, 2) The largest errors are found in regions of climatologically higher wave activity, 3) errors in ECMWF are smaller and accumulate more steadily than UKMET and NCEP, which demonstrate large error very early in forecasts, 4) The errors represent biases in the model, not a regression to the mean, and 5) There are large errors in the wave breaking frequency for all forecast centers. The results imply an inherent issue in operational models with forecasting wave amplitude. How the errors vary across the 5 dependencies and how the work may be expanded for further study are discussed. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester, 2015. / March 5, 2015. / analysis, forecast, model, Rossby wave, tropopause, wavelet / Includes bibliographical references. / Jeff Chagnon, Professor Directing Thesis; Robert Hart, Committee Member; Ming Cai, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_253063 |
| Contributors | Wilkerson, Justin (authoraut), Chagnon, Jeffrey M. (professor directing thesis), Hart, Robert E. (Robert Edward), 1972- (committee member), Cai, Ming, 1957- (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Earth, Ocean, and Atmospheric Science (degree granting department) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (38 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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