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Climatology and variability of atmospheric rivers over the north Pacific

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dc.contributor.authorMundhenk, Bryan D., author
dc.contributor.authorBarnes, Elizabeth A., advisor
dc.contributor.authorMaloney, Eric D., advisor
dc.contributor.authorRandall, David A., committee member
dc.contributor.authorHam, Jay M., committee member
dc.date.accessioned2017-09-14T16:05:24Z
dc.date.available2017-09-14T16:05:24Z
dc.date.issued2017
dc.description.abstractAtmospheric rivers (ARs) are plumes of intense water vapor transport that dominate the flux of water vapor into and within the extratropics. Upon landfall, ARs are a major source of precipitation and often trigger weather and/or hydrologic extremes. Over time, landfalling AR activity, or a lack thereof, can influence periods of regional water abundance or drought. An objective detection algorithm is developed to identify and characterize these features using gridded fields of anomalous vertically integrated water vapor transport. Output from this algorithm enables the investigation into the relationships between tropical variability and ARs over the North Pacific undertaken in this dissertation. In the first segment of this study, an all-season analysis of AR incidence within the North Pacific basin is performed for the period spanning 1979 to 2014. The variability of AR activity due to the seasonal cycle, the El Nino-Southern Oscillation (ENSO) cycle, and the Madden-Julian oscillation (MJO) is presented. The results highlight that ARs exist throughout the year over the North Pacific. In general, the seasonal cycle manifests itself as northward and westward displacement of AR activity during boreal summer, rather than a seasonal change in the total number of ARs within the domain. It is also shown that changes to the North Pacific mean-state due to the ENSO cycle and the MJO may enhance or completely offset the seasonal cycle of AR activity, but that such influences vary greatly based on location within the basin. The second segment of this study investigates ARs at high northern latitudes. Comparatively little is known about the dynamics supporting these ARs in contrast to their mid-latitude counterparts. ARs are found to occur near the Gulf of Alaska and the U.S. West Coast with similar frequency, but with different seasonality. Composited atmospheric conditions reveal that a broad height anomaly over the northeast Pacific is influential to AR activity near both of these regions. When a positive height anomaly exists over the northeast Pacific, AR activity is often deflected poleward toward Alaska, while the U.S. West Coast experiences a decrease in AR activity, and vice versa. This tradeoff in AR activity between these two regions applies across a range of time scales, not just with respect to individual transient waves. Both ARs and height anomalies are found to be associated with Rossby wave breaking, thereby dynamically linking the modulation of AR activity with broader North Pacific dynamics. The third segment of this study explores the predictability of anomalous landfalling AR activity within the subseasonal time scale (approximately 2-5 weeks). An empirical prediction scheme based solely on the initial state of the MJO and the stratospheric quasi-biennial oscillation (QBO) is constructed and evaluated over 36 boreal winter seasons. This scheme is based on the premise that the MJO modulates landfalling AR activity along the west coast of North America within the subseasonal time scale by exciting large-scale circulation anomalies over the North Pacific. The QBO is found to further modulate the MJO--AR relationship. The prediction scheme reveals skillful subseasonal "forecasts of opportunity" when knowledge of the MJO and the QBO can be leveraged to predict periods of increased or decreased AR activity. Moreover, certain MJO and QBO phase combinations provide predictive skill competitive with, or even exceeding, a state-of-the-art numerical weather prediction model.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.identifierMundhenk_colostate_0053A_14329.pdf
dc.identifier.urihttps://hdl.handle.net/10217/183961
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.subjectclimate variability
dc.subjectsubseasonal prediction
dc.subjectatmospheric river
dc.subjectteleconnection
dc.subject.lcshMadden-Julian oscillation
dc.titleClimatology and variability of atmospheric rivers over the north Pacific
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). 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).
thesis.degree.disciplineAtmospheric Science
thesis.degree.grantorColorado State University
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy (Ph.D.)

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