Hawaiian Winter Rainfall Variability during Central Pacific (CP) and Eastern Pacific (EP) El Niño Events.

dc.contributor.author Bai, Xiaoyu
dc.contributor.department Atmospheric Sciences
dc.date.accessioned 2019-05-28T19:33:18Z
dc.date.available 2019-05-28T19:33:18Z
dc.date.issued 2017-08
dc.identifier.uri http://hdl.handle.net/10125/62188
dc.title Hawaiian Winter Rainfall Variability during Central Pacific (CP) and Eastern Pacific (EP) El Niño Events.
dc.type Thesis
dcterms.abstract Historically, Hawaiian winter (December through February) rainfall is known to be drierthan- normal during El Ni~no events due to the eastward shift in the subtropical jet stream core over the North Paci c and enhanced sinking motion associated with the local Hadley circulation over the central Paci c. Recent studies suggest that El Ni~no can be broadly separated into two types: (1) Eastern Paci c (EP) El Ni~no which has its largest sea surface temperature (SST) anomalies centered in the equatorial eastern Paci c, and (2) Central Paci c (CP) El Ni~no which has its largest SST anomalies centered in the equatorial central Paci c. When considering El Ni~no events according to these two types, is Hawaiian winter rainfall still drier-than-normal? This study rst compares precipitation records between 1957 to present of 21 stations from Kauai, Oahu, Maui and Hawaii during the two types of El Ni~no winters. Results show that all stations are wetter during CP winters than EP winters. Comparison between EP, CP winters and climatology shows that during EP El Ni~no winters the Hawaiian Islands have a drier-than-normal precipitation pattern, while during CP El Ni~no winters the Hawaiian Islands have a normal precipitation distribution and, for some stations, slightly wetter-than-normal precipitation anomalies. To nd the mechanisms behind these rainfall anomalies during CP and EP winters, further analysis is on the subtropical jet stream, horizontal wind eld, vertical velocity, outgoing longwave radiation, speci c humidity, and moisture transport. Dynamical downscaling using Advanced Research Weather Research and Forecasting (WRF-ARW) model is adopted to show a detailed wind eld distribution and rainfall simulation. The Hawaiian Rainfall Atlas, which is a set of high resolution Hawaiian rainfall maps, is also analyzed to show spatial rainfall anomalies during the two types of El Ni~no. Although more research needs to be done, the hypothetical contributions to the wetter conditions on the Hawaiian Islands during CP winters as compared to EP winters are: lower level southwesterly wind anomalies, weaker descending motion over the Islands, and positive speci c humidity anomalies over the Islands.
dcterms.description M.S. Thesis. University of Hawaiʻi at Mānoa 2017.
dcterms.language eng
dcterms.publisher University of Hawaiʻi at Mānoa
dcterms.rights All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
dcterms.type Text
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