Date of Award

12-23-2008

Document Type

Restricted Access Thesis

Degree Name

Master of Science in Applied Meteorology

Department

Department of Atmospheric Sciences and Chemistry

Thesis Advisor

Lourdes Aviles

Committee Member

Thomas Boucher

Committee Member

James Koermer

Abstract

Extensive research has been performed on the correlations between El Niño and La Niña events and the associated decrease and increase in Atlantic basin tropical cyclone activity. However, Neutral seasons have been found to be on average near the climatological norm in Atlantic tropical cyclone activity, and hence have not been a focus of study. This work shows that much as there are different types of El Niño and La Niña events (e.g. weak, moderate, strong), there are different types of Neutral events as well when one categorizes them based upon the net change in equatorial Pacific SST anomaly over the course of the Atlantic Hurricane Season. When these discrete phases are analyzed for tropical cyclone activity and atmospheric teleconnection, it can be shown that they too have distinct patterns of tropical cyclone activity that deviate significantly from the climatological norm. Specifically, neutral seasons where small scale warming (termed Tending El Niño) events occur are found to have markedly decreased Atlantic tropical cyclone activity in terms of net storms, accumulated cyclone energy, United States landfall frequency and United States landfall intensity. Conversely, neutral seasons where small scale cooling (termed Tending La Niña) events occur are found to have markedly increased Atlantic tropical cyclone activity in terms of those same parameters. Overall, it is found that ENSO Neutral seasons can and do have significant impacts on the atmospheric conditions that modulate Atlantic tropical cyclone activity and should be seen as just as important as the more well known El Niño and La Niña ENSO phases.

Share

COinS