The Quantification of Co-occurring Meteorological Extremes and the Anthropogenic Contribution to Hydrometeorological Variation

• Main Author: O'Brien, John Patrick
• Other Authors: O'Brien, Travis A, Patricola, Christina P
• Format: Thesis
• Language: English
• Published: eScholarship, University of California 2019
• Subjects: Atmospheric sciences; Climate change; California; ENSO; hydrometeorology; Precipitation Variability; teleconnections; Ocean acidification
• Online Access: https://escholarship.org/uc/item/8fh4h62f; https://escholarship.org/content/qt8fh4h62f/qt8fh4h62f.pdf

It is a well-established fact that the present climate is changing as a result of human activities, the implications of which we are just now beginning realize. From record breaking heatwaves, wildfires, and extreme droughts, to sea level rise, ocean acidification, and severe flooding, there is little doubt that the consequences of anthropogenically driven climate change are wide and far reaching. One of the most confounding problems to date in understanding the effects of a changing climate is the absence of a world with a climate free from human interference to which to compare. The chaotic nature of atmospheric motions, naturally occurring low-frequency oscillations, and extreme events are all an inherent part of the climate system, and within that naturally occurring variability exists the signature of human interference with the global climate system. Thus the overarching aim of this dissertation is to describe, understand, and quantify the nature of extreme meteorological events in a climate subject to both natural and human induced forcings. In Chapter one, we employ a novel nonparametric probability density estimation method that allows for the characterization of nonlinear multivariant relationships among climatological variables. We develop and use this framework to quantify the multivariant relationships that exist between California wintertime temperature and precipitation as a function of naturally occurring low-frequency modes of variability to understand how they alter the probabilities for experiencing co-occurring extremes. Of the several modes studied, we find that a circumpolar Rossby wave of wave number 5 is uniquely capable of simultaneously driving both high temperatures and low precipitation thereby inducing or exacerbating antecedent drought conditions. Chapters two and three both employ two large ensembles of global climate model simulations. One ensemble is configured to represent the climate as it is today and the other configured to represent the best estimate of what the climate ...