Date of Award:

8-2018

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Advisor/Chair:

Simon S.-Y. Wang

Abstract

Global warming and climate change deeply influence weather and climate extremes, causing substantial property damage and loss every year around the world. Given the importance of heating differences between low-latitude and Arctic regions, which produce heat sources and cold sources that each influence global circulations, we investigate three extreme weather events in different regions in order to better understand the possible connections between extreme events and global circulation changes.

This study begins with climate variations in the low-latitude western North Pacific. In early summer, the timing of the wet season has shifted from late May to early June since 1979. This change influences the water supply in Southeast Asia. Our analysis results indicate that the increase in global temperatures is suggested to have induced this change. During the hurricane season, deep convection in the western North Pacific has a 20-year frequency of timing variations, oscillating between July and August and influencing hurricane activity. These variations have not been previously identified and do not have any driven forcings, but a precursor deep-convection signal is found in the spring.

Mid-latitude weather and climate can be influenced by tropical deep convection through the Pacific North American teleconnection. Our analysis results suggest that the wintertime Californian drought is mainly modulated by a teleconnection pattern from the tropics and natural variations in North Pacific circulation. Another key factor that influences mid-latitude circulation is Arctic temperature variations. We find an increase in the subseasonal Arctic warming event, suggesting more weather extremes in the mid-latitudes. Evidence suggests that sea-ice loss and the increase in tropical deep convection results in the increased likelihood of a subseasonal Arctic warming event.

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