2025 Theses Doctoral

Methodologies for Identifying and Understanding Cross-timescale Interference & The Exposure, Use, and Trust of Climate Information in Colombia

DiSera, Laurel

The research presented here is driven by the fundamental question, how does cross-timescale interference impact climate and society? The topic of cross-timescale interference is still relatively new in the literature and identifying new methods for evaluating such interferences will contribute to a deeper understanding of climate physics and allow for the improvement of climate models, enabling better prediction of the climate. Additionally, as new climate tools and more accurate forecasts are produced and becoming available to farmers, there is an ever-growing need to understand what tools are used or needed by communities to help identify changes in climate, such as cross-timescale interference.

This dissertation comprises four chapters assessing these two knowledge gaps and contributes to the frontier of creating methodologies to understand cross-timescale interference.The first chapter analyzes the cross-timescale interference observed between ENSO and the MJO and compares the resulting rainfall composites to the 2015-2016 and 1997-1998 El Niño events, with the goal to identify if cross-timescale interference is visible in these two particular events. Results from Chapter 1 conclude that it is possible to identify cross-timescale interference between ENSO and the MJO through the use of compositing techniques and find that the contribution of cross-timescale interference varies based on ENSO event.

The second chapter follows closely to the first, utilizing the same compositing techniques to produce rainfall composites, but focuses on the question of if and where the cross-timescale interference is linear or nonlinear. Adding to the conclusions of Chapter 1, Chapter 2 finds that it is possible to tease apart the linear and nonlinear contributions of cross-timescale interference, showing greater nonlinear interference during the 2015-2016 El Niño event than the 1997-1998 El Niño event.

The third chapter is a case study of the 2020-2023 La Niña event that identifies whether or not climate driver interaction played a role in the formation and persistence of the three year long La Niña event. Chapter 3 concludes that the MJO interacted with the Indian Ocean Dipole (IOD) in late April and early June of 2019 to trigger a strong positive IOD event, which contributed to the onset of the three year-long La Niña event experienced from 2020-2023.

The fourth chapter of this dissertation underscores the importance of field work to contextualize the work of climate scientists. Specifically, the research focused on the specific needs, trust in, and uses of climate information and services by farmers in rural Columbia. Chapter 4 concludes that farmers in Colombia still do not use or trust many of the climate services available to them, especially small farmers and coffee growers. However, through the use of local round table discussions (MTAs), rice farmers in northern Colombia have better utilized and incorporated climate information into their farming practices.