Part 1. Changes in Madden-Julian Oscillation Activity and Easterly Waves in a Warmer Climate Using CESM2, and Part 2. The Strength and Impacts of Atmospheric Rivers in the HENS Model Using TECA-BARD
Amanda Bowden, University of Colorado Boulder
Part 1. Easterly waves (EWs), are one of the precursors to tropical storms, which are among the deadliest and costliest weather phenomena due to their coastal hazards. Other disturbances, such as the Madden-Julian Oscillation (MJO), make conditions favorable for hurricane spin-up by creating periods of anomalous westerly winds that are associated with enhanced cyclonic flow, moisture, precipitation, and EW activity. The MJO is expected to become stronger in a warmer environment, which could cause its modulation of EWs to become stronger with increased effects on vulnerable communities. This investigation uses the CESM2 Large Ensemble to examine the frequency and intensity of EWs and their modulation by the MJO. This study examines how the frequency and intensity of EWs will change in a future (warmer) climate, including whether their relationship to MJO activity changes. Initial results suggest a general decrease in EW activity across the tropics with warming.
Part 2. Atmospheric Rivers (ARs) are long, narrow bands of water vapor from the tropics to the poles, and are severe enough to cause loss of life and property damage. CASCADE4 research advances understanding of climate extremes known as low-likelihood, high-impact events (LLHIs) such as ARs that are unanticipated, anomalous events that have strong impacts on the public, especially with climate change. This investigation uses machine learning (ML) emulators called FourCastNet to generate such massive ensembles called Huge Ensemble Members (HENS). ARs from these traditional numerical simulations are identified through Toolkit for Extreme Climate Analysis (TECA) Bayesian AR Detector (BARD), which encompasses AR counts, spatially filtered versions of the Integrated Vapor Transport (IVT) magnitude, and probability of AR detection. The severity of the detected AR in the HENS is further categorized from 1 through 5, which are defined by maximum IVT thresholds, while the 24-hour duration determines whether being recategorized.