Decoding ENSO Diversity: Examining the Eastern and Central Pacific Phases, Remote Responses, and Hydrological Effects

The El Niño Southern Oscillation (ENSO) is a pivotal and variable climate pattern resulting from complex ocean-atmosphere interactions. These interactions significantly influence weather, climate, ecosystems, and economies, leading to events such as droughts, floods, hurricanes, and wildfires. This study explores the different signals of ENSO and classifies individual events by phase while seeking to decode remote responses in Water Vapor (WV) and Precipitation. ENSO events vary in their presentation and impacts, both spatially and temporally, exhibiting two primary phases: El Niño (EN) and La Niña (LN), corresponding to its warm and cold phases, respectively, and two subcategories: Eastern Pacific (EP) and Central Pacific (CP). The EP subcategory represents the canonical depiction of ENSO, characterized by warm or cold tongues of water, while the CP subcategory features heating or cooling centered in the Pacific. The increasing frequency CP ENSO events necessitates enhanced classification and further research into their distinct seasonal hydrological and microclimatological impacts. Variability in SST can lead to larger scale changes in variables such as WV and Precipitation, which are major components of Atmospheric Rivers (ARs). In the United States, ENSO phases can affect the frequency and intensity of ARs, with El Niño often enhancing AR activity in the southwestern United States, while La Niña shifts AR patterns towards the Pacific Northwest. There is a need to identify how ARs respond to each subcategory (EP/CP) for both ENSO phases as improved predictability is crucial for mitigating ENSO-related teleconnections and enhancing resilience against their diverse and regional impacts.