When? February 19, 2025 at 12:00 UTC (13:00 CET)
Where? GoTo Meeting App - Link
NOTE THIS WEBINAR WON'T BE RECORDED.

2.The second edition of CLIVAR Tropical Basin Interaction Research Focus Webinar Series: El Niño Southern Oscillation and Tropical Basin Interaction in Idealized Worlds by Dr. Dietmar Dommenget (Monash University).

When? March 5, 2025 at 22:00 UTC 
Where? GoTo Meeting App - Link

You can watch the recording here.

Abstract

In this study we discuss a set of GFDL coupled general circulation model simulations with idealised geometries of the tropical ocean basins and land with a focus on important characteristics of El Niño Southern Oscillation (ENSO) type of variability and tropical basin interaction. In a series of 15 simulations, we first vary the zonal width of a single tropical ocean basin from 50 to 360 degrees, while the rest of the tropical zone is set as land. Further we discuss different simplified configurations of two or three tropical ocean basins. The results show remarkable changes in ENSO characteristics as a function of basin width and due to the interaction with other basins that challenge our current understanding of ENSO dynamics. The results suggest that atmospheric dynamics are largely controlling ENSO dynamics. We will discuss shallow water atmosphere (Gill-type) model results to explore how simplified atmospheric dynamics can control growth rate (Bjerknes feedback) and period of ENSO.

Dietmar Dommenget (Monash University)

Associate Professor Dietmar Dommenget completed his Diploma (MSc) in Physics at the University of Hamburg. He started studying climate dynamics and climate model development at the Max Planck Institute for Meteorology in 1996 and finished his PhD in 2000. A/ Prof Dommenget joined the Estimating the Circulation and Climate of the Ocean project in a postdoctoral position at the Scripps Institution of Oceanography in La Jolla, California, to study the predictability of El Niño with an adjoint data assimilation scheme. After three years in California he returned to Germany, in 2003, for a fixed-term faculty position as a junior professor (lecturer) in the meteorology department at the GEOMAR Helmholtz Centre for Ocean Research, Kiel. Since 2010, he has been at Monash University in the atmospheric and climate science group of the School of Earth, Atmosphere and Environment. A/Prof Dommenget’s research focuses on large-scale climate dynamics and climate modelling. He works with climate models at all levels of complexity, with most of that work being centred on the development, conducting and analysis of coupled general-circulation models. He has also developed simple conceptual models of natural climate variability. Much of A/ Prof Dommenget's research focuses on sea-surface temperature variability in the tropical and extratropical oceans, and he is also known for his work on the interpretation of patterns and modes of climate variability. Recent projects focus on El Niño, climate model developments and climate change. A/ Prof Dommenget developed a new type of climate model for the conceptual understanding of the climate response to external forcing, which is a fast and simple tool for researchers, students and the public to understand the interactions in the climate system. An outreach program based on this is called the Monash Simple Climate Model.

3.The third edition of CLIVAR Tropical Basin Interaction Research Focus Webinar Series: Understanding Extreme Climate Events: 2023-24 El Niño, Hottest Years, and More by Dr. Shang-Ping Xie (Scripps/UCSD).

When? April 24, 2025 at 00:00 UTC 
Where? GoTo Meeting App - Link

You can watch the recording here.

Abstract

2023 was the hottest year on record by then for global-mean temperature, beating the previous instrumental record by a large margin. The year opened with extreme ocean warming, heavy rainfall, and an unprecedented cyclone Yaku off the Peruvian coast in March. A strong basin-scale El Niño then developed. This El Niño event was unusual for its combination of strong oceanic warming but muted atmospheric responses, particularly in terms of the Southern Oscillation and wind anomalies over the tropical Pacific. This discrepancy is perplexing given the historically close coupling of El Niño and the Southern Oscillation. We ask two mutually related questions: 
Meteorologically, why were the zonal wind anomalies weak over the equatorial Pacific in 2023 despite a growing El Nino? Atmospheric model simulations show that sea surface temperature anomalies in other ocean basins suppress the Southern Oscillation, indicating the importance of trans-basin interactions. 
Oceanographically, how did El Nino grow despite the lack of zonal wind anomalies over the tropical Pacific? A novel hindcast system we developed for equatorial ocean variability shows that the strong buildup of ocean heat content in the western Pacific associated with the preceding prolonged La Niña caused the growth of El Niño warming through wave dynamics and thermocline feedback, even without wind stress feedback during much of 2023. 
Each El Niño is different. Scrutinizing each unique El Niño will deepen and enrich our understanding of tropical variability and predictability.