The 7^th telecon of ENSO Conceptual Model Working Group was organised on 17 June, 2021 (June 16 for some participants).

At the beginning of the telecon, Jerome Vialard, the coordinator of the working group, briefly introduced a session proposal entitled ‘El Nino in a Changing Climate’ submitted to the 2022 Ocean Science Meeting (Hawaii, Feb. 27 – Mar. 4, 2022). The session is a generalist ENSO session with a focus on ENSO conceptual models, achieved through invited contributions on this topic and a coordinated “tutorial” (accessible review talk) by F-F. Jin and C. Wang. It will be co-convened by four members of the working group, i.e. Jerome Vialard, Samantha Stevenson, Malte Stuecker and Andrew Wittenberg. Meanwhile, a face-to-face meeting for the ENSO Conceptual Model WG is being planned at the University of Hawaii, with the goal to develop the outline of the ENSO Conceptual Model review paper, emphasizing on the way forward.

Then, a one-hour talk was given by Fei-Fei Jin on an overview of the recharge oscillator (RO) ENSO conceptual models, and how they represent ENSO properties and the scope for improvement. According to Fei-Fei, the lowest order RO (RO-2) is a minimum unified framework for almost all the conceptual model based on solid physical, mathematical and conceptual consideration for understanding the basic features of ENSO, including the growth rate and frequency; phase-locking; warm/cold asymmetry as well as the amplitude of ENSO. However, RO-2 cannot represent the pattern diversity, and does not account for the Gravest Basin Mode Oscillation (GBMO) dynamics which may allow to represent some aspects of the ENSO development and phase transition better. Participants actively discussed the robustness as well as the missing ingredients of the RO hypotheses.

The next telecon will be organised on 1 July 2021, focusing on how the delayed, advective-reflective and western Pacific oscillators account for ENSO properties. A talk will be given by Dr. Chunzai Wang.