El Nino and Southern Oscillation (ENSO)

Markus Jochum (NCAR)

ENSO – a modeler's perspective

● What is ENSO?● Why use models?● What are the challenges?

NOAA/PMEL

NOAA/PMEL

NOAA/PMEL

NOAA/PMEL

NOAA/PMEL

Why models?

● Philosophical aspect: proof of understanding comes from reproducing/predicting

● Practical aspect: seasonal weather forecast provides societal benefits

● Desperation: for the foreseeable future there will not be enough observations to determine the nature of ENSO - ENSO triggered by noise - ENSO, an ocean-atmosphere oscillation

Lengaigne et al., 2004

Thermocline anomaly from CCSM3

CHALLENGE I: the observations

CHALLENGE II: What is the source of a bias in a coupled model?

CHALLENGE III: Physics

CHALLENGE IV: the global solution

Over long time periods like decades midlatitude oceanic biases will affect ENSO.

Surface wind stress fromT42x1 and ERS satellite

Summary

● Neither ignore nor trust the observations● ENSO is not a solved problem● Don't believe everything your advisor

tells you● There is no well defined ocean-

atmosphere boundary● If you cannot laugh about it, it is not the

right way!