Tropical climate and variability (Madden Julian Oscillation)

The Madden and Julian Oscillation (MJO) is the dominant mode of intraseasonal variability (ISV) in the tropics with considerable convective precipitation systems propagating eastward from the Indian Ocean towards the West Pacific and decaying near the date line. GCMs evince considerable shortcomings in simulating the MJO. However, the climate model of the Max Planck Institute for Meteorology (ECHAM) produces a relatively good simulation of the MJO relative to other climate models.

This can be seen in the figures below. On the left hand side are the results for the simulation with ECHAM6/MPI-OM (T127L95 atmosphere version and TP04 ocean version), on the right hand side the observations for a 20-year period. Shown are the mean 8 phases if the life-cycle of the MJO. The colors represent the outgoing longwave radiation (OLR), which is a measure for deep convection and deep convective precipitation. The blue colors represent negative OLR anomalies, representing enhanced deep convection. The orange colors represent positive OLR anomalies, representing suppressed deep convection.Obviously, the main characteristic of the life-cycle is well captured, however, on the whole, convection is still underestimated.

 

        

 

The MJO performance of a climate model depends on the convection scheme, but also on model resolution, and whether or not the simulations are coupled to an ocean model. Recent studies further suggest that MJO skill is related to a larger mean state bias and vice versa. Among other things, we investigate this by using a multitude of simulations with various versions of ECHAM.

 

Further research interests:

  •  Climate modelling
  •  Simulation of artificial tree rings from climate model data
  •  Ocean carbon cycle