Climate predictability affected by and resulting from internal variability

Within this objective we focus on internal climate dynamics and variability, with respect to both limits of predictability originating from unpredictable fluctuations (led by Jin-Song von Storch), and predictability originating from slow climate components (in collaboration with CRG Baehr).

For the efforts lead by Jin-Song von Storch, AMIP-style simulations with ECHAM6 at different horizontal resolution (T63L95, T127L95, and T255L95) are used to quantify the impact of small-scale fluctuating components on large-scale states. With increasing resolution the simulated climate is, when measured by a global measure, closer to the reanalysis with respect to the mean state and the variance (Dahms et al., 2014), especially in the extra-tropics. Also, stratospheric variability is stronger influenced by the horizontal resolution than the troposphere. Major challenges remain the simulation of the precipitation and climate features like the MJO, which might require a coupled atmosphere-ocean model.

Participating team members:
Jin-Song von Storch, Eileen Hertwig, Johanna Baehr, Daniela Domeisen.

Magnitudes of the mean (bottom) and fluctuating (top) components of the divergences of oceanic eddy heat fluxes at 2000 m in the 1/10 degree STORM ocean-only simulation (Li and von Storch, JPO, 2013). Previous studies on meso-scale eddies have been concentrated mainly on the mean component of the eddy fluxes. We show for the first time that fluctuations around the mean are of one order of magnitude stronger than the mean eddy fluxes. These fluctuations are expected to significantly affect the general circulation and its variability. More over, the result suggests that meso-scale eddies have to be parametrized using a stochastic, rather than a purely deterministic, scheme.