The resolution dependency of atmospheric blocking in the aqua-planet experiments

Abstract:

Quasi-stationary planetary waves forced by topography or other zonally asymmetric features are usually suggested to be essential for blocking formation; however, we found the 2-D feature of blocking could also occur frequently without these precondition.

In a set of aqua-planet simulations with setting of perpetual spring, the blocking feature is identified through a combination of meridional height gradient and 2-D height anomaly. The general distribution resembles the Pacific blocking, but more equatorward. The resolution sensitivity experiment suggests that, associated with the poleward shift of the subtropical jet stream, the blocking activity also moves northward with higher resolution, and converges between 60km and 30km. The blocking with finer resolution also shows a more realistic characteristic timesale. By utilizing the wave activity budget analysis, it is found that, in the decay stage, the effective diffusivity would be much larger, thus the blocking waves are absorbed more efficiently by the mean flow.