Abstract
In atmospheric modeling, superparameterization has gained popularity as
a technique to improve cloud and convection representations in large
scale models by coupling them locally to cloud-resolving models. We show
how the different representations of cloud water in the local and the
global models in superparameterization lead to a suppression of cloud
advection and ultimately to a systematic underrepresentation of the
cloud amount in the large scale model. We demonstrate this phenomenon in
a regional superparameterization experiment with the global model
OpenIFS coupled to the local model DALES (the Dutch Atmospheric Large
Eddy Simulation), as well as in an idealized setup, where the
large-scale model is replaced by a simple advection scheme. To mitigate
the problem of suppressed cloud advection, we propose a scheme where the
spatial variability of the local model’s total water content is enhanced
in order to achieve the correct cloud condensate amount.