LAUSR

In this paper we outline a simple method to achieve mass conservation with Semi-Lagrangian based Limited Area Models (SL-LAM). Imposing mass conservation with LAMs requires knowledge of advective fluxes across their lateral boundaries. Estimation of these fluxes within a semi-Lagrangian scheme can be problematic. Aranami et. al. [1] have devised a method to achieve this, however, this requires extra interpolations which increase the computational cost of the model. By exploiting the way these models are designed and under some mild assumptions, a simple scheme is proposed that avoids computing the lateral fluxes altogether. The scheme achieves the same objectives as in [1] with minimal extra computational cost. This scheme is validated in a simple one-dimensional problem and then implemented in a full atmospheric model to show its effectiveness.