The HyperCASL algorithm

This paper outlines a major new extension to the diabatic Contour-Advective Semi-Lagrangian (CASL) algorithm [5; 8]. The extension, called the 'HyperCASL' (HCASL) algorithm, advects material potential vorticity contours like in CASL, but treats diabatic forcing or damping with a Vortex-In-Cell (VIC) algorithm. As a result, HCASL is fully Lagrangian regarding advection. A conventional underlying grid is used as in CASL for 'inversion', namely for obtaining the advecting velocity from the potential vorticity.</p