  We present a simple finite element formulation of mass-consistent
approximation, and a fast multigrid iterative method with adaptive
semicoarsening, which maintains the convergence of the iterations over a range
of grids and penalty coefficients. The method is designed to run in each time
step of WRF-SFIRE and replace the interpolation from the atmospheric mesh to
the fire mesh by a diagnostic model of the air flow over a fine-scale terrain.

Numerical Analysis;Numerical Analysis;Atmospheric and Oceanic Physics