Author/P.O.C.: Pleim, Computational Exposure Division, U.S. EPA
This change simplifies horizontal advection so that the ppm advection scheme (Colella and Woodward, 1984) is used sequentially for the X and Y directions in alternating order without the densiity weighting adjustment that was formerly used in the so-called "yamo" scheme.
Removed the adjustment to horizontal velocities for the second component of horizontal advection by the ratio of initial air density / x or y component advected density. This was intended to partially correct for cross term errors when using alternating 1-D advection. Now, rather than x-ppm followed by y_yamo and y_ppm followed by x_yamo, we have x-ppm then y ppm and y_ppm then x_ppm
Advantage is that it is now positive definite (no more floor files) and it is robust for changes in domain decomposition. Disadvantage is that there may be greater cross-term errors that could induce small lumpiness.
CCTM/src/hadv/ppm/hadvppm.F CCTM/src/hadv/ppm/advbc_map.F CCTM/src/hadv/ppm/hcontvel.F CCTM/src/hadv/ppm/hppm.F CCTM/src/hadv/ppm/rdbcon.F CCTM/src/hadv/ppm/x_ppm.F CCTM/src/hadv/ppm/y_ppm.F CCTM/src/hadv/ppm/zfdbc.f
Colella, P., & Woodward, P. R. (1984). The piecewise parabolic method (PPM) for gas-dynamical simulations. Journal of computational physics, 54(1), 174-201.