Using an antidiffusive transport scheme in the vertical direction: a promising novelty for chemistry-transport models

Abstract

Abstract. The potential interest of the antidiffusive transport scheme proposed by Després et Lagoutière (1999) for resolving vertical transport in chemistry-transport models is investigated in an idealized framework with very encouraging results. We show that, compared to classical higher-order schemes, the Després et Lagoutière (1999) scheme reduces numerical diffusion and improves accuracy in idealized cases that are typical of atmospheric transport of tracers in chemistry-transport models. Increased accuracy and reduced diffusion is spectacular when, and only when vertical resolution is insufficient to properly resolve vertical gradients, which is very frequent in chemistry-transport models. Therefore, we think that this scheme is an extremely promising solution for reducing numerical diffusion in chemistry-transport models.

The CHIMERE v2020r1 online chemistry-transport model

“…Implementation of the Després and Lagoutière (1999) scheme in CHIMERE is discussed in detail in Lachatre et al (2020), which shows the strong reduction in vertical diffusion obtaine with the use of this scheme relative to Van Leer (1977). Mailler et al (2021) discusses in more detail the strength and weaknesses of this scheme relative to Van Leer (1977).…”

Review of Review of “Using an antidiffusive transport scheme in the vertical direction: a promising novelty for chemistry-transport models”

“…2. It seems like an oversight to not invoke Godunov's theorem (Godunov, 1959), especially on lines 306-308. It is a known result that any higher-order scheme cannot exceed first-order accuracy in the vicinity of a sharp gradient, so it is not true that "higher-order schemes are expected to reduce numerical error at any given resolution".…”