The importance of vertical resolution in the free troposphere for modeling intercontinental plumes
Year: 2018
Type: article
Abstract: . Chemical plumes in the free troposphere can preserve their identity for more than a week as they are transported on intercontinental scales. Current global models cannot reproduce this transport. The plumes dissipate too rapidly due to numerical diffusion in sheared flow. We demonstrate how model accuracy can be limited by either horizontal resolution (Δx) or vertical resolution (Δz). Balancing horizontal and vertical numerical diffusion, and weighing by computational cost, implies an optimal grid resolution ratio (Δx/Δz)opt ~ 1000 for plume transport. This is considerably higher than current global models (Δx/Δz ~ 20) and explains the rapid plume dissipation in these models as limited by vertical resolution. Plume simulations with the GFDL-FV3 global dynamical core over a range of horizontal and vertical grid resolutions confirm this limiting behavior. Our highest-resolution simulation (Δx ≈ 25 km, Δz ≈ 80 m) preserves the maximum volume mixing ratio in the plume to within 35 % after 8 days in strongly sheared flow, a drastic improvement over current models. The local surface pollution influence from the subsiding plume on intercontinental scales is also considerably increased. Adding free tropospheric vertical levels in global models is computationally inexpensive and would also improve the simulation of water vapor.
Institutions: Harvard University, Massachusetts Institute of Technology
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,725
OpenAlex ID: W2774107808