Sensitivities of parcel trajectories beneath the lowest scalar model level of a Lorenz vertical grid

Andrew Vande Guchte, Johannes M.L. Dahl

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Parcel trajectory analysis has become commonplace in the study of simulated severe convection, particularly that which deals with the development and maintenance of near-ground vertical vorticity. However, there are a number of unsolved problems with analyzing simulated trajectories that exist near the ground. One of these unsolved problems is how to deal with parcels that pass beneath the lowest scalar model level. Using the CM1 model, which uses a Lorenz grid, the sensitivity of parcel characteristics such as location or potential temperature to the choice of common extrapolation methods is documented. Using potential temperature as an example, it is explained why unphysical tendencies of scalar variables along trajectories may arise once parcels descend beneath the lowest scalar model level. Given the poorly constrained flow (and scalar) fields beneath the lowest scalar model level, errors such as those documented here appear unavoidable when using free-slip boundary conditions.

Original languageEnglish
Pages (from-to)1427-1435
Number of pages9
JournalMonthly Weather Review
Volume146
Issue number5
DOIs
StatePublished - May 1 2018

Keywords

  • Cloud resolving models
  • Subgrid-scale processes
  • Trajectories

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