A multidecadal simulation of Atlantic tropical cyclones using a variable-resolution global atmospheric general circulation model

Colin M. Zarzycki, Christiane Jablonowski

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Using a variable-resolution option within the National Center for Atmospheric Research/Department of Energy Community Atmosphere Model (CAM) Spectral Element (SE) global model, a refined nest at 0.25° (28 km) horizontal resolution located over the North Atlantic is embedded within a global 1° (111 km) grid. The grid is designed such that fine grid cells are located where tropical cyclones (TCs) are observed to occur during the Atlantic TC season (June-November). Two simulations are compared, one with refinement and one control case with no refinement (globally uniform 1° grid). Both simulations are integrated for 23 years using Atmospheric Model Intercomparison Protocols. TCs are tracked using an objective detection algorithm. The variable-resolution simulation produces significantly more TCs than the unrefined simulation. Storms that do form in the refined nest are much more intense, with multiple storms strengthening to Saffir-Simpson category 3 intensity or higher. Both count and spatial distribution of TC genesis and tracks in the variable-resolution simulation are well matched to observations and represent significant improvements over the unrefined simulation. Some degree of interannual skill is noted, with the variable-resolution grid able to reproduce the observed connection between Atlantic TCs and the El Niño-Southern Oscillation (ENSO). It is shown that Genesis Potential Index (GPI) is well matched between the refined and unrefined simulations, implying that the introduction of variable-resolution does not affect the synoptic environment. Potential "upscale" effects are noted in the variable-resolution simulation, suggesting stronger TCs in refined nests may play a role in meridional transport of momentum, heat, and moisture.

Original languageEnglish (US)
Pages (from-to)805-828
Number of pages24
JournalJournal of Advances in Modeling Earth Systems
Issue number3
StatePublished - Aug 21 2015


All Science Journal Classification (ASJC) codes

  • Global and Planetary Change
  • Environmental Chemistry
  • Earth and Planetary Sciences(all)

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