Abstract Recent observational and numerical studies have investigated the dynamics of fine‐scale gravity waves radiating horizontally outward from tropical cyclones. The waves are wrapped into spirals by the tangential wind of the cyclone and are described as spiral gravity waves. This study addresses how well numerical simulations of these waves compare to observations as the horizontal grid spacing is decreased from 2.0 to 1.0 to 0.5 km, and the number of vertical levels changes from 25 to 50 to 100. Spectral filtering is applied to separate the fine‐scale waves in vertical velocity (w) and the larger‐scale waves in pressure (p) from moist updrafts and downdrafts in the eyewall and rainbands. As the grid spacing decreases, the radial wavelengths of thewwaves decrease from 20 to 7 km, approaching observed values. For grid spacing 1.0 km, thepwaves become well‐resolved with wavelength 70 km. The outward phase speeds range from 15 to 30 ms−1for thewwaves and 50 to 70 ms−1forpwaves. Analysis of the upper‐level outflow region finds that the spiralwwaves propagate 5–10 ms−1faster due to radial advection, but also finds what appear to be different classes of larger‐amplitude, slow‐moving spiral waves. Similar waves can be seen in satellite images, which appear to be caused by dynamical instability of the strongly vertically sheared radial and tangential winds in the TC outflow.
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DCMIP2016: the tropical cyclone test case
Abstract. This paper describes and analyzes the Reed–Jablonowski (RJ) tropical cyclone (TC) test case used in the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016). This intermediate-complexity test case analyzes the evolution of a weak vortex into a TC in an idealized tropical environment. Reference solutions from nine general circulation models (GCMs) with identical simplified physics parameterization packages that participated in DCMIP2016 are analyzed in this study at 50 km horizontal grid spacing, with five of these models also providing solutions at 25 km grid spacing. Evolution of minimum surface pressure (MSP) and maximum 1 km azimuthally averaged wind speed (MWS), the wind–pressure relationship, radial profiles of wind speed and surface pressure, and wind composites are presented for all participating GCMs at both horizontal grid spacings. While all TCs undergo a similar evolution process, some reach significantly higher intensities than others, ultimately impacting their horizontal and vertical structures. TCs simulated at 25 km grid spacings retain these differences but reach higher intensities and are more compact than their 50 km counterparts. These results indicate that dynamical core choice is an essential factor in GCM development, and future work should be conducted to explore how specific differences within the dynamical core affect TC behavior in GCMs.
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- Award ID(s):
- 2005137
- PAR ID:
- 10616548
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- European Geosciences Union
- Date Published:
- Journal Name:
- Geoscientific Model Development
- Volume:
- 17
- Issue:
- 7
- ISSN:
- 1991-9603
- Page Range / eLocation ID:
- 2493 to 2507
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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