Dependence of model energy spectra on vertical resolution
Waite, Michael L
MetadataShow full item record
Many high-resolution atmospheric models can reproduce the qualitative shape of the atmospheric kinetic energy spectrum, which has a power-law slope of −3 at large horizontal scales that shallows to approximately −5/3 in the mesoscale. This paper investigates the possible dependence of model energy spectra on the vertical grid resolution. Idealized simulations forced by relaxation to a baroclinically unstable jet are performed for a wide range of vertical grid spacings Δz. Energy spectra are converged for Δz 200 m but are very sensitive to resolution with 500 m ≤ Δz ≤ 2 km. The nature of this sensitivity depends on the vertical mixing scheme. With no vertical mixing or with weak, stability-dependent mixing, the mesoscale spectra are artificially amplified by low resolution: they are shallower and extend to larger scales than in the converged simulations. By contrast, vertical hyperviscosity with fixed grid-scale damping rate has the opposite effect: underresolved spectra are spuriously steepened. High-resolution spectra are converged except for the stability-dependent mixing case, which are damped by excessive mixing due to enhanced shear over a wide range of horizontal scales. It is shown that converged spectra require resolution of all vertical scales associated with the resolved horizontal structures: these include quasigeostrophic scales for large-scale motions with small Rossby number and the buoyancy scale for small-scale motions at large Rossby number. It is speculated that some model energy spectra may be contaminated by low vertical resolution, and it is recommended that vertical-resolution sensitivity tests always be performed.
Cite this work
Michael L Waite (2016). Dependence of model energy spectra on vertical resolution. UWSpace. http://hdl.handle.net/10012/10538
Showing items related by title, author, creator and subject.
Calibration of Hydrologic Models Using Distributed Surrogate Model Optimization Techniques: A WATCLASS Case Study Kamali, Mahtab (University of Waterloo, 2009-02-20)This thesis presents a new approach to calibration of hydrologic models using distributed computing framework. Distributed hydrologic models are known to be very computationally intensive and difficult to calibrate. To ...
Visakhamoorthy, Sona (University of Waterloo, 2011-08-30)With growing concerns over emissions, homogeneous charge compression ignition (HCCI) engines offer a promising solution through reducing NOx and particulate emissions and increasing efficiency. However, this technology is ...
Lai, Xiaoni (University of Waterloo, 2015-06-04)A model of the feature-oriented requirements of a software system usually contains a large number of non-trivial features; each feature may have unintended interactions with other features. It may be difficult to comprehend ...