scholarly journals An Evaluation of Eulerian and Semi-Lagrangian Advection Schemes in Simulations of Rotating, Stratified Flows in the Laboratory. Part I: Axisymmetric Flow

2000 ◽  
Vol 128 (8) ◽  
pp. 2835-2852 ◽  
Author(s):  
P. L. Read ◽  
N. P. J. Thomas ◽  
S. H. Risch
Keyword(s):  
Axisymmetric Flow ◽  
Stratified Flows ◽  
Advection Schemes ◽  
Lagrangian Advection ◽  
Rotating Stratified Flows

A Fast Linear Semi-Lagrangian Advection Scheme Coupled with Spectral (bin) Microphysics to Simulate an Idealized Super Cell Storm in WRF

2021 ◽  
Author(s):  
Barry Lynn ◽  
Ehud Gavze ◽  
Jimy Dudhia ◽  
David Gill ◽  
Alexander Khain
Keyword(s):  
Mass Conservation ◽  
Second Order ◽  
Computationally Efficient ◽  
Advection Schemes ◽  
Lagrangian Advection ◽  
Bin Microphysics ◽  
Time Required ◽  
High Level ◽  
Order Components ◽  
Weighting Coefficients

AbstractA new, computationally efficient Semi-Lagrangian advection (SLA) scheme was used to simulate an idealized supercell storm using WRF coupled with Spectral (bin) Microphysics (SBM). SLA was developed to make complicated microphysical schemes more computationally accessible to cloud resolving models. The SLA is a linear combination of Semi-Lagrangian schemes of the first and the second order. It has relatively low numerical diffusion, a high level of mass conservation accuracy, and preserves the sum of multiple advected variables. In addition to idealized tests, comparisons were made with standard WRF higher-order, non-linear advection schemes. Tests of the SLA were performed using different weighting coefficients of γ for the combination of the first and second order components. The results of SLA on grids of 1 km, 500 m, and 250 m agree well with those of the standard WRF advection schemes, with results most similar to simulations with 250 m grid spacing. At the same time, the advection CPU time required by the SLA was 2.2 to 3 times shorter than the WRF advection schemes. The speed-up occurred in part because of the utilization of the same advection matrix for the advection of all hydrometeor mass bins. The findings of this work support the hypothesis that cloud microphysical simulation is more sensitive to the choice of microphysics than to the choice of advection schemes, thereby justifying the use of computationally efficient lower order linear schemes.

scholarly journals Improving the inter-hemispheric gradient of total column atmospheric CO<sub>2</sub> and CH<sub>4</sub> in simulations with the ECMWF semi-Lagrangian atmospheric global model

2016 ◽  
Author(s):  
Anna Agusti-Panareda ◽  
Michail Diamantakis ◽  
Victor Bayona ◽  
Friedrich Klappenbach ◽  
Andre Butz
Keyword(s):  
Climate Models ◽  
Positive Impact ◽  
Computational Cost ◽  
Mass Conservation ◽  
Atmospheric Composition ◽  
Time Range ◽  
Earth System ◽  
Advection Schemes ◽  
Lagrangian Advection ◽  
Total Column

Abstract. It is a widely established fact that standard semi-Lagrangian advection schemes are highly efficient numerical techniques for simulating the transport of atmospheric tracers. However, as they are not formally mass conserving, it is essential to use some method for restoring mass conservation in long time range forecasts. A common approach is to use global mass fixers. This is the case of the semi-Lagrangian advection scheme in the Integrated Forecasting System (IFS) model used by the Copernicus Atmosphere Monitoring Service (CAMS) at the European Centre for Medium range Weather Forecasts (ECMWF). Mass fixers are algorithms with substantial differences in complexity and sophistication but in general of low computational cost. This paper shows the positive impact mass fixers have on the inter-hemispheric gradient of total atmospheric column averaged CO2 and CH4, a crucial feature of their spatial distribution. Two algorithms are compared: the simple "proportional" and the more complex Bermejo &amp; Conde schemes. The former is widely used by several Earth system climate models as well the CAMS global forecasts and analysis of atmospheric composition while the latter has been recently implemented in IFS. Comparisons against total column observations demonstrate that the proportional mass fixer is shown to be suitable for the low resolution simulations but for the high resolution simulations the Bermejo &amp; Conde scheme gives clearly better results. These results have potential repercussions for climate Earth system models using proportional mass fixers as their resolution increases. It also emphasizes the importance of benchmarking the tracer mass fixers with the inter-hemispheric gradient of long-lived greenhouse gases using observations.

scholarly journals The universal aspect ratio of vortices in rotating stratified flows: theory and simulation

2012 ◽  
Vol 706 ◽  
pp. 46-57 ◽  
Author(s):  
Pedram Hassanzadeh ◽  
Philip S. Marcus ◽  
Patrice Le Gal
Keyword(s):  
Aspect Ratio ◽  
Three Dimensional ◽  
Boussinesq Equations ◽  
Stratified Flows ◽  
Coriolis Parameter ◽  
Aspect Ratios ◽  
Ideal Gases ◽  
Horizontal Length ◽  
Background Density ◽  
Rotating Stratified Flows

AbstractWe derive a relationship for the vortex aspect ratio $\ensuremath{\alpha} $ (vertical half-thickness over horizontal length scale) for steady and slowly evolving vortices in rotating stratified fluids, as a function of the Brunt–Väisälä frequencies within the vortex ${N}_{c} $ and in the background fluid outside the vortex $\bar {N} $, the Coriolis parameter $f$ and the Rossby number $\mathit{Ro}$ of the vortex: ${\ensuremath{\alpha} }^{2} = \mathit{Ro}(1+ \mathit{Ro}){f}^{2} / ({ N}_{c}^{2} \ensuremath{-} {\bar {N} }^{2} )$. This relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and the background density gradient need not be uniform. Our relation for $\ensuremath{\alpha} $ has many consequences for equilibrium vortices in rotating stratified flows. For example, cyclones must have ${ N}_{c}^{2} \gt {\bar {N} }^{2} $; weak anticyclones (with $\vert \mathit{Ro}\vert \lt 1$) must have ${ N}_{c}^{2} \lt {\bar {N} }^{2} $; and strong anticyclones must have ${ N}_{c}^{2} \gt {\bar {N} }^{2} $. We verify our relation for $\ensuremath{\alpha} $ with numerical simulations of the three-dimensional Boussinesq equations for a wide variety of vortices, including: vortices that are initially in (dissipationless) equilibrium and then evolve due to an imposed weak viscous dissipation or density radiation; anticyclones created by the geostrophic adjustment of a patch of locally mixed density; cyclones created by fluid suction from a small localized region; vortices created from the remnants of the violent breakups of columnar vortices; and weakly non-axisymmetric vortices. The values of the aspect ratios of our numerically computed vortices validate our relationship for $\ensuremath{\alpha} $, and generally they differ significantly from the values obtained from the much-cited conjecture that $\ensuremath{\alpha} = f/ \bar {N} $ in quasi-geostrophic vortices.

Sign in / Sign up

Export Citation Format

Share Document