Parallel Semi-Lagrangian Advection using PVM

Abstract. The dispersion of volcanic emissions in the Earth atmosphere is of interest for climate research, air traffic control and human wellbeing. Current volcanic emission dispersion models rely on fixed-grid structures that often are not able to resolve the fine filamented structure of volcanic emissions being transported in the atmosphere. Here we extend an existing adaptive semi-Lagrangian advection model for volcanic emissions including the sedimentation of volcanic ash. The advection of volcanic emissions is driven by a precalculated wind field. For evaluation of the model, the explosive eruption of Mount Pinatubo in June 1991 is chosen, which was one of the largest eruptions in the 20th century. We compare our simulations of the climactic eruption on 15 June 1991 to satellite data of the Pinatubo ash cloud and evaluate different sets of input parameters. We could reproduce the general advection of the Pinatubo ash cloud and, owing to the adaptive mesh, simulations could be performed at a high local resolution while minimizing computational cost. Differences to the observed ash cloud are attributed to uncertainties in the input parameters and the course of Typhoon Yunya, which is probably not completely resolved in the wind data used to drive the model. The best results were achieved for simulations with multiple ash particle sizes.

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A Fully Lagrangian Advection Scheme

Journal of Scientific Computing ◽

10.1007/s10915-014-9928-8 ◽

2014 ◽

Vol 64 (1) ◽

pp. 151-177 ◽

Cited By ~ 2

Author(s):

John C. Bowman ◽

Mohammad Ali Yassaei ◽

Anup Basu

Keyword(s):

Advection Scheme ◽

Lagrangian Advection

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Forward Semi-Lagrangian Advection with Mass Conservation and Positive Definiteness for Falling Hydrometeors

Monthly Weather Review ◽

10.1175/2009mwr3109.1 ◽

2010 ◽

Vol 138 (5) ◽

pp. 1778-1791 ◽

Cited By ~ 11

Author(s):

Hann-Ming Henry Juang ◽

Song-You Hong

Keyword(s):

Linear Method ◽

Mass Conservation ◽

Terminal Velocity ◽

Cloud Microphysics ◽

Squall Line ◽

Test Bed ◽

Time Step ◽

Microphysics Scheme ◽

Advection Scheme ◽

Lagrangian Advection

Abstract A semi-Lagrangian advection scheme is developed for falling hydrometeors in hopes of replacing the conventional Eulerian scheme that has been widely used in the cloud microphysics scheme of numerical atmospheric models. This semi-Lagrangian scheme uses a forward advection method to determine the advection path with or without iteration, and advected mass in a two-time-level algorithm with mass conservation. Monotonicity is considered in mass-conserving interpolation between Lagrangian grids and model Eulerian grids, thus making it a positive definite advection scheme. For mass-conserving interpolation between the two grid systems, the piecewise constant method (PCM), piecewise linear method (PLM), and piecewise parabolic method (PPM) are proposed. The falling velocity at the bottom cell edge is modified to avoid unphysical deformation by scanning from the top layer to the bottom of the model, which enables the use of a large time step with reasonable accuracy. The scheme is implemented and tested in the Weather Research and Forecasting (WRF) Single-Moment 3-Class Microphysics Scheme (WSM3). In a theoretical test bed with constant terminal velocity, the proposed semi-Lagrangian algorithm shows that the higher-order interpolation scheme produces less diffusive features at maximal precipitation. Results from another idealized test bed with mass-weighted terminal velocity demonstrate that the accuracy of the proposed scheme is still satisfactory even with a time step of 120 s when the mean terminal velocity averaged at the departure and arrival points is employed. A two-dimensional (2D) squall-line test using the WSM3 scheme shows that the control run with the Eulerian advection scheme and the semi-Lagrangian run with the PCM method reveal similar results, whereas behaviors using the PLM and PPM are similar with higher-resolution features, such as mammatus-like clouds.

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A Semi-Lagrangian Advection Scheme with Modified Exponential Splines

Monthly Weather Review ◽

10.1175/1520-0493(1996)124<0716:aslasw>2.0.co;2 ◽

1996 ◽

Vol 124 (4) ◽

pp. 716-729 ◽

Cited By ~ 3

Author(s):

Michael Böttcher

Keyword(s):

Advection Scheme ◽

Lagrangian Advection

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Semi-Lagrangian Advection of Stratospheric Ozone on a Yin–Yang Grid System

Monthly Weather Review ◽

10.1175/mwr-d-15-0142.1 ◽

2016 ◽

Vol 144 (3) ◽

pp. 1035-1050 ◽

Cited By ~ 9

Author(s):

Jean de Grandpré ◽

Monique Tanguay ◽

Abdessamad Qaddouri ◽

Mohamed Zerroukat ◽

Chris A. McLinden

Keyword(s):

Chemical Constituents ◽

Stratospheric Ozone ◽

Weather Prediction ◽

Mass Conservation ◽

Spatiotemporal Variability ◽

Grid System ◽

Shape Preserving ◽

Conservation Property ◽

Yin Yang ◽

Lagrangian Advection

Abstract The lack of formal mass conservation that is inherent to the standard semi-Lagrangian transport scheme represents a significant model limitation that needs to be addressed. The magnitude of this impact depends on the nature of the advected quantity and particularly on the strength of species spatiotemporal variability. In this study, this issue is examined in the context of two configurations of the Environment Canada Global Environmental Multiscale (GEM) model. The first configuration (GEM Lat–Lon) is based on a global latitude–longitude grid system with the Arakawa C grid in the horizontal. The second configuration (GEM Yin–Yang) uses the overset Yin–Yang grid, which is singularity free and has quasi-uniform resolution. Both model versions have been used for studying the mass conservation property of passive and nonpassive tracers such as stratospheric ozone using different shape-preserving schemes and a global mass fixer. Experiments with idealized tracers indicate that the implementation of a global mass fixer and a conservative shape-preserving scheme reduces the error field in both 2D and 3D configurations. In the case of stratospheric ozone, the study demonstrates that the mass conservation error is significantly reduced with the use of the Yin–Yang grid. This is attributed to the quasi-uniform nature of the grid that contributes to improve the accuracy of the computation particularly in high-latitude regions where most of the ozone mass resides. The study demonstrates the potential benefits of using a quasi-uniform Yin–Yang grid system and shows that chemical constituents can serve as a useful diagnostic for the evaluation of numerical weather prediction (NWP) models.

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