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A minor modification of the gnomonic cubed-shaped sphere grid that offers advantages in the context of implementing moving hurricane nests
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2017
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Description:The next generation of operational weather and climate prediction models of the National Weather Service is planned to comprise versions of the GFDL FiniteVolume Cubed-Sphere Dynamical Core (FV3). In order to address the need to accommodate storm-tracking movable nests during seasons when tropical storms are active, we will be confronted with cases where the nested grid must pass over the corners of the cubed sphere grid, which are situated at approximately 35° of latitude. Although this latitude is already sufficiently large to make such a passage relatively rare, and although there is no doubt that the technical challenge of achieving a smoothly-progressing nest in such a situation will be (indeed, must be) met, a very small modification to the parent grid, from purely cubic to prolate prismatic, might be an attractive way to make these occurrences even less frequent. This note presents what seems to be an elegant way that such a minor modification of the grid might be made without changing two of its characteristic features: the grid lines will all remain great circles on the sphere; and the grid cells at the centers of each of the six 'tiles' will remain square. The equiangular distribution of those of the grid lines of the equator-straddling tiles that correspond to lines of constant longitude is also preserved (the other families of grid line s are no longer perfectly uniformly spaced in angle). But by nudging the latitudes of the tile corners poleward by even a very small angle we will fairly dramatically further reduce the frequency at which storm-tracking nests will need to interact with these corners of the parent grid. [doi:10.7289/V5/ON-NCEP-486: (https://doi:10.7289/V5/ON-NCEP-486)]
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Content Notes:R. James Purser and Mingjing Tong.
"June 13, 2017."
"This is an unreviewed manuscript, primarily intended for informal exchange of information among NMC staff members."
System requirements: Adobe Acrobat Reader.
Includes bibliographical references (pages 10-11).
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Rights Information:Public Domain
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