סמינר מיוחד בגיאופיזיקה, במדעים אטמוספריים ובמדעי החלל על שם יובל נאמן
Adam Sobel, Columbia University - Sackler Lecturer
ההרצאות המיוחדות בגיאופיזיקה, במדעים אטמוספריים ובמדעי החלל על שם יובל נאמן
נתרמו ע"י ריימונד ובברלי סאקלר
PARAMETERIZATION OF LARGE-SCALE TROPICAL DYNAMICS
Single-column models (SCMs) and limited-area cloud-resolving models (CRMs) have long been used for studies of the interaction of convection with large-scale dynamics. In such models the domain-averaged advection terms cannot be computed just from the model equations, since the large-scale circulation which does the advecting is not explicitly simulated. These terms are typically imposed externally. If they are all set to zero we call the resulting steady solution “radiative-convective equilibrium”. Alternatively, some nonzero advection terms may be imposed, e.g., derived from observations. Whether set to zero or not, these terms - especially the vertical advection terms - exert powerful controls on the model solution. In particular, the vertical advection terms largely control the occurrence and intensity of deep convection, independent of model physics. One cannot use such models to ask why deep convection did or did not occur in any given situation.
In the last decade or so some researchers have experimented with parameterizations of large-scale dynamics. The domain-averaged advection terms are computed from auxiliary equations – truncations of the equations of motion which describe the large-scale dynamics in terms of quantities computed within the model domain. Examples include the weak temperature gradient approximation and the large-scale gravity wave method of Z. Kuang and associates. These methods allow one to use SCMs and limited-domain CRMs to ask why deep convection did or did not occur under specific circumstances, and how deep convection interacts with some types of large-scale disturbances or boundary conditions. There are applications to basic theory and to model development. In this talk I will review these studies, discussing strengths, weaknesses and recent developments.
מארגנת הסמינר: ד"ר רוית חלד