Novel three-pattern decomposition of global atmospheric circulation: generalization of traditional two-dimensional decomposition

Abstract

This study investigates the differences and connections between the three-pattern decomposition of global atmospheric circulation, the representation of the horizontal vortex circulation in the middle–high latitudes and the local partitioning of the overturning circulation in the tropics. It concludes that the latter two methods are based on the traditional two-dimensional (2D) decomposition of the vortex and divergent circulations in the fluid dynamics and that the three-pattern decomposition model is not a simple superposition of the two traditional methods but a new three-dimensional (3D) decomposition of global atmospheric circulation. The three-pattern decomposition model can decompose the vertical vorticity of atmosphere into three parts: one part is caused by the horizontal circulation, whereas the other two parts are induced by divergent motions, which correspond to the zonal and meridional circulations. The diagnostic results from the decomposed vertical vorticities accord well with the classic theory: the atmospheric motion at 500 hPa is quasi-horizontal and nondivergent and can represent the vertical mean state of the entire atmosphere. The analysis of the climate characteristics shows that the vertical vorticities of the zonal and meridional circulations are the main cause of the differences between the three-pattern circulations and traditional circulations. The decomposition of the vertical vorticity by the three-pattern decomposition model offers new opportunities to quantitatively study the interaction mechanisms of the Rossby, Hadley and Walker circulations using the vorticity equation.