Impacts of Deep and Shallow Convection on the Gross Moist Stability

This paper presents a method for extracting deep and shallow convection modes from the total vertical velocity field that can be used to perform different effects on tropical climate. Based on the empirical orthogonal function (EOF) and principal component analysis (PCA), we separate the vertical velocity into two typical modes: the top-heavy mode associated with deep convection and the bottom-heavy mode associated with shallow convection. Accordingly, we calculate the corresponding gross moist stability (GMS) for these two modes and discuss their impacts on tropical climate. The GMS of deep convection is generally positive, while that of shallow convection tends to be negative. This implies that deep convection acts to stabilize the atmosphere while shallow convection inclines to destabilize the atmosphere. A further analysis of the thermodynamic profile shows that differences in moisture profile attribute to the above contrast between deep and shallow convection. This result provides a more realistic way to examine the atmospheric stability.