The unique behavior of vertical velocity in developing deep convection

When daytime tropical convection develops away from mesoscale disturbances, it typicallytransitions gradually from dry to shallow to deep convection on hourly timescales.The transition is commonly associated with the formation of larger horizontalboundary-layer structures and an increasing level of cloud organization aloft.This study demonstrates that a spectral analysis of the resolved high-resolutionsub-cloud flow features allows for a robust identificationof dominant length scales and the quantification of their growth rates during the transition.Furthermore, it is shown that temperature, moisture, and horizontal winds develop multiple length scales with the largest ones growing up to several kilometers.However, the vertical velocity's length scale behaves in a significantly distinct manner and saturates at much lower values, comparable over land and ocean.This indicates stronger inherent limits of vertical velocity to self-organize beyondcertain scales, at least for surface-driven developing deep convection.