Objective convective updraft identification and tracking: Part 1. Structure and thermodynamics of convection in the rainband regions of two hurricane simulations

To better understand the life cycles of convective elements in numerical model simulations, a convective updraft tracking algorithm, dubbed the Statistical and Programmable Objective Updraft Tracker (SPOUT), is developed. SPOUT identifies updraft cores in horizontal slices through a given model data set, links these cores in three dimensions to form vertically coherent updrafts, and then tracks updrafts in time via estimates of the mean local advection. SPOUT is evaluated in idealized hurricane simulations from both the Regional Atmospheric Modeling System (RAMS) and Weather Research and Forecasting (WRF). In both simulations, SPOUT indicates most updrafts live less than 60 min, but some can persist for over 2 h. Updrafts are typically manifested as shallow cumulus, cumulus congestus, and deep cumulonimbus. Overall, there is reasonable agreement between the vigor of convection and the amount of localized conditional convective instability. Also, the majority of updrafts attain a tilted structure that is in accordance with the localized vertical wind shear. Nonetheless, there are striking differences between models, with the higher-resolution WRF simulation producing around twice as many updrafts as RAMS. Moreover, the WRF updrafts are significantly weaker. This paper highlights the utility of SPOUT for studying convective life cycles in high-resolution numerical simulations and provides some basic features of convection in two hurricane simulations.