Dynamic and Thermodynamic Environmental Modulation of Tropical Congestus and Cumulonimbus in Maritime Tropical Regions

We have quantified the impacts of varying thermodynamic environments on tropical15 congestus and cumulonimbus clouds (CCCs) within maritime tropical regions. To elucidate16 this relationship, we employed the Regional Atmospheric Modeling System (RAMS) to17 conduct high-resolution (1km) simulations of convection over the Philippine Archipelago for18 a month-long period in 2019. We subsequently performed a cloud-object-based analysis,19 identifying and tracking hundreds of thousands of individual CCCs using the Tracking and20 Object-Based Analysis of Clouds (tobac) tracking library. Using this object-oriented dataset21 of tracked cells, we examined differences in individual storm strength, organization, and22 morphology due to the storm’s initial environment. We found that storm strength, defined23 here as maximum midlevel updraft velocity, was controlled primarily by ConvectiveAvailable Potential Energy (CAPE) and Precipitable Water (PW); high CAPE (>2500 J kg-1 24 )25 and high (approximately 63 mm) PW were both required for midlevel CCC updraft velocitiesto reach at least 10 m s-1 26 . Of the CCCs with the most vigorous updrafts, 80.9% were also in27 the upper tercile of precipitation rates, with the strongest precipitation rates requiring even28 higher PW. Further, we found that vertical wind shear was the primary differentiator between29 organized and isolated convective storms. Within the set of organized storms, linearly30 oriented CCC systems have significantly weaker vertical wind shear than nonlinear CCCs in31 low- (0-1 km, 0-3 km) and mid-levels (0-5 km, 2-7 km). Overall, these results provide new32 insights into the environmental conditions determining the CCC properties in maritime33 tropical regions.