Giga-LES of Hector the Convector and Its Two Tallest Updrafts up to the Stratosphere

Abstract

The dynamics of Hector the Convector, which overshot into the stratosphere on 30 November 2005 over the Tiwi Islands, Australia, is investigated using a giga-large-eddy simulation with a 100-m cubic mesh. Individual updrafts, defined as 3D objects with vertical velocity above 10 m s−1 are identified. Among the 20 000 updrafts formed during the most intense phase, only a dozen were more than 4 km tall. The two tallest updrafts accounted for more than 90% of the total vertical mass flux through the tropical tropopause layer. Their locations were determined by low-level convergence lines first created by the sea breeze in the morning, then enhanced by cold pools due to cumulus congestus. They finally reinforced each other as they moved inland and intersected. The two tallest updrafts that overshot the tropopause were contrasted with those occurring 1 h earlier and later. They presented larger widths (up to 8 km), greater buoyancy (up to 0.1 m s−2), stronger vertical velocities (up to 50 m s−1), and larger hydrometeor contents (more than 10 g kg−1). They kept their core weakly diluted on their way to the stratosphere with an entrainment rate as low as 0.08 km−1. Both the low-level convergence lines intensified by cold pools and the reduced mixing in the troposphere were found to be the determinant for the transition from deep to very deep convection.

Examining relationships between cloud‐resolving model parameters and total flash rates to generate lightning density maps

“…Thus, their involvement in the charge generation and the lightning activity is different: cells that are not, or only slightly, electrified are included in the analysis and could bias the relationships. Another reason leading to cell‐scale analysis is the growing interest of convection‐permitting simulations over large domains (Pantillon et al ; Fierro et al ; Dauhut et al , among others). In such cases or in NWP model configurations, estimating the lightning activity based on relationships computed for the overall domain can be misleading.…”

Overview of the Meso-NH model version 5.4 and its applications

“…This technique was developed by Dauhut et al (2016) to identify the few 15 updrafts of Hector the Convector in the Northern Territories of Australia from among the more than 16,000 updrafts that hydrate the stratosphere. Updrafts were defined as three-dimensional objects made of connected grid points for which the vertical velocity exceeded an arbitrary threshold.…”

Assessing Convective Organization in Tropical Radar Observations

“…A higher degree of deep convective organization is often associated with the term "cluster" (e.g., Leary & Houze, 1979;Hohenegger & Stevens, 2016;Weger et al, 1992), indicating that several convective objects exist in close proximity or form coherent structures. Clustering of convection can occur through processes internal to the convection, such as cold pools (e.g., Haerter et al, 2019) and radiative feedbacks (e.g., Coppin & Bony, 2015), or they can be external, such as land-sea-breezes (e.g., Dauhut et al, 2016) or wind shear (e.g., Rotunno et al, 1988). Many of the clustering mechanisms result in spatially extensive convective systems.…”