Upper tropospheric convective outflow in ICON convection-permitting and parameterised set-up

Abstract

<p>The representation of upper tropospheric deep convective divergent outflow (UTDCDO) is compared between ICON-simulations with convection-permitting and convection parameterised set-ups (1 and 13 km resolution) for a convective event over Germany and the Alps on June 10th-11th 2019. Three hypotheses on those UTDCDO have been formulated using idealised Large Eddy Simulations and are now tested on ICON in a convection-permitting set-up: 1. Dimensionality affects the magnitude of UTDCDO in ICON; 2. Convective aggregation and organisation affects the magnitude of those convective outflows in ICON and 3. Convective momentum transport does not affect the magnitude of UTDCDO. A moving box is used to integrate mesoscale divergence, precipitation rate and convective momentum transport. Additionally, ellipse fitting is used to make estimates of convective organisation (dimensionality, area of convective precipitation, etc.).<br />Variability in UTDCDO at a given net latent heating rate is reduced in ICON with parameterised deep convection, compared to the convection-permitting set-up. Hints, but no conclusive results are found on the effect of dimensionality on the magnitude of UT divergent deep convective outflows. An impact of convective organisation and aggregation on UTDCDO is significant in the dataset: as a consequence of outflow collisions, UTDCDO increases sub-linearly with net latent heating. We also found a statistical relation between normalised UTDCDO and normalised convective momentum transport.  </p>

Divergent convective outflow in ICON deep-convection-permitting and parameterised deep convection simulations

“…3.2.1. The workflow as documented here is carried out by scripts published in Groot and Kuntze (2023).…”

“…3). A module named CV2 (as part of OpenCV, 2022, 2024) is used for the ellipse-fitting procedure, and for the technical details, we refer to the code (Groot and Kuntze, 2023). Subsequently, after fitting the ellipses, an initial validation procedure assesses the stability of the ellipse parameters over a 1 h window (next boxes, nos.…”

“…Short-lasting very strong fluctuations are filtered out. Only fluctuations that match any prior and successive record within 1 h are kept (Groot and Kuntze, 2023). The result is a track of each convective system, which may contain one or more gaps of one or several time steps (blue box 6, Fig.…”