Loading [MathJax]/jax/output/HTML-CSS/fonts/TeX/fontdata.js
Preprints
https://doi.org/10.5194/egusphere-2024-2402
https://doi.org/10.5194/egusphere-2024-2402
23 Aug 2024
 | 23 Aug 2024

The role of ascent timescale for WCB moisture transport into the UTLS

Cornelis Schwenk and Annette Miltenberger

Abstract. Warm conveyor belts (WCBs) are coherent ascending airstreams in extratropical cyclones. They are a major source of moisture for the extratropical upper troposphere and lower stratosphere (UTLS), where moisture acts as a potent greenhouse gas and WCB-associated cirrus contribute to cloud radiative forcing. However, the processes controlling WCB moisture transport and cloud properties are poorly characterised. Furthermore, recent studies have revealed (embedded) convection as a ubiquitous feature of WCBs, highlighting the importance of understanding their updraft and microphysical structure. We present a Lagrangian investigation of WCB moisture transport for a case from the WISE (Wave-driven ISentropic Exchange) campaign based on a convection-permitting simulation. Lagrangian non-dimensional metrics of the moisture budget suggest that the ascent timescale (τ600) strongly controls the end-of-ascent total moisture content, which is largest for slowly ascending trajectories (τ600 > 20 h, ~30 % of all WCB trajectories). This is due to relatively warm end-of-ascent temperatures and the strong temperature control on transported water vapor. Deviations from equilibrium water vapor – condensate partitioning are largest for slow trajectories due to faster glaciation and lower ice crystal numbers. A local moisture transport minimum at intermediate tau600 results from a shift towards a riming dominated precipitation formation pathway and decreasing outflow temperatures with decreasing τ600. The fastest trajectories (τ600 < 5 h, ~5 % of all WCB trajectories) transport the largest condensate mass to the UTLS due to less efficient condensate loss, and produce the longest-lived outflow cirrus. Models that parameterise convection may under-represent these processes, potentially impacting weather forecasts and climate predictions.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Share

Journal article(s) based on this preprint

18 Dec 2024
The role of ascent timescales for warm conveyor belt (WCB) moisture transport into the upper troposphere and lower stratosphere (UTLS)
Cornelis Schwenk and Annette Miltenberger
Atmos. Chem. Phys., 24, 14073–14099, https://doi.org/10.5194/acp-24-14073-2024,https://doi.org/10.5194/acp-24-14073-2024, 2024
Short summary
Download

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
Warm conveyor belts (WCBs) transport moisture into the upper atmosphere, where it acts as a...
Share