Preprints
https://doi.org/10.5194/egusphere-2025-1637
https://doi.org/10.5194/egusphere-2025-1637
17 Apr 2025
 | 17 Apr 2025

Unexpected characteristics of convective downdrafts in the upper-levels of tropical deep convective clouds

Sreehari Kizhuveettil, Jordi Vila-Guerau de Arellano, Martina Krämer, Armin Afchine, Luiz A. T. Machado, Martin Zöger, and Wiebke Frey

Abstract. This study investigates the thermodynamical and microphysical links of in-cloud downdrafts of tropical deep convective clouds using aircraft measurements from ACRIDICON-CHUVA field campaign focusing on the upper-levels (10–14 km). The Cloud Water Content (CWC) does not show a discernible trend with altitude or vertical velocity. This opposes the concept of condensate loading, enhancing the downdraft strength. Furthermore, the CWC in up- and downdrafts is found to be similar. The mean draft diameters exhibit a broadening trend with altitude in updrafts and downdrafts, while the mean air mass flux decreases with altitude. In the upper-levels, strong negative vertical velocities (w < -2 m s-1) are observed in the supersaturated region (RHice > 110 %), contradicting the general idea that downdrafts are driven/maintained by latent cooling. The spread in cloud particle number concentration was found to be similar in downdraft and updraft regions with a weak linear trend for |w| > 1 m s-1 in transition (90 ≤ RHice ≤ 110 %) and supersaturated regions. The mean particle size distributions (PSDs) indicate an increase in maximum particle size with altitude. Higher particle concentrations are observed in stronger drafts for particles with Dp< 100 m. Furthermore, the number concentration of larger particles (Dp > 100 m) increases faster in stronger drafts as altitude increases. Particle number concentrations in downdrafts are comparable to those in updrafts of similar strength at the same altitude. We speculate that large eddies that allow mixing between updrafts and downdrafts have an influence on the modulation of PSDs.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.

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Sreehari Kizhuveettil, Jordi Vila-Guerau de Arellano, Martina Krämer, Armin Afchine, Luiz A. T. Machado, Martin Zöger, and Wiebke Frey

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Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1637', Anonymous Referee #1, 11 May 2025
  • RC2: 'Comment on egusphere-2025-1637', Anonymous Referee #2, 16 Jun 2025
  • EC1: 'Editor comment on egusphere-2025-1637', Raphaela Vogel, 25 Jun 2025
Sreehari Kizhuveettil, Jordi Vila-Guerau de Arellano, Martina Krämer, Armin Afchine, Luiz A. T. Machado, Martin Zöger, and Wiebke Frey
Sreehari Kizhuveettil, Jordi Vila-Guerau de Arellano, Martina Krämer, Armin Afchine, Luiz A. T. Machado, Martin Zöger, and Wiebke Frey

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Short summary
Aircraft measurements are used to investigate high-altitude downdrafts in tropical deep convective clouds. The cloud water present in the downdrafts and its intensity do not show any correlation. Surprisingly, downdrafts occurred in supersaturated regions, contradicting the classical view of subsaturated downdrafts. Up- and downdrafts of similar strength show similar particle size distributions. These findings shed new light on the interplay between deep convection dynamics and microphysics.
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