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Dry soils can intensify mesoscale convective systems

Klein, Cornelia ORCID: https://orcid.org/0000-0001-6686-0458; Taylor, Christopher M. ORCID: https://orcid.org/0000-0002-0120-3198. 2020 Dry soils can intensify mesoscale convective systems. Proceedings of the National Academy of Sciences, 117 (35). 21132-21137. https://doi.org/10.1073/pnas.2007998117

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Abstract/Summary

Soil moisture can feed back on rainfall through the impact of surface fluxes on the environment in which convection develops. The vast majority of previous research has focused on the initiation of convection, but in many regions of the world, the majority of rain comes from remotely triggered mesoscale convective systems (MCSs). Here we conduct a systematic observational analysis of soil moisture feedbacks on propagating MCSs anywhere in the world and show a strong positive impact of drier soils on convection within mature MCSs. From thousands of storms captured in satellite imagery over the Sahel, we find that convective cores within MCSs are favored on the downstream side of dry patches ≥200 km across. The effect is particularly strong during the afternoon–evening transition when convection reaches its diurnal peak in intensity and frequency, with dry soils accounting for an additional one in five convective cores. Dry soil patterns intensify MCSs through a combination of convergence, increased instability, and wind shear, all factors that strengthen organized convection. These favorable conditions tend to occur in the vicinity of a surface-induced anomalous displacement of the Sahelian dry line/intertropical discontinuity, suggesting a strong link between dry line dynamics and soil moisture state. Our results have important implications for nowcasting of severe weather in the Sahel and potentially in other MCS hotspot regions of the world.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1073/pnas.2007998117
UKCEH and CEH Sections/Science Areas: Hydro-climate Risks (Science Area 2017-)
ISSN: 0027-8424
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - full text available via Official URL link.
Additional Keywords: mesoscale convective systems, propagating convection, soil moisture, dry line
NORA Subject Terms: Agriculture and Soil Science
Date made live: 15 Sep 2020 10:39 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/528477

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