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Super-Clausius-Clapeyron scaling of extreme hourly convective precipitation and its relation to large-scale atmospheric conditions

Lookup NU author(s): Dr Renaud Barbero, Professor Hayley Fowler

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Abstract

© 2017 American Meteorological Society. Present-day precipitation-temperature scaling relations indicate that hourly precipitation extremes may have a response to warming exceeding the Clausius-Clapeyron (CC) relation; for the Netherlands the dependency on surface dewpoint temperature follows 2 times the CC relation (2CC). The authors' hypothesis- as supported by a simple physical argument presented here-is that this 2CC behavior arises from the physics of convective clouds. To further investigate this, the large-scale atmospheric conditions accompanying summertime afternoon precipitation events are analyzed using surface observations combined with a regional reanalysis. Events are precipitation measurements clustered in time and space. The hourly peak intensities of these events again reveal a 2CC scaling with the surface dewpoint temperature. The temperature excess of moist updrafts initialized at the surface and the maximumcloud depth are clear functions of surface dewpoint, confirming the key role of surface humidity on convective activity. Almost no differences in relative humidity and the dry temperature lapse rate were found across the dewpoint temperature range, supporting the theory that 2CC scaling is mainly due to the response of convection to increases in near-surface humidity, while other atmospheric conditions remain similar. Additionally, hourly precipitation extremes are on average accompanied by substantial large-scale upward motions and therefore large-scale moisture convergence, which appears to accelerate with surface dewpoint. Consequently, most hourly extremes occur in precipitation events with considerable spatial extent. Importantly, this event size appears to increase rapidly at the highest dewpoint temperature range, suggesting potentially strong impacts of climatic warming.


Publication metadata

Author(s): Lenderink G, Barbero R, Loriaux JM, Fowler HJ

Publication type: Article

Publication status: Published

Journal: Journal of Climate

Year: 2017

Volume: 30

Issue: 15

Pages: 6037-6052

Print publication date: 01/08/2017

Online publication date: 10/05/2017

Acceptance date: 14/03/2017

ISSN (print): 0894-8755

ISSN (electronic): 1520-0442

Publisher: American Meteorological Society

URL: https://doi.org/10.1175/JCLI-D-16-0808.1

DOI: 10.1175/JCLI-D-16-0808.1


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