Influence of the background wind on the local soil moisture-precipitation feedback

Froidevaux, Paul Arnaud; Schlemmer, Linda; Schmidli, Juerg; Langhans, Wolfgang; Schär, Christoph (2014). Influence of the background wind on the local soil moisture-precipitation feedback. Journal of the atmospheric sciences, 71(2), pp. 782-799. American Meteorological Society 10.1175/JAS-D-13-0180.1

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The importance of soil moisture anomalies on airmass convection over semiarid regions has been recognized in several studies. The underlying mechanisms remain partly unclear. An open question is why wetter soils can result in either an increase or a decrease of precipitation (positive or negative soil moisture–precipitation feedback, respectively). Here an idealized cloud-resolving modeling framework is used to explore the local soil moisture–precipitation feedback. The approach is able to replicate both positive and negative feedback loops, depending on the environmental parameters. The mechanism relies on horizontal soil moisture variations, which may develop and intensify spontaneously. The positive expression of the feedback is associated with the initiation of convection over dry soil patches, but the convective cells then propagate over wet patches where they strengthen and preferentially precipitate. The negative feedback may occur when the wind profile is too weak to support the propagation of convective features from dry to wet areas. Precipitation is then generally weaker and falls preferentially over dry patches. The results highlight the role of the midtropospheric flow in determining the sign of the feedback. A key element of the positive feedback is the exploitation of both low convective inhibition (CIN) over dry patches (for the initiation of convection) and high CAPE over wet patches (for the generation of precipitation).

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Impact
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Froidevaux, Paul Arnaud

Subjects:

500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel

ISSN:

0022-4928

Publisher:

American Meteorological Society

Language:

English

Submitter:

Monika Wälti-Stampfli

Date Deposited:

10 Sep 2014 15:12

Last Modified:

28 Apr 2016 11:40

Publisher DOI:

10.1175/JAS-D-13-0180.1

BORIS DOI:

10.7892/boris.52373

URI:

https://boris.unibe.ch/id/eprint/52373

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