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Title: Impact of topography on the diurnal cycle of summertime moist convection in idealized simulations

The impact of an isolated mesoscale mountain on the diurnal cycle of moist convection and its spatial variation is investigated. Convection-resolving simulations of flow over 3D Gaussian-shaped mountains are performed for a conditionally unstable atmosphere under diurnal radiative forcing. The results show considerable spatial variability in terms of timing and amount of convective precipitation. This variability relates to different physical mechanisms responsible for convection initiation in different parts of the domain. During the late morning, the mass convergence from the radiatively driven diurnal upslope flow confronting the large-scale incident background flow triggers strong convective precipitation over the mountain lee slope. As a consequence, instabilities in the boundary layer are swept out by the emerging cold pool in the vicinity of the mountain, and some parts over the mountain near-field receive less rainfall than the far-field. Over the latter, an unperturbed boundary-layer growth allows for sporadic convective initiation. Still, secondary convection triggered over the leading edge of the cold pool spreads some precipitation over the downstream near-field. Detailed analysis of our control simulation provides further explanation of this frequently observed precipitation pattern over mountains and adjacent plains. Sensitivity experiments indicate a significant influence of the mountain height on the precipitation patternmore » over the domain.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1]
  1. Swiss Federal Inst. of Technology (ETH), Zurich (Switzerland). Inst. for Atmospheric and Climate Science
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division
Publication Date:
Grant/Contract Number:
AC02-05CH11231; 200021-132614
Type:
Accepted Manuscript
Journal Name:
Meteorologische Zeitschrift (Berlin)
Additional Journal Information:
Journal Name: Meteorologische Zeitschrift (Berlin); Journal Volume: 25; Journal Issue: 2; Journal ID: ISSN 0941-2948
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE; Swiss National Science Foundation (SNSF)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; moist convection; precipitation; diurnal cycle; topography; idealized studies; summertime
OSTI Identifier:
1378730

Hassanzadeh, Hanieh, Schmidli, Jürg, Langhans, Wolfgang, Schlemmer, Linda, and Schär, Christoph. Impact of topography on the diurnal cycle of summertime moist convection in idealized simulations. United States: N. p., Web. doi:10.1127/metz/2015/0653.
Hassanzadeh, Hanieh, Schmidli, Jürg, Langhans, Wolfgang, Schlemmer, Linda, & Schär, Christoph. Impact of topography on the diurnal cycle of summertime moist convection in idealized simulations. United States. doi:10.1127/metz/2015/0653.
Hassanzadeh, Hanieh, Schmidli, Jürg, Langhans, Wolfgang, Schlemmer, Linda, and Schär, Christoph. 2015. "Impact of topography on the diurnal cycle of summertime moist convection in idealized simulations". United States. doi:10.1127/metz/2015/0653. https://www.osti.gov/servlets/purl/1378730.
@article{osti_1378730,
title = {Impact of topography on the diurnal cycle of summertime moist convection in idealized simulations},
author = {Hassanzadeh, Hanieh and Schmidli, Jürg and Langhans, Wolfgang and Schlemmer, Linda and Schär, Christoph},
abstractNote = {The impact of an isolated mesoscale mountain on the diurnal cycle of moist convection and its spatial variation is investigated. Convection-resolving simulations of flow over 3D Gaussian-shaped mountains are performed for a conditionally unstable atmosphere under diurnal radiative forcing. The results show considerable spatial variability in terms of timing and amount of convective precipitation. This variability relates to different physical mechanisms responsible for convection initiation in different parts of the domain. During the late morning, the mass convergence from the radiatively driven diurnal upslope flow confronting the large-scale incident background flow triggers strong convective precipitation over the mountain lee slope. As a consequence, instabilities in the boundary layer are swept out by the emerging cold pool in the vicinity of the mountain, and some parts over the mountain near-field receive less rainfall than the far-field. Over the latter, an unperturbed boundary-layer growth allows for sporadic convective initiation. Still, secondary convection triggered over the leading edge of the cold pool spreads some precipitation over the downstream near-field. Detailed analysis of our control simulation provides further explanation of this frequently observed precipitation pattern over mountains and adjacent plains. Sensitivity experiments indicate a significant influence of the mountain height on the precipitation pattern over the domain.},
doi = {10.1127/metz/2015/0653},
journal = {Meteorologische Zeitschrift (Berlin)},
number = 2,
volume = 25,
place = {United States},
year = {2015},
month = {8}
}