TY - JOUR

T1 - Large-eddy simulation of catchment-scale circulation

AU - Han, Cunbo

AU - Brdar, Slavko

AU - Raasch, Siegfried

AU - Kollet, Stefan

N1 - Funding information: BMBF sponsored this work through the research programme “High Definition of Clouds and Precipitation for Advancing Climate Prediction” (HD(CP)2, grant no. 01LK1506D). The authors would like to thank Matthias Sühring from Leibniz Universität Hannover for reading the manuscript and discussion. We gratefully acknowledge the computing time allowed by the German Climate Computing Centre (DKRZ) on the HPC system Mistral and the Jülich Supercomputing Centre (JSC) on the HPC system JURECA. information Bundesministerium f?r Bildung und Forschung HD(CP)2.BMBF sponsored this work through the research programme ?High Definition of Clouds and Precipitation for Advancing Climate Prediction? (HD(CP)2, grant no. 01LK1506D). The authors would like to thank Matthias S?hring from Leibniz Universit?t Hannover for reading the manuscript and discussion. We gratefully acknowledge the computing time allowed by the German Climate Computing Centre (DKRZ) on the HPC system Mistral and the J?lich Supercomputing Centre (JSC) on the HPC system JURECA.

PY - 2019/4/15

Y1 - 2019/4/15

N2 - The impact of soil moisture heterogeneity on the convective boundary layer (CBL) development was studied. Based on results from large-eddy simulation (LES) applying soil moisture patterns along a river corridor and idealized atmospheric vertical profiles as initial conditions, this study provides insight in the influence of spatial scale of soil moisture heterogeneity on catchment-scale circulations (CCs) and the ensuing growth of the CBL. The simulation results show that the intensity of organized circulations resulting from soil moisture heterogeneity is nonlinearly dependent upon soil moisture heterogeneity scale λ (SMHS) and horizontal gradient. Because of the large SMHS and strong soil moisture contrast, none of the simulations has reached a true steady state even after 24 h of simulation time. The intensity of organized circulations shows a sigmoidal dependence on SMHS. The optimal SMHS for horizontal transport is on the order of 19.2 km, while optimal SMHS for vertical motions occurs at 2.4 km. In these cases, the CCs also exert a strong influence on the boundary-layer structure and the entrainment layer. The potential temperature is not constant with height due to a weak mixing in the boundary layer for large SMHS cases. Differences in sensible heat flux profiles between the heterogeneous cases increase with increasing height and reach a maximum at the top of the CBL. Interestingly, boundary-layer height changes strongly with changing horizontal soil moisture gradient and SMHS while domain means, variances, and amplitudes of land surface energy fluxes are all almost identical. The entrainment flux and subsidence at the top of the CBL are jointly responsible for the CBL height variation.

AB - The impact of soil moisture heterogeneity on the convective boundary layer (CBL) development was studied. Based on results from large-eddy simulation (LES) applying soil moisture patterns along a river corridor and idealized atmospheric vertical profiles as initial conditions, this study provides insight in the influence of spatial scale of soil moisture heterogeneity on catchment-scale circulations (CCs) and the ensuing growth of the CBL. The simulation results show that the intensity of organized circulations resulting from soil moisture heterogeneity is nonlinearly dependent upon soil moisture heterogeneity scale λ (SMHS) and horizontal gradient. Because of the large SMHS and strong soil moisture contrast, none of the simulations has reached a true steady state even after 24 h of simulation time. The intensity of organized circulations shows a sigmoidal dependence on SMHS. The optimal SMHS for horizontal transport is on the order of 19.2 km, while optimal SMHS for vertical motions occurs at 2.4 km. In these cases, the CCs also exert a strong influence on the boundary-layer structure and the entrainment layer. The potential temperature is not constant with height due to a weak mixing in the boundary layer for large SMHS cases. Differences in sensible heat flux profiles between the heterogeneous cases increase with increasing height and reach a maximum at the top of the CBL. Interestingly, boundary-layer height changes strongly with changing horizontal soil moisture gradient and SMHS while domain means, variances, and amplitudes of land surface energy fluxes are all almost identical. The entrainment flux and subsidence at the top of the CBL are jointly responsible for the CBL height variation.

KW - catchment-scale circulation

KW - CBL

KW - LES

KW - soil moisture heterogeneity

UR - http://www.scopus.com/inward/record.url?scp=85062483559&partnerID=8YFLogxK

U2 - 10.1002/qj.3491

DO - 10.1002/qj.3491

M3 - Article

AN - SCOPUS:85062483559

VL - 145

SP - 1218

EP - 1233

JO - Quarterly Journal of the Royal Meteorological Society

JF - Quarterly Journal of the Royal Meteorological Society

SN - 0035-9009

IS - 720

ER -