TY - JOUR

T1 - Key parameters for the life cycle of nocturnal radiation fog

T2 - a comprehensive large-eddy simulation study

AU - Maronga, B.

AU - Bosveld, F. C.

N1 - Funding Information: The first author would like to thank Chiel van Heerwaarden (Wageningen University, Netherlands) and Anton Beljaars (ECMWF, UK) for their continuous support and and many constructive comments during the implementation of the land surface model. Moreover, the first author would thank Siegfried Raasch and Christoph Knigge for various discussions on the subject. This study was funded by the German Research Foundation under grant DFG MA 6383/1-1. All simulations have been performed on the Cray XC-40 at The North-German High Performance Computing Alliance (HLRN), Hannover/Berlin, Germany. We appreciate the two anonymous reviewers for their numerous valuable comments which helped to improve the manuscript. Publisher Copyright: © 2017 Royal Meteorological Society Copyright: Copyright 2017 Elsevier B.V., All rights reserved.

PY - 2017/7

Y1 - 2017/7

N2 - High-resolution large-eddy simulations (LESs) are used to investigate the effect of turbulence as well as the interaction between atmosphere and soil on the life cycle of nocturnal radiation fog. The first part of the article focuses on the validation of the LES model system for simulating radiation fog against measurement data from the meteorological super-site at Cabauw (Netherlands). As in former studies, differences found in the fog life cycle, depth, and liquid water content between LES and observations can be largely ascribed to the presence of local advection processes in the observational data and uncertainty in the measurement data used to initialize the model. Moreover it is found that the choice of the droplet number concentration within the cloud microphysical representation has a high impact on the liquid water content within the fog layer, but a rather small effect on its life cycle. In the second part of the article, a set of LES runs is analysed with idealized initial conditions in order to study the effect of turbulent mixing as well as the initial state of the soil on the development of radiation fog. As expected, the results show that turbulent mixing has a strong impact on the time of fog formation, which is complicated by the interaction with both radiative cooling and water vapour removal by dew deposition. Furthermore, it is found that the near-surface soil temperature plays a key role for the exact time of fog formation, whereas near-surface soil moisture is decisive for the lifting and dissipation time of the fog layer.

AB - High-resolution large-eddy simulations (LESs) are used to investigate the effect of turbulence as well as the interaction between atmosphere and soil on the life cycle of nocturnal radiation fog. The first part of the article focuses on the validation of the LES model system for simulating radiation fog against measurement data from the meteorological super-site at Cabauw (Netherlands). As in former studies, differences found in the fog life cycle, depth, and liquid water content between LES and observations can be largely ascribed to the presence of local advection processes in the observational data and uncertainty in the measurement data used to initialize the model. Moreover it is found that the choice of the droplet number concentration within the cloud microphysical representation has a high impact on the liquid water content within the fog layer, but a rather small effect on its life cycle. In the second part of the article, a set of LES runs is analysed with idealized initial conditions in order to study the effect of turbulent mixing as well as the initial state of the soil on the development of radiation fog. As expected, the results show that turbulent mixing has a strong impact on the time of fog formation, which is complicated by the interaction with both radiative cooling and water vapour removal by dew deposition. Furthermore, it is found that the near-surface soil temperature plays a key role for the exact time of fog formation, whereas near-surface soil moisture is decisive for the lifting and dissipation time of the fog layer.

KW - large-eddy simulation

KW - radiation fog

KW - stable boundary layer

KW - turbulent mixing

UR - http://www.scopus.com/inward/record.url?scp=85029933749&partnerID=8YFLogxK

U2 - 10.1002/qj.3100

DO - 10.1002/qj.3100

M3 - Article

AN - SCOPUS:85029933749

VL - 143

SP - 2463

EP - 2480

JO - Quarterly Journal of the Royal Meteorological Society

JF - Quarterly Journal of the Royal Meteorological Society

SN - 0035-9009

IS - 707

ER -