Boundary Layer Parameterizations to Simulate Fog Over Atlantic Canada Waters

Chen, Changshuo; Zhang, Minghong; Perrie, Will; Chang, Rachel; Chen, Xianyao; Duplessis, Patrick; Wheeler, M. J.

doi:10.1029/2019ea000703

Cited by 15 publications

(14 citation statements)

References 47 publications

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“…Both parameterizations of microphysics and boundary layer were chosen as a suitable performance for computational cost and meteorological reproduction (e.g. Chen et al, 2020; Nakanishi & Niino, 2009; Pithani et al, 2019). The gravitational settling of fog droplets was calculated using the fog deposition scheme at the ground surface (Katata et al, 2008) and Duynkerke's (1991) scheme in the atmosphere.…”

Section: Methodsmentioning

confidence: 99%

“…Moreover, the liquid water path (LWP) was used to detect fog layers from possible low clouds located below a few kilometres (e.g. Chen et al, 2020):

LWP = \int_{z_{0}}^{z_{1}} CWC italicdz

Here, CWC is the cloud water content (kg∙m −3 ). The LWP (kg∙m −2 ) is vertical integration of the CWC from the surface of z 0 to approximately 2000 m AGL of the model height z 1 .…”

Section: Methodsmentioning

confidence: 99%

“…Moreover, the liquid water path (LWP) was used to detect fog layers from possible low clouds located below a few kilometres (e.g. Chen et al, 2020):…”

Section: Analysed Variablesmentioning

confidence: 99%

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Numerical simulations of upslope fog observed at Beppu Bay in Oita Prefecture, Japan

Ohashi

Suido

2021

Meteorological Applications

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The present study focussed on the formation of upslope fog. This fog causes chronic expressway closures near Beppu Bay (BB) in Oita Prefecture, Japan. A dense fog event, occurring on 3 and 4 May 2020, resulting from the passage of an extratropical cyclone through the southern Japanese islands, was simulated using the Weather Research and Forecasting (WRF) numerical model. The simulation results indicated that warm and humid air with a lifting condensation level less than 20 m flowed into a plain from BB. Simulated fog and poor visibility were more severe on mountain slope adjacent to BB than on the surroundings. Here, the westward horizontal flux of water vapour by the wind flow was prolonged at lower heights. Analyses of the simulated elements verified that the upslope fog was induced by moist adiabatic cooling of the air lifted by the upslope winds. At the mature stage of upslope fog, a simulated local vertical circulation generated in conjunction with the upper synoptic flow extended the dense fog into the upper atmosphere over BB. During the decaying stage of upslope fog on mountain, a fog covered on the entire BB. This was associated with weakening winds at lower heights. Sensitivity experiments for model boundary conditions supported the importance of mountain steepness and the rectangular shape of BB for the generation of upslope fog. Finally, an application possibility of dense fog forecasts was discussed by using a simulated difference in the equivalent potential temperature between the base of the mountain and Beppuwan expressway interchange located midslope.

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Section: Methodsmentioning

confidence: 99%

“…Moreover, the liquid water path (LWP) was used to detect fog layers from possible low clouds located below a few kilometres (e.g. Chen et al, 2020):

LWP = \int_{z_{0}}^{z_{1}} CWC italicdz

Here, CWC is the cloud water content (kg∙m −3 ). The LWP (kg∙m −2 ) is vertical integration of the CWC from the surface of z 0 to approximately 2000 m AGL of the model height z 1 .…”

Section: Methodsmentioning

confidence: 99%

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Numerical simulations of upslope fog observed at Beppu Bay in Oita Prefecture, Japan

Ohashi

Suido

2021

Meteorological Applications

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“…Chen et al (2020) note problems with too low visibility from their WRF calculations coupled to the Kunkel (1984) visibility equation (vis =ln(ε)/β with the extinction coefficient (km -1 ), β = 144.7 W 0.88 where W is in g m -3 ). The contrast threshold, ε was given as 0.02 by Kunkel but is set to 0.05, as recommended by the WMO (Boudala et al 2012;Chen et al 2020). In the GSD algorithm used in NCEP's Unified Post Processor version 2.2, the Kunkel result is used with ε = 0.02 for visibility reductions in clouds, plus additional effects of aerosol, rainfall and humidity.…”

Section: Visibility Considerationsmentioning

confidence: 99%

Surface deposition of marine fog and its treatment in the WRF model

Taylor

Chen

et al. 2021

Preprint

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Abstract. There have been many studies of marine fog, some using WRF and other models. Several model studies report over-predictions of near surface liquid water content (Qc) leading to visibility estimates that are too low. This study has found the same. One possible cause of this overestimation could be the treatment of a surface deposition rate of fog droplets at the underlying water surface. Most models, including the Advanced Research Weather Research and Forecasting (WRF-ARW) Model, available from the National Center for Atmospheric Research (NCAR), take account of gravitational settling of cloud droplets throughout the domain and at the surface. However, there should be an additional deposition as turbulence causes fog droplets to collide and coalesce with the water surface. A water surface, or any wet surface, can then be an effective sink for fog water droplets. This process can be parameterized as an additional deposition velocity with a model that could be based on a roughness length for water droplets, z0c, that may be significantly larger than the roughness length for water vapour, z0q. This can be implemented in WRF either as a variant of the Katata scheme for deposition to vegetation, or via direct modifications in boundary-layer modules.

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“…Ground-based observations of the boundary layer have higher precision than reanalysis datasets. Previous studies have reported the limitations of ERA-5 in simulating the atmospheric boundary layer (Chen et al 2020a). The boundary layer is crucial in the atmosphere as it helps in dispersing the atmospheric pollutants (Kotthaus et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Impact of Dust Storm on the Atmospheric Boundary Layer over Ahmedabad, a Western Indian Region .

Saha

Sharma

Chhabra

et al. 2021

Preprint

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The present study focuses on investigating the impacts of a sudden dust storm on the atmospheric boundary layer (ABL) over Ahmedabad (23.02°N, 72.57°E), an urban site located in the western region of India. The accumulation of dust in the atmosphere during the dust storm, originating from the Thar Desert in Rajasthan, led to the decrease in surface temperature as a consequence of dust-radiation interaction. Ambient particulate matter data obtained from Air Quality (AQ) station at Ahmedabad showed a spike of 118.5% and 44.5% in PM10 and PM2.5 concentrations, respectively during the event in comparison to the previous control day. Sudden exposure to an anomalous increase in particulate aerosols may cause severe impacts on human health. These surface forcing have been reflected in the stable nocturnal ABL. Backscatter signals recorded by ground-based Ceilometer Lidar at Physical Research Laboratory (PRL), showed that ABL was shallow and collapsed during the dust storm episode. Turbulence was detected in the ABL during the event which further assisted in the vertical mixing of dust aerosols in the ABL. These aerosols got trapped within the residual layer, preventing further percolation in the free atmosphere. Such sub-grid scale changes in the ABL during the dust storm were not reflected in the boundary layer height (BLH) obtained from the ERA-5 reanalysis dataset. A significant association between the ABL and the local radiative budget has been found. It has been substantiated by Coupled Ocean-Atmosphere Radiative Transfer Model (COART) simulations that showed a cooling of the surface. Thus, this study is important as it can be taken as feedback to improve local climate models with respect to dust storm meteorology.

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Boundary Layer Parameterizations to Simulate Fog Over Atlantic Canada Waters

Cited by 15 publications

References 47 publications

Numerical simulations of upslope fog observed at Beppu Bay in Oita Prefecture, Japan

Numerical simulations of upslope fog observed at Beppu Bay in Oita Prefecture, Japan

Surface deposition of marine fog and its treatment in the WRF model

Impact of Dust Storm on the Atmospheric Boundary Layer over Ahmedabad, a Western Indian Region .

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