Variations in the lower level of the PBL associated with the Yellow Sea fog-new observations by L-band radar

Zhang, Suping; Ren, Zhao-Peng; Lu, Shanping; Yang, Yu-Qiang; Wang, Xingong

doi:10.1007/s11802-008-0353-1

Cited by 17 publications

(9 citation statements)

References 13 publications

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“…Remarkably, the simulated seasonal mean profiles at the grids near the two stations are very close to those in observations. Although some differences in inversion strength, the features of both the increase in inversion layer height and the decrease in inversion strength from Cheju to Naze in the simulation period is well reproduced, which is also consistent with the observed climatological distribution (Liu et al, 2016; Zhang et al, 2008; Zhang et al, 2009).…”

Section: Resultssupporting

confidence: 86%

Transition of Low Clouds in the East China Sea and Kuroshio Region in Winter: A Regional Atmospheric Model Study

et al. 2020

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Bias in simulating the stratocumulus‐to‐cumulus transition remains a main source of uncertainties in climate projection and can significantly affect the energy budget in climate models. To gain insights into the transition, this study investigates the cloud transition forced by the sea surface temperature (SST) front and synoptic disturbances in the East China Sea and Kuroshio region in winter based on both observations and regional atmospheric model simulations. The Kuroshio SST front greatly accelerates cloud transition by enhancing surface latent heat flux, marine atmospheric boundary layer (MABL) dynamical adjustment, and cloud top entrainment. With the sharp SST increase from the cold flank to the Kuroshio SST warm tongue (KWT), surface wind convergence (SWC) over the KWT induced by the SST front and synoptic disturbances enhances the coupling between the cloud layer and subcloud layer. An underlying positive feedback between the SWC and latent heating in the cloud layer can enhance abrupt change in cloud properties and maintain cloud band over the KWT against the decoupling through the so‐called “Deepening‐Warming” mechanism induced by latent heating. From the KWT downwind southward, the surface layer turbulent mixing weakens, while latent heating in the cloud layer and cloud top longwave radiative cooling enhance buoyancy and vertical mixing in the cloud layer. This difference in vertical mixing between the cloud layer and subcloud layer facilitates the MABL decoupling and impedes upward moisture transport. Meanwhile, decreasing lower tropospheric stability is conducive to the entrainment of drier and warmer air from above into the cloud layer, strengthening cloud evaporation.

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Section: Resultssupporting

confidence: 86%

Transition of Low Clouds in the East China Sea and Kuroshio Region in Winter: A Regional Atmospheric Model Study

et al. 2020

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“…The vertical development of sea fog layer is highly correlated with the atmospheric stratification near the fog top (Zhang et al, ). To identify the observed stratification within the sea fog layer, two stations where sea fog occurred, DFH2 and CS, are selected (Figures a–d).…”

Section: Improvements Of Sea Fog Simulation Caused By the Top‐driven mentioning

confidence: 99%

The Impact of Turbulent Diffusion Driven by Fog‐Top Cooling on Sea Fog Development

Yang

Gao

2020

JGR Atmospheres

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Turbulent mixing driven by cloud/fog‐top radiative and evaporative cooling (hereafter top‐driven diffusion), including top‐down mixing and top‐cooling entrainment, is critical for the development of cloud/fog. Previous work mainly focused on impacts of top‐driven diffusion on stratocumulus‐topped planetary boundary layer (PBL) and radiation fog over land. However, its exact role in sea fog process is yet unclear. Using the Weather Research and Forecasting (WRF) model with the updated Yonsei University (YSU) PBL scheme, in which the ysu_topdown_pblmix option is responsible for the parameterization of the top‐driven diffusion, the present study investigates respective effects of the top‐cooling entrainment and top‐down mixing on an advection fog event over the Yellow Sea that occurred on 20–21 May 2014. Evaluation of the modeling results confirms that the top‐driven diffusion significantly improves the sea fog simulation. The top‐cooling entrainment allows more relatively quiescent air above the fog top to mix into the sea fog layer, leading to a higher mixed layer with increased temperature and decreased humidity. With the enhancement of buoyant turbulence, the warming and dehumidifying moderately lift the sea fog bottom and reduce the false fog area. The top‐down mixing performs quite well in reproducing a stable structure near the fog top, which results from the added turbulent mixing determined by a revised K profile. Note that the effect of top‐driven diffusion shows high sensitivities to shortwave radiation and vertical resolution. Besides the fog‐top cooling, the fog‐droplet sedimentation is necessary to be included in the top‐cooling entrainment.

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“…We used codes 46 and 47 to represent the existence of fog (Table 1). The dissipation stage of fog was excluded since the synoptic condition may be changed (Zhang et al, 2008;Guo et al, 2015). The study area covers 171 °W-130 °W, 39 °N-55 °N with a total of 42242 reported fog points (defined as fog cases).…”

Section: Data and Methods 21 Datamentioning

confidence: 99%

“…Turbulence plays an important role in the formation of fog (Koračin et al, 2005;Guo et al, 2015;Huang et al, 2015). The bulk Richardson number (Ri) can be used as a measure of Frontiers in Earth Science frontiersin.org turbulence (Zhang et al, 2008;Huang et al, 2011;Kim and Yum, 2012):…”

Section: Methodsmentioning

confidence: 99%

Atmospheric conditions conducive to marine fog over the northeast Pacific in winters of 1979–2019

Zhang

Koračin

et al. 2022

Front. Earth Sci.

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Observations show that the northeast Pacific (NEP) is a fog-prone area in winter compared with the northwest and central Pacific where fog rarely occurs in winter. By synthesizing observations and reanalysis results from 1979 to 2019, this study investigates the atmospheric circulation and marine atmospheric boundary layer structure associated with marine fog over the NEP in winter. Composite analysis shows that the eastern flank of the Aleutian low and the northwestern flank of the Pacific subtropical high jointly contribute to a northward air flow over the NEP. Under such conditions, warm and moist air flows through a cooler sea surface and facilitates the formation of advection-cooling fog. The air near the sea surface in foggy areas is cooled by the downward sensible heat flux. The smaller upward latent heat flux (∼10 W m−2) compared to the surrounding area (>60 W m−2) demonstrates that the moisture originates from the advection instead of local evaporation. The lower (at 925 to 875 hPa) and stronger (up to 0.08 K hPa−1) inversion layer, compared with cloudy cases and the turbulence in the lower atmosphere (below 975 hPa), also promotes fog formation and evolution. Approximately 68% of all fog cases (42242) show positive differences between surface air temperature (SAT) and sea surface temperature (SST), while 32% are negative, during southerly winds. Composite analysis of the latter shows lower specific humidity above the inversion bottom compared to the former. Dry air enhances longwave radiative cooling from the fog top, favoring cooling of the fog layer, gradually causing SAT to fall below SST.

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Variations in the lower level of the PBL associated with the Yellow Sea fog-new observations by L-band radar

Cited by 17 publications

References 13 publications

Transition of Low Clouds in the East China Sea and Kuroshio Region in Winter: A Regional Atmospheric Model Study

Transition of Low Clouds in the East China Sea and Kuroshio Region in Winter: A Regional Atmospheric Model Study

The Impact of Turbulent Diffusion Driven by Fog‐Top Cooling on Sea Fog Development

Atmospheric conditions conducive to marine fog over the northeast Pacific in winters of 1979–2019

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