A satellite‐based climatology of fog and low stratus formation and dissipation times in central Europe

Pauli, Eva; Čermák, Jan; Andersen, Hendrik

doi:10.1002/qj.4272

Cited by 6 publications

(3 citation statements)

References 71 publications

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“…The basis of this study is a satellite-based FLS formation and dissipation time data set which contains information on the timing of the formation and dissipation of FLS for the years 2006-2015 over central Europe. This data set has been created by objectively identifying FLS formation and dissipation on a pixel-by-pixel basis and for each identified FLS event using logistic regression (Pauli et al, 2021;Pauli et al, 2022a). The data basis for this approach, described in Pauli et al (2022b), is an FLS data set derived from the Meteosat Spinning Enhanced Visible and InfraRed Imager (SEVIRI: Egli et al, 2017) with a spatial resolution of 5 km over central Europe.…”

Section: Fog and Low Stratus Formation And Dissipation Time Data Setmentioning

confidence: 99%

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An analysis of fog and low stratus life‐cycle regimes over central Europe

Pauli,

Cermak,

Andersen

et al. 2024

Quart J Royal Meteoro Soc

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A better understanding of fog and low stratus (FLS) life cycles, in particular the typical onset and dissipation times, can help traffic safety and solar power planning. Besides its high dependence on the prevalent meteorological conditions, the FLS life cycle is further determined by the FLS type as well as the underlying geography and climate. While satellite‐based FLS data sets with high temporal and spatial resolution are available, an objective, large‐scale, satellite‐based classification of FLS life‐cycle regions, which would allow for more targeted analyses of the FLS life cycle, is lacking. In this study, a hierarchical clustering algorithm is applied to identify regions of similar relationships of the FLS life cycle to environmental conditions over central Europe. The clustering reveals major FLS life‐cycle regimes with distinct differences in FLS occurrence, temporal FLS life‐cycle patterns, and climatic characteristics. Based on regime‐specific sensitivity analyses, the relationships of the FLS life cycle with near‐ground temperature and specific humidity are identified as the most relevant input relationships for the clustering algorithm, especially in the Mediterranean region. FLS life‐cycle regimes are further presented at a regional scale, outlining the applicability of the derived FLS life‐cycle regimes to future regional process‐oriented FLS life‐cycle studies.

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Section: Fog and Low Stratus Formation And Dissipation Time Data Setmentioning

confidence: 99%

“…Furthermore, fog is influenced by the underlying land‐surface type. An enhancement of fog occurrence has been found over forests (Pauli et al, 2022a), whereas fog cover is reduced in urban areas (Fuchs et al, 2022; Gautam & Singh, 2018).…”

Section: Introductionmentioning

confidence: 99%

An analysis of fog and low stratus life‐cycle regimes over central Europe

Pauli,

Cermak,

Andersen

et al. 2024

Quart J Royal Meteoro Soc

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“…Bergot et al (2015) relied on large eddy simulations (LESs) to characterise the role of dry downdrafts in allowing solar radiation to reach the ground and increase turbulence, leading to the dissipation. Additionally, Pauli et al (2022) studied the climatology of fog and low stratus cloud formation and dissipation times in central Europe using satellite data and showed that fog dissipation is also often related to topography. The dissipation processes are more difficult to study than the fog formation processes due to the complexity of fog's scale.…”

Section: Introductionmentioning

confidence: 99%

Role of thermodynamic and turbulence processes on the fog life cycle during SOFOG3D experiment

Dione,

Haeffelin,

Burnet

et al. 2023

Atmos. Chem. Phys.

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Abstract. In this study, we use a synergy of in situ and remote sensing measurements collected during the SOuthwest FOGs 3D experiment for processes study (SOFOG3D) field campaign in autumn and winter 2019–2020 to analyse the thermodynamic and turbulent processes related to fog formation, evolution, and dissipation across southwestern France. Based on a unique measurement dataset (synergy of cloud radar, microwave radiometer, wind lidar, and weather station data) combined with a fog conceptual model, an analysis of the four deepest fog episodes (two radiation fogs and two advection–radiation fogs) is conducted. The results show that radiation and advection–radiation fogs form under deep and thin temperature inversions, respectively. For both fog categories, the transition period from stable to adiabatic fog and the fog adiabatic phase are driven by vertical mixing associated with an increase in turbulence in the fog layer due to mechanical production (turbulence kinetic energy (TKE) up to 0.4 m2 s−2 and vertical velocity variance (σw2) up to 0.04 m2 s−2) generated by increasing wind and wind shear. Our study reveals that fog liquid water path, fog top height, temperature, radar reflectivity profiles, and fog adiabaticity derived from the conceptual model evolve in a consistent manner to clearly characterise this transition. The dissipation time is observed at night for the advection–radiation fog case studies and after sunrise for the radiation fog case studies. Night-time dissipation is driven by horizontal advection generating mechanical turbulence (TKE at least 0.3 m2 s−2 and σw2 larger than 0.04 m2 s−2). Daytime dissipation is linked to the combination of thermal and mechanical turbulence related to solar heating (near-surface sensible heat flux larger than 10 W m−2) and wind shear, respectively. This study demonstrates the added value of monitoring fog liquid water content and depth (combined with wind, turbulence, and temperature profiles) and diagnostics such as fog liquid water reservoir and adiabaticity to better explain the drivers of the fog life cycle.

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Observations and quantification of fog droplet deposition made during the SOFOG3D campaign

Price

2024

Quart J Royal Meteoro Soc

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This paper presents observations collected during the SOFOG3D campaign in southwestern France during 2019–2020, to elucidate the processes involved in the deposition of fog droplets to the surface, a process that is often modelled in Numerical Weather Prediction models, and forms an important component of the water budget within fog. The study considers that three main mechanisms cause deposition: turbulent, whereby water drops are transported to the surface in turbulent eddies; aerodynamic, whereby the mean horizontal wind deposits droplets directly onto surface canopy elements that protrude into the airflow, and gravitational, whereby droplets fall under the action of gravity directly onto the canopy. Results indicate that the gravitational settling is on average a minor component of the deposition, amounting to around 15% of the total figure. The study also identified that this proportion is relatively larger at 18%, when the turbulence intensity levels are low (vertical‐velocity variance <0.003 m2·s−2). Consequently, for greater values of turbulence intensity the proportion is smaller at 12%. All three deposition processes are studied further using a multiple linear regression of terms against observed water deposition rates, in an attempt to evaluate various methods to estimate the deposition. Results indicate that a simple regression of liquid‐water content against observed deposition has some predictive skill, but that a multiple regression including all three terms produces better results with smaller regression errors. A simpler multiple regression that merged turbulent and aerodynamic terms into a single ‘dynamic’ term produced results almost identical to the three‐term multiple regression. Finally, the differences in fog water deposition rates between stable shallow fog and more turbulent, deeper adiabatic fog were assessed and found to be small. Consequences for parametrisation of liquid‐water deposition in fog are discussed.

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A satellite‐based climatology of fog and low stratus formation and dissipation times in central Europe

Cited by 6 publications

References 71 publications

An analysis of fog and low stratus life‐cycle regimes over central Europe

An analysis of fog and low stratus life‐cycle regimes over central Europe

Role of thermodynamic and turbulence processes on the fog life cycle during SOFOG3D experiment

Observations and quantification of fog droplet deposition made during the SOFOG3D campaign

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