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The Bessel beams scattering of the fog particles were calculated by using the plane beams angle spectrum expansion method, and the effects of the topological charge and the half-conic angle of the Bessel beam on the differential scattering cross-section were analyzed by numerical calculation. Based on the scattering results of a single fog particle by a Bessel beam, by Monte Carlo method, the propagation characteristics of the Bessel beam in fogs with different visibility are simulated, and the effects of the wavelength, topological charge and semi-conic angle of the Bessel beam on transmissivity and reflectivity are analyzed. The studies show the self-healing ability of the Bessel beams, and the propagation distance of the Bessel beam is longer than that of the plane beams in fogs. [ABSTRACT FROM AUTHOR]

Using 22‐year ground observations on meteorological variables, we conducted a statistical analysis to reveal fog characteristics at Shanghai Pudong International Airport (SPIA). Fog events were classified by fog types using an objective method. Two types of advection fogs are dominant in fog events at SPIA, followed by radiation fogs. Different fogs have evident annual and monthly variations in frequency. Advection fog mostly appear from February to April, while radiation fog is mainly between November and February. Six synoptic patterns associated with fogs were determine by a self‐organizing maps cluster method, two of which, namely 'west of marine high pressure' and 'inverted trough', are most favourable for the formation of advection fogs, whereas 'bottom of weak cold high‐pressure' is favourable for radiation fogs. The frequency of advection fog occurrence exhibits temporal fluctuations with distinct peaks occurring 2–3 h after sunset, around midnight, and 1–2 h before sunrise, while almost all radiation fog occur in the second half of the night, and favourable conditions for fog onset become more effective with the length of the night. Radiation fog exhibits a longer duration than advection fog and tends to result in lower visibility. The prevalent wind direction for the formation of advection fog is generally from the east to the southeast, whereas radiation fog is typically associated with westerly winds. The temperature and air pressure during the formation of both advection and radiation fogs follow a normal distribution in most seasons. More fog characteristics were categorized by fog types and seasons. [ABSTRACT FROM AUTHOR]

The advection fog characteristics at Qingdao Liuting International Airport during 2000–2022 are studied based on surface observation, sounding and reanalysis data. Surface observation data show that there were two types of fog: evaporation fog (EF) dominated by northwesterly wind in winter and cooling fog (CF) dominated by southeasterly wind in spring and summer. CF is thicker than EF due to different planetary boundary layer (PBL) structures. For EF, the middle and low troposphere are affected by dry and cold air, while CF is affected by warm and moist air below 850 hPa. When EF formed, downdrafts and a positive vertical gradient of the pseudo-equivalent potential temperature indicate stable PBL, surface heat flux is upward from sea to atmosphere and surface wind diverges near the air–sea interface. When CF formed, these characteristics are reversed. Fog is significantly affected by sea–land–atmosphere interactions. The moisture source is mainly from surface fluxes released by the Yellow Sea in the case of EF, while it is from moist air at low latitudes and local land transpiration in the case of CF. The difference in temperature between the sea surface and surface air changes from the range of 0–8 K for EF but from −4–0 K for CF. [ABSTRACT FROM AUTHOR]

Fog may continue to inhibit industry in the future. Here, we focused on a specific advection fog event in Shanghai, China, and applied a pseudo global warming method to examine advection fog under the RCP8.5 high-emission scenario. The method involved downscaling the future atmospheric conditions over the ensemble average of 19 global climate models from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). We used the Weather Research and Forecasting Model coupled with a single-layer urban canopy model (WRF—UCM) to run four sensitivity experiments and examined the advection fog and its relationship to changes in meteorological conditions. The results showed that: 1) The advection fog event tended to remain in Shanghai despite global warming; 2) advection fog will not change greatly in the future; however, the onset and dissipation times will change slightly; 3) relative humidity (RH) locally increases prior to the onset of the advection fog, and decreases at the dissipating stage, despite the current and future experiments having the same RH initial and boundary conditions; 4) a small increase in surface air temperature and an increase in RH contribute to the early advection fog onset, and vice versa. Windspeed facilitates the early onset and dissipation of advection fog. [ABSTRACT FROM AUTHOR]

A study on fog‐water collection potential at the Mediterranean Iberian Peninsula was carried out for the period 2003–2012. The area is denoted by a high population density, with fairly common water restrictions in certain periods during the year. Moreover, climate change projections point out a sharp drop in precipitation for this sector of the western Mediterranean Basin that would aggravate water problems. This work aims to look closely at knowledge of fog‐water collection and it presents results about: its behaviour during different seasons of the year; the fog‐water collection potential on dry days (precipitation <1 mm); the influence of site elevation on both collected volumes and the number of days with fog‐water collection. To do so, daily fog‐water collection data were analysed from 2003 to 2012 with a dense network of 23 fog‐water collectors, which run along the Mediterranean coast of the Iberian Peninsula. The most relevant results were: (a) the seasonal periods with the largest recorded fog‐water volumes were autumn and spring; the highest percentages of days with fog‐water collection were obtained in summer and autumn; (b) on days when precipitation was null or negligible (<1 mm), maximum daily fog‐water captures were considerable and exceeded 25 L m−2 at more than half the studied sites; (c) the greater the positive difference in elevation between nearby stations, the larger the positive difference in both fog collected volumes and fog days at equal exposition to prevailing winds, differences that increase in the summer period. Mount Muela (Murcia Region), combining a pair of stations only distanced by 600 m but at a 92‐m elevation difference, reported a contrast of two times the collected volume at the upper station compared to the lower and an increment of 61% more days with fog occurrence. Mount Montseny (Catalonia), with a pair of stations distanced by 1,600 m horizontally and 398 m in elevation difference, obtained a sixfold variation between stations for fog‐water collection and a 73% increment in foggy days. [ABSTRACT FROM AUTHOR]

The presence of fog reduces the horizontal visibility to less than 1000 meters and disrupts air transport services and can make it impossible for aircraft to land and take off. Climatology of fog can help better diagnosis and prediction of fog. In this study, METAR data from 2011 to 2020 were used to detect fog events at Ardebil Airport and according to the classification algorithm of Tardif and Rasmussen (2007), the types of events were determined. Then the fog climate was studied during the period. The results showed that the most common type of fog at Ardebil Airport is radiation fog and the rarest type is precipitation fog. In terms of duration of fog event, radiation fog was the longest fog event and precipitation fog was the shortest fog event. The highest incidence of fog during the study years was at 3 and 4 GMT. The monthly distribution of radiation fog showed that events often occurred in autumn and early winter (September to December). In terms of annual changes in the occurrence of fog, there was no significant trend in the number of fog hours during the studied years, except for the last three years which had a decreasing trend.

Copyright of Anuario do Instituto de Geociencias is the property of Universidade Federal do Rio de Janeiro, Instituto de Geociencias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study investigates the predictability of the dense advection fog over Istanbul on February 19, 2014, which significantly halted international as well as local transportation. Sensitivity simulations were conducted using the Weather Research and Forecasting (WRF) model forced by the ERA-Interim reanalysis data. A hierarchical approach was adopted. The first group of sensitivity simulations involving different microphysics schemes (WSM6, Morrison, Thompson-aerosol, NNSL, NNSL-CCN, and Milbrandt) indicated that the simulation with Milbrandt reproduced slightly better results for the fog event. Further sensitivity tests involving different planetary boundary layer (PBL) schemes (ACM2, BouLac, MYJ, MYNN2.5, MYNN, and YSU) were conducted. The YSU PBL scheme provided better diurnal air and dew point temperature variations compared to the observations at Ataturk and Sabiha Gokcen airports. We further investigated the performances of RRTMG, RRTMG-fast and Dudhia shortwave radiation schemes, and RRTMG and RRTM longwave radiation schemes. Our analyses revealed that simulation of the fog was very sensitive to radiation scheme. Although all PBL schemes were able to generate fog, a configuration with the YSU PBL scheme with Dudhia shortwave and RRTM longwave schemes produced comparatively low RMSE for temperature depression, 0.31 °C (0.23 °C), during the fog hours at Sabiha Gokcen (Ataturk) Airport. The model simulated the onset time of the afternoon fog well; however it reproduced the onset and dissipation times of the morning fog earlier than the observations. It is also found that the use of high-resolution initial and boundary condition data did not provide a significant improvement in the advection fog simulation. [ABSTRACT FROM AUTHOR]

Low visibility conditions due to fog affect air traffic and, in some cases, are the leading cause of aviation accidents. Accurate forecasting of fog can lead to a significant reduction of human and financial losses. Numerical weather prediction (NWP) models have limitations in simulating fog accurately for operational purposes. However, recent studies have confirmed that ensemble‐based forecasts are effective in fog forecasting. In this study, a multi‐physics ensemble prediction system (EPS) was used to simulate the occurrence of several radiation, cloud base lowering (CBL), and advection fog events that occurred at Arak, Ardebil, Hamedan, Orumiyeh, Rasht and Shahrekord airports located across Iran, during January and December 2015. The multi‐physics EPS including a reference deterministic forecast consists of 16 different configurations of the weather research and forecasting (WRF) model and was run from 12 UTC 12 January to 12 UTC 16 January 2015 and from 00 UTC 27 December to 12 UTC 31 December 2015 to simulate fog occurrences at six airports. SW99 and G2009 visibility algorithms were applied to the EPS outputs to predict the fog. The advantages of probabilistic fog forecasting in this study were shown by comparing the reference forecast and the ensemble‐based forecasts of fog events. The results showed that by considering a probability threshold of 37.5%, 50% and 62.5% for the ensemble forecasts, the EPS outperformed the deterministic fog forecasts obtained from a deterministic reference forecast. Such that, with 37.5% and 50% probability thresholds, the equitable threat score (ETS) was much higher than the ETS for the reference deterministic fog forecast. Also, the EPS with 37.5% and 50% probability thresholds could correctly predict 3 and 4 (out of 10) more fog events compared with the reference deterministic forecast. [ABSTRACT FROM AUTHOR]

Advection fog processes produce frequent low cloud and fog (LCF) during summer along the coast of central and northern California. Four radiometer datasets from sites in San Francisco and Monterey Bay as well as fog-drip and meteorological observations were used to characterize the role of LCF on surface radiation budget components and scattering of solar radiation. LCF produced distinct and consistent impacts on surface radiation relative to clear skies including large reductions (approximately half) in solar irradiance but large increases (approximately 180%) in the diffuse beam component, consistent increases of approximately 70 W m−2 in down-welling longwave radiation (L↓), as well as reductions in net radiation and leaf surface temperature by day and increases at night. L↓ can be a useful and accurate tool for monitoring the presence of LCF, using simple thresholds: LCF = L↓ > 360 W m−2 and clear-sky = L↓ < 340 W m−2. Based on this, LCF conditions prevailed 60% of hours during summer, peaking consistently at 08:00 PDT, with clear skies occurring 33% and mixed conditions 7% of hours. The ratio of the incident surface to extraterrestrial solar radiation (τ) is also useful to determine LCF presence during daylight hours, using LCF = τ < 0.0059β + 0.3 and clear-sky = τ > 0.0059β + 0.3, where β is the solar elevation angle. We also present a model to partition the diffuse and direct beam fractions of solar irradiance specifically for coastal LCF, which improved accuracy by more than 10% relative to existing universal models. These radiation characteristics are important for understanding energy balance and sunlight conditions experienced by coastal ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Advection fog is the sole source of water for many near-the-sea arid areas worldwide such as the lomas , i.e. fog-dependant landscapes of the coastal zone of Peru and Northern Chile, where deforestation occurred since 16th century, leading to a progressive and severe desertification. There, today's local socio-ecological systems suffer from lack of freshwater because they cannot rely anymore on the contribution of fog captured by vegetation. This paper presents the results of an experimental reforestation project carried out in Mejia (Peru), where tree seedlings of five native and exotic species were planted in two permanent plots in 1996. Part of the seedlings were irrigated during the first three years after planting, others not. The irrigation was carried out thanks to water harvesting by large fog collectors. From the third year onwards, all trees relied only on fog water collected by their canopy. Survival rate, height, and root-collar diameter were monitored until 2010, when also the soil carbon and nitrogen stocks were measured. Fifteen years after the planting, about 65% of trees were still alive and growing, and reforestation had induced substantial carbon sequestration both above- and below-ground. Of the tree species, Acacia saligna was definitely best performing than the other, with most of the above ground carbon stored in its biomass and a consequent high efficiency as natural fog collector. Overall, the combination of fog collection by nets and the plantation of trees showing good fog collection capacity, represented a successful strategy for allowing reforestation of arid environments and induced fast and substantial carbon sequestration. Greater efforts should be thus devoted for this purpose, paying special attention to the selection of the most suitable tree species to plant, especially looking at the local biodiversity. This work is dedicated to the memory of Professor Mario Falciai, passed away in 2015, who firstly conceived the experiment and attended all the work since 1996, bringing in our University the idea of Fog Collection for sustainable water management. Graphical abstract Unlabelled Image Highlights • Advection fog is the sole source of water for many near-the-sea areas worldwide. • We present the results of a long-term reforestation project in the Atacama Desert. • Trees were irrigated with artificially fog-collected water for three years. • After 15 years from planting, about 65% of trees were still alive and growing. • Reforestation induced fast and substantial carbon sequestration. [ABSTRACT FROM AUTHOR]

Abstract: Advection fog occurs usually when warm and moist air flows over cold sea surface. It is occasionally reported that the fog air temperature falls below sea surface temperature (called here the sea fog with sea surface heating [ssH]) due to longwave radiation cooling at fog top. Using 8‐year buoy observations, this study reveals that about 33% of the time, the advection fog is with ssH in the western Yellow Sea. By synthesizing long‐term observations from meteorological stations, atmospheric soundings, and offshore buoys, this study further investigates the marine atmospheric boundary layer (MABL) structure and atmospheric circulation associated with the ssH sea fog. Composite analysis shows that a local anomalous high pressure favors widespread formation of the ssH sea fog. The subsidence in the high pressure intensifies the thermal and moist stratification between the MABL and free atmosphere through adiabatic warming. The dry air above helps cool the fog layer by enhancing the longwave radiative cooling at the fog top and the vertical mixing beneath, causing air temperature to drop below sea surface temperature. The ratio of sea fog with ssH to total sea fog decreases from spring to summer as the descending motion and MABL stratification both weaken. This study highlights the importance of longwave radiative cooling at the advection fog top and suggests a way to improve sea fog forecast in the Yellow Sea. [ABSTRACT FROM AUTHOR]

A series of numerical simulations is conducted to understand the formation, evolution, and dissipation of an advection fog event over Shanghai Pudong International Airport (ZSPD) with the Weather Research and Forecasting (WRF) model. Using the current operational settings at the Meteorological Center of East China Air Traffic Management Bureau, the WRF model successfully predicts the fog event at ZSPD. Additional numerical experiments are performed to examine the physical processes associated with the fog event. The results indicate that prediction of this particular fog event is sensitive to microphysical schemes for the time of fog dissipation but not for the time of fog onset. The simulated timing of the arrival and dissipation of the fog, as well as the cloud distribution, is substantially sensitive to the planetary boundary layer and radiation (both longwave and shortwave) processes. Moreover, varying forecast lead times also produces different simulation results for the fog event regarding its onset and duration, suggesting a trade-off between more accurate initial conditions and a proper forecast lead time that allows model physical processes to spin up adequately during the fog simulation. The overall outcomes from this study imply that the complexity of physical processes and their interactions within the WRF model during fog evolution and dissipation is a key area of future research. [ABSTRACT FROM AUTHOR]

A large quantity of advection fog appeared in the Yangtze River delta region between 1 and 2 December 2009. Here, we detail the fog formation and dissipation processes and the background weather conditions. The fog boundary layer and its formation and dissipation mechanisms have also been analyzed using field data recorded in a northern suburb of Nanjing. The results showed the following: (1) This advection fog was generated by interaction between advection of a north-east cold ground layer and a south-east warm upper layer. The double-inversion structure generated by this interaction between the cold and warm advections and steady south-east vapour transport was the main cause of this long-lasting fog. The double-inversion structure provided good thermal conditions for the thick fog, and the south-east vapour transport was not only conducive to maintaining the thickness of the fog but also sustained its long duration. (2) The fog-top altitude was over 600 m for most of the time, and the fog reduced visibility to less than 100 m for approximately 12 h. (3) The low-level jet near the lower inversion layer also played a role in maintaining the thick fog system by promoting heat, momentum and south-east vapour transport. [ABSTRACT FROM AUTHOR]

Abstract: Sea fog occurs frequently over the Yellow Sea in spring and summer, which causes costly or even catastrophic events including property damage, marine accidents, public health and financial losses. Case studies of advection and steam fogs using direct observation over the sea are constructed to better understand their formation, evolution and dissipation. A southerly wind supplies moisture to initiate advection fog events (AFs). Approximately −100 to −200W m−2 of latent heat flux and −70W m−2 of sensible heat flux during mature AFs are characterized with stable stratification which maintains dense fog by limiting downward mixing of dryer air. Steam fogs (SFs) develop from flow of cold air over warmer water, but are normally of limited persistence. During the SFs, a northerly wind decreases the air temperature below the sea surface temperature, which increases the relative humidity through evaporation from the warmer ocean. During mature SF, 360W m−2 of latent heat flux and 150W m−2 of sensible heat flux are characterized with neutral and unstable atmospheric conditions. The increase in wind speed and wind shear mixes dry air downward to the surface and limits the duration of the SF. [Copyright &y& Elsevier]

• Isotope-based fog classification is consistent with meteorological-based fog classification. • Isotope hydrology suggests fog formation is dynamic and can include isotopic evolution. • Line conditioned excess is a useful tool in differentiating fog types. • Fog type should be taken into account for accurate modelling of global climate change impacts on fog dependent ecosystems. Although fog is an important component of the hydrological cycle of drylands, its formation mechanisms are not fully understood leading to discrepancy of fog type classifications using different methodologies. Such discrepancies may result in under or over estimation of the potential impacts of global climate change on the ecohydrology of fog dependent ecosystems. To fill this knowledge gap, this study applies hydrogen and oxygen stable isotopes to objectively classify fog and compares this classification to meteorological conditions defined for the formation of these fog types. Results suggest that this isotope based fog classification method is consistent with expected meteorological conditions for the different fog types such as radiation fog, advection fog and mixed fog. Wind speeds decreased from advection, to radiation fog while estimated fog (cloud) height was lowest during radiation fog and highest during advection fog. In addition, precipitation-offset (lc-excess) suggests that radiation and advection fog had different moisture sources, with radiation fog being locally sourced and advection fog originating from the ocean. This study suggests isotope-based fog classification is an objective method that could be applied to other coastal fog dependent ecosystems to help assess the potential impact of climate change on these ecosystems. [ABSTRACT FROM AUTHOR]

This note describes a numerically stable version of the improved Mellor–Yamada (M–Y) Level-3 model proposed by Nakanishi and Niino [Nakanishi, M. and Niino, H.: 2004, Boundary-Layer Meteorol. 112, 1–31] and demonstrates its application to a regional prediction of advection fog. In order to ensure the realizability for the improved M–Y Level-3 model and its numerical stability, restrictions are imposed on computing stability functions, on L/ q, the temperature and water-content variances, and their covariance, where L is the master length scale and q 2/2 the turbulent kinetic energy per unit mass. The model with these restrictions predicts vertical profiles of mean quantities such as temperature that are in good agreement with those obtained from large-eddy simulation of a radiation fog. In a regional prediction, it also reasonably reproduces the satellite-observed horizontal distribution of an advection fog. [ABSTRACT FROM AUTHOR]

The goal of this study is twofold. First, we verify the retrievals of temperature and humidity profiles from a ground-based microwave radiometer (MWR) using radiosonde soundings. Second, we assess the potential of the MWR to nowcast fog formation and dissipation in a hyper-arid environment through the analysis of its profiles. The MWR is installed and operated at Masdar Institute in Abu Dhabi, United Arab Emirates (UAE), adjacent to Abu Dhabi's International Airport. MWR observations collected from 18 February 2017 to 31 March 2019. A comparison with airport radiosonde data reveals a good agreement in particular for temperature, with the two measurements generally within 1 K from the surface to 10 km. For the specific humidity, the biases can reach 5 g kg−1 in the PBL. Biases can be attributed to errors in the radiosonde measurements and a non-optimized retrieval algorithm for the MWR. A total of 14 fog events are identified during the study period. A strong near-surface inversion with lapse rates in the lowest 250 m of up to 30 K km−1 is needed for fog to form. Subsidence warming and drying associated with the subtropical anticyclone can descend down to 500 m, aiding the formation of fog at night. Cloud base height retrievals from the infrared (IR) camera capture fog onset and dissipation and complement the MWR observations. A synergy of different instruments could allow for more accurate fog detection. • A comparison of microwave radiometer (MWR) and radiosonde temperature profiles reveals a good agreement. • The average Convective Boundary Layer height derived from MWR at measurement location is around 1.6 km. • Strong surface-based inversion and near-surface water vapour mixing ratio of at least 6 gm kg-1 needed for fog to occur. [ABSTRACT FROM AUTHOR]