Characteristics Of Fog Research Articles

西双版纳热带雨林和哀牢山亚热带常绿阔叶林雾特征研究

PDF HTML阅读 XML下载 导出引用 引用提醒 西双版纳热带雨林和哀牢山亚热带常绿阔叶林雾特征研究 DOI: 10.5846/stxb201806291435 作者: 作者单位: 中国科学院大学，中国科学院热带森林生态学重点实验室,中国科学院热带森林生态学重点实验室,中国科学院热带森林生态学重点实验室,中国科学院热带森林生态学重点实验室，中国科学院西双版纳热带雨林生态系统研究站,环境激素与生殖发育安徽省重点实验室，阜阳师范学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2016YFC0502105）；国家自然科学基金（41671209，31600390）；国家自然科学基金与云南省联合项目（U1602234） Characteristics of fog in Xishuangbanna tropical rainforest and Ailaoshan subtropical evergreen broad-leaved forest Author: Affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun Yunnan,Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun Yunnan,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以西双版纳热带雨林和哀牢山亚热带常绿阔叶林为研究对象，利用PWS100天气现象仪获取两种森林类型的能见度数据。基于2014年西双版纳热带雨林和哀牢山亚热带常绿阔叶林的能见度数据，对两种森林类型雾的特征进行定量研究。研究结果表明：（1）西双版纳热带雨林全年雾日数为196 d，占全年的53.7%，哀牢山亚热带常绿阔叶林全年雾日数为100 d，占全年的27.4%，热带雨林全年雾日数几乎为亚热带常绿阔叶林雾日数的两倍；（2）热带雨林雨季和干季各占28.06%和71.94%，而亚热带常绿阔叶林雨季和干季各占72%和28%；（3）热带雨林一日内雾持续的最长时间为10.5 h，而亚热带常绿阔叶林雾生成和消散时间不定，一日内雾最长持续时间可达24 h，但雾发生的频率低于西双版纳热带雨林。两种森林类型全年雾日特征有明显的差异性，通过定量评价地处过渡带上的两种多雾森林生态系统雾特征，可为未来气候变化对不同森林生态系统碳水交换影响提供数据支撑。 Abstract:Using the Xishuangbanna tropical rain forest and the Ailaoshan subtropical evergreen broad-leaved forest as the research objects, the PWS100 was used to obtain visibility data for the two forest types. Based on the visibility data of the two types of forest, we quantitatively studied the fog characteristics. The results showed that:(1) In 2014, the number of foggy days in the Xishuangbanna tropical rain forest was 196 d, accounting for 53.7% of the whole year. The number of foggy days in the subtropical evergreen broad-leaved forest in Ailaoshan was 100 d, accounting for 27.4% of the whole year. The number of foggy days in the rain forest was almost twice that of the subtropical evergreen broad-leaved forest; (2) The rainy season and the dry season in the tropical rain forest accounted for 28.06% and 71.94%, respectively. The subtropical evergreen broad-leaved forests accounted for 72% and 28%, respectively. (3) The time of generation and dissipation of fog within the tropical rain forest had certain regularity. Generally, the fog formed at night and dissipated the next morning, the longest time of one day's fog was 10.5 h. The fog generation and dissipation time of subtropical evergreen broad-leaved forest was indefinite, and the maximum duration of fog in one day reached 24 h; however, the frequency of fog was lower than that of Xishuangbanna. There were obvious differences between the two types of forest in the annual fog days. The quantitative assessment of the fog characteristics of the two types of foggy forest ecosystems could provide data in support of future climate change effects on the exchange of carbon and water in different forest ecosystems. 参考文献 相似文献 引证文献

Impact of Natural and Anthropogenic Factors on Fog Frequency and Variability in Kraków, Poland in the Years 1966–2015

The aim of the study was to determine the long term variability of fog occurrence in Krakow in the light of the changeability of fog favoring factors. The annual number of days with several fog characteristics was studied for the period 1966–2015, using data from two meteorological stations located in the city center and in the suburbs. For all these data series on fog, a strong decrease was observed in the study period, i.e., the number of days with fog decreased on average by about 60%, with the tendency being more distinct in the city center. Fog favoring conditions were determined by atmospheric circulation, wind speed, relative humidity, urban heat island (UHI) and air pollution and correlated with data on fog. Results statistically significant at p < 0.01 show that the relationship is the strongest between fog frequency and air pollution. However, as the air pollution levels decreased, especially after the change of political and economic system in 1989, environmental factors became decisive in controlling fog occurrence. Although the role of atmospheric circulation in fog formation is unquestionable, fog favoring circulation types (Sa, SWa, Ca, Ka) show no meaningful tendency and no significant correlation with long-term fog occurrence frequency. Therefore, decreasing trends in days with low wind speed and in days with relative humidity RH ≥ 80% and RH ≥ 95% are considered as additional factors which contributed to the observed fog frequency decrease. UHI showed no impact on fog frequency as in Krakow relief modified UHI (RMUHI) is observed and no significant changes in the part of UHI defined for the lowest part of the city were observed.

Observation Analysis on Microphysics Characteristics of Long-lasting Severe Fog and Haze Episode at Urban Canopy Top

A field experiment based in a 255 m meteorological tower in Tianjin was conducted from Dec. 29, 2016 to Jan. 8, 2017, to study microphysical characteristics of the urban canopy top and their effect on a long-lasting severe Haze and Fog (HF) episode. The results show that the gradients of the PM2.5 concentration in the vertical direction varied greatly during the clean days but less so during HF days, which was consistent with the variation in the PBL height and turbulent activity. During HF1-1, PM2.5 concentrations at 120 m were obviously higher than those at the surface and at 200 m. Wind shear was one of the important factors due to the accumulation of pollutants at 120 m. During HF1-2, PM2.5 concentrations at the three levels declined with a mode of “cliff.” The vertical gradient of concentrations between 120 and 200 m was small, but it was larger between the surface and 120 m. The wet scavenging effect of the fog, the damaged inversion layer, and the strengthened turbulence were closely related to the “cliff” decline in concentration. When the fog transformed into haze during HF1-3, the turbulent energy rapidly decreased, and the atmospheric layer again became stable, with the height of the PBL being nearly 120 m.

Assessment of the Suitability of Fog Computing in the Context of Internet of Things

This work performs a rigorous, comparative analysis of the fog computing paradigm and the conventional cloud computing paradigm in the context of the Internet of Things (IoT), by mathematically formulating the parameters and characteristics of fog computing—one of the first attempts of its kind. With the rapid increase in the number of Internet-connected devices, the increased demand of real-time, low-latency services is proving to be challenging for the traditional cloud computing framework. Also, our irreplaceable dependency on cloud computing demands the cloud data centers (DCs) always to be up and running which exhausts huge amount of power and yield tons of carbon dioxide ( $\text{CO}_2$ ) gas. In this work, we assess the applicability of the newly proposed fog computing paradigm to serve the demands of the latency-sensitive applications in the context of IoT. We model the fog computing paradigm by mathematically characterizing the fog computing network in terms of power consumption, service latency, $\text{CO}_2$ emission, and cost, and evaluating its performance for an environment with high number of Internet-connected devices demanding real-time service. A case study is performed with traffic generated from the $100$ highest populated cities being served by eight geographically distributed DCs. Results show that as the number of applications demanding real-time service increases, the fog computing paradigm outperforms traditional cloud computing. For an environment with $50$ percent applications requesting for instantaneous, real-time services, the overall service latency for fog computing is noted to decrease by $50.09$ percent. However, it is mentionworthy that for an environment with less percentage of applications demanding for low-latency services, fog computing is observed to be an overhead compared to the traditional cloud computing. Therefore, the work shows that in the context of IoT, with high number of latency-sensitive applications fog computing outperforms cloud computing.

Study on the Scattering Effect of Terahertz Waves in Near-Surface Atmosphere

Terahertz waves suffer from scattering attenuation of various types of particles due to the complex environment in the near-surface atmosphere. This paper focused on the scattering attenuation of terahertz waves due to different kinds of particles, including droplets, haze particles, and raindrops. The optical parameters of these particles were determined by meteorological data and the related literature. The characteristics of the scattering attenuation of terahertz waves on hazy days were analyzed using Rayleigh scattering and the lognormal distribution of particles, based on different levels of pollution and frequency. The basic physical characteristics of fog were also examined to determine the influence of water content on the visibility and size distribution of droplets. The scattering characteristics of terahertz waves caused by advection fog and radiation fog were assessed using the Mie scattering theory based on the complex index of droplet refraction. Then, the characteristics of scattering attenuation in fog days were identified under different levels of visibility. The Rayleigh approximation method was used to numerically model the scattering effect of small droplets and the effect of temperature and visibility on characteristic attenuation. Results show that, by comparing the distribution of different raindrop sizes, the Joss distribution was found to be quite accurate. Raindrop size distribution and scattering attenuation characteristics under different rainfall rates were identified using the Mie scattering method. The meteorological environment is complex in the near-earth atmosphere and the scattering attenuation of terahertz waves under fog, hazy, and rainy conditions cannot be ignored. Meteorological factors, such as visibility and rainfall rate, exert critical influences on the scattering attenuation characteristics of terahertz waves.

Experimental study and numerical simulation Concerning fogging characteristics and Improvement of return air utilization for electric vehicles

Anti-fogging treatment is a key task associated with the thermal management of electric vehicles, which focuses on utilizing the cabin return air to reduce heating load and save battery power. The present study analyzes the interior climate characteristics of the vehicle with an improved thermal and humidity model (T&H model), which considers a thin air layer between the windshield and the interior air so as to enhance the accuracy of the model. A test bench is constructed to investigate the fogging characteristics of the windshield under various environmental conditions, based on which two relevant factors are experimentally measured, i.e., the difference between the critical moisture content (CMC) of the surface air layer and the corresponding saturation moisture content (SMC) associated with the windshield surface temperature, as well as the impact of air velocity on the convective heat transfer coefficient. The results obtained here are leveraged to improve the T&H model, which is in turn validated with an additional experimental test, showing errors below 10%. Finally, numerical simulation is conducted to analyze the maximum return air ratio, which shows that with an elevated driving speed, an increased convective heat transfer coefficient leads to a subdued windshield temperature, which in turn causes the return air ratio to drop. This driving-speed-dependency of return air ratio becomes more pronounced as the relative humidity of exterior air increases.

Winter Fog Experiment Over the Indo-Gangetic Plains of India

The objectives of the Winter Fog Experiment (WIFEX) over the Indo-Gangetic Plains of India are to develop better now-casting and forecasting of winter fog on various time-and spatial scales. Maximum fog occurrence over northwest India is about 48 days (visibility <1000 m) per year, and it occurs mostly during the December-February time-period. The physical and chemical characteristics of fog, meteorological factors responsible for its genesis, sustenance, intensity and dissipation are poorly understood. Improved understanding on the above aspects is required to develop reliable forecasting models and observational techniques for accurate prediction of the fog events. Extensive sets of comprehensive ground-based instrumentation were deployed at the Indira Gandhi International Airport, New Delhi. Major in situ sensors were deployed to measure surface micrometeorological conditions, radiation balance, turbulence, thermodynamical structure of the surface layer, fog droplet and aerosol microphysics, aerosol optical properties, and aerosol and fog water chemistry to describe the complete environmental conditions under which fog develops. In addition, Weather Forecasting Model coupled with chemistry is planned for fog prediction at a spatial resolution of 2 km. The present study provides an introductory overview of the winter fog field campaign with its unique instrumentation.

A non-cooperative differential game-based security model in fog computing

Fog computing is a new paradigm providing network services such as computing, storage between the end users and cloud. The distributed and open structure are the characteristics of fog computing, which make it vulnerable and very weak to security threats. In this article, the interaction between vulnerable nodes and malicious nodes in the fog computing is investigated as a non-cooperative differential game. The complex decision making process is reviewed and analyzed. To solve the game, a fictitious play-based algorithm is which the vulnerable node and the malicious nodes reach a feedback Nash equilibrium. We attain optimal strategy of energy consumption with QoS guarantee for the system, which are conveniently operated and suitable for fog nodes. The system simulation identifies the propagation of malicious nodes. We also determine the effects of various parameters on the optimal strategy. The simulation results support a theoretical foundation to limit malicious nodes in fog computing, which can help fog service providers make the optimal dynamic strategies when different types of nodes dynamically change their strategies.

Security and Privacy in Fog Computing: Challenges

Fog computing paradigm extends the storage, networking, and computing facilities of the cloud computing toward the edge of the networks while offloading the cloud data centers and reducing service latency to the end users. However, the characteristics of fog computing arise new security and privacy challenges. The existing security and privacy measurements for cloud computing cannot be directly applied to the fog computing due to its features, such as mobility, heterogeneity, and large-scale geo-distribution. This paper provides an overview of existing security and privacy concerns, particularly for the fog computing. Afterward, this survey highlights ongoing research effort, open challenges, and research trends in privacy and security issues for fog computing.

Climatic Characteristics of Fog in Tbilisi Airport

Climatic Characteristics of Fog in Tbilisi Airport

Research on Fog-and-Haze Purification Technology for Highways

AbstractA fog-and-haze purification technology for highways is proposed by analyzing the causes and characteristics of fog and haze and by combining the ground and underground facilities on the hig...

The Effect of Freezing Drizzle, Sleet and Snow on Microphysical Characteristics of Supercooled Fog during the Icing Process in a Mountainous Area

Both the similar and different effects of freezing drizzle, sleet and snow on microphysical properties of supercooled fog were analyzed for fourteen events during a comprehensive wire icing, fog, and precipitation observation experiment conducted at Enshi radar station (30°17′N, 109°16′E; 1722 m a.s.l.) on a hilltop in Shibanling, Hubei, China. Liquid precipitation is in a relatively stable form in mountainous areas. Short-term precipitation (1–3 h) is dominant with temperature below 0 °C. The wet scavenging effect of freezing drizzle on small fog droplets with a size range less than 6–12 μm is weak but is stronger for fog droplets with a larger size, which is opposite to the effects of solid precipitation, broadening the fog droplet spectra significantly. As the fog droplet diameter increases, the distributions of droplet spectra change from leptokurtosis to platykurtosis and from positive skewness to negative skewness. Occurrence of freezing drizzle would improve the positive correlation of N-r in dissipation and oscillation periods, resulting in the N-r relationship having a weak negative correlation in the maturity period, and resulting in the transition of the N-L and N-r relationships into positive correlations in the development period. Meanwhile, the emergence of solid precipitation particles would result in negative values for the correlation coefficients of N-L and N-r. The change in relationships among the microphysical properties was caused by the occurrence of different phase precipitation, showing the influence on the main microphysical mechanisms of supercooled fog.

Changes in marine fog in a warmer climate

AbstractChanges in marine fog in a warmer climate are investigated through simulations using the atmospheric component of a global climate model, with both observed and perturbed sea surface temperature forcing. Global changes in marine fog occurrence in different seasons are compared. We show that the changes in marine fog occurrence correspond well to changes in horizontal temperature advection near the surface in a warmer climate. Therefore, the changes in marine fog can be well explained by large‐scale circulation changes. Regarding changes in the characteristics of marine fog, we show that the in‐cloud liquid water content of marine fog is consistently increased in a warmer climate, for a given horizontal surface temperature advection. It is also confirmed that the contribution of changes in marine fog to cloud feedback is not negligible, but is small.

Local Meteorological and Large-Scale Weather Characteristics of Fog over the Grand Casablanca Region, Morocco

AbstractUsing a fog event approach, the local meteorological and synoptic characteristics of fogs that formed over the Grand Casablanca (GCB) region during a 9-yr period (2001–09) are investigated. A climatological study of fog, with emphasis on the fog temporal variability and spatial distribution, is carried out on the basis of hourly surface meteorological observations at two synoptic stations in the region. The fog events are classified into fog types, using an objective classification algorithm, and are characterized by their duration, intensity, and times of onset and dissipation. In addition, fog events are classified into two distinct categories (isolated and widespread) on the basis of their spatial extent. K-means cluster analysis is applied to the patterns of mean sea level pressure in ERA-Interim reanalyses at 0000 UTC to determine the synoptic circulation types associated with fog occurrence in the GCB region. Results show that the fog frequency at the inland suburban station is more recurrent than at the coastal urban station. The fog events are predominantly of the advection–radiation type, with a marked tendency of nighttime occurrence during the winter. The spatial distribution analysis points out the localized character of fog and reveals the possibility of different fog types occurring when fog is present near the two stations simultaneously. Furthermore, the interaction between local- and large-scale mechanisms suggests that advective processes associated with sea-breeze circulation during daytime, followed by radiative processes early in the night, often lead to fog formation over the GCB region.

Highly transparent superhydrophilic graphene oxide coating for antifogging

The superhydrophilic property of the surface allows water to spread completely across the surface rather than remain as droplets, thus making the surface antifogging. In this work, graphene oxide was prepared by the modified Hummers method, and the superhydrophilic and highly transparent functional graphene oxide coating had been fabricated on the glass substrate through a spin coating process. The as-prepared coated glass had a static water contact angle of 3.7° and a relatively high transmittance reaching about 76% throughout the visible region. For comparison, we studied the antifogging properties of the graphene oxide coated glass and the bare glass surfaces. The result shows these glass exhibits absolutely different fogging characteristics, and the graphene oxide coated glass has the superior antifogging property.

The Impacts of E-Commerce as a Service upon Fog Computing

Fog Computing is a technology that extends cloud computing and services to the edge of the network. It provides data, compute, storage and application services to the users like cloud. From kitchen equipment to aeroplane, started getting an IP address which has also been a part of internet. In the past few years, the great transmission of theoretical concept of different industries such as E-commerce into real application has been used by cloud computing. Based on adopted fog features and characteristics those are encouraging small companies that providing their E-commerce products to adopt their development into fog computing. In order to assist the E-commerce small companies with the right way to start with the basic requirements and upgrading their computing resources as their fog user base grows with time, herewith the impacts of Ecommerce as the services upon fog computing is proposed.

Fog computing for vehicular Ad-hoc networks: paradigms, scenarios, and issues

Vehicular Ad-hoc networks (VANETs) are kinds of mobile Ad-hoc networks (MANETs), which consist of mobile vehicles with on-board units (OBUs) and roadside units (RSUs). With the rapid development of computation and communication technologies, peripheral or incremental changes in VANETs evolve into a revolution in process. Cloud computing as a solution has been deployed to satisfy vehicles in VANETs which are expected to require resources (such as computing, storage and networking). Recently, with special requirements of mobility, location awareness, and low latency, there has been growing interest in research into the role of fog computing in VANETs. The merging of fog computing with VANETs opens an area of possibilities for applications and services on the edge of the cloud computing. Fog computing deploys highly virtualized computing and communication facilities at the proximity of mobile vehicles in VANET. Mobile vehicles in VANET can also demand services of low-latency and short-distance local connections via fog computing. This paper presents the current state of the research and future perspectives of fog computing in VANETs. Moreover, we discuss the characteristics of fog computing and services based on fog computing platform provided for VANETs. In this paper, some opportunities for challenges and issues are mentioned, related techniques that need to be considered have been discussed in the context of fog computing in VANETs. Finally, we discuss about research directions of potential future work for fog computing in VANETs. Within this article, readers can have a more thorough understanding of fog computing for VANETs and the trends in this domain.

Characteristics of fog in an aerodrome in a tropical lowland area in northwestern Amazonia

An analysis of meteorological terminal aviation routine weather reports (METAR) generated at the “Ernesto Esguerra Cubides” (EEC) aerodrome (Tres Esquinas Airbase) is shown. The aerodrome is located in the municipality of Solano in the Colombian Amazonia. Reports covering the period January 1, 2009 to December 31, 2012 helped to identify and analyze the characteristics of the occurrence of fog events at the EEC aerodrome. The results show that fog is a frequent meteorological phenomenon at the EEC aerodrome: on average, one in five days of the study period had at least one report of fog. At the EEC, fog is the meteorological phenomenon that causes the most weather-related aerodrome closures; it caused 45.26% of the closures of the EEC aerodrome. The high percentage of episodes of fog with calm wind (95%) and its high occurrence between 22:00 and 08:00 LT suggest that fog at the EEC aerodrome is basically radiative-type. Fog appears in every month of the year. In addition, three episodes of dense fog over the EEC aerodrome were analyzed from METAR and aviation special weather reports (SPECI), images from the GOES-13 satellite, NOAA surface analysis charts and radio soundings made at the EEC aerodrome. The analysis of this information allowed us to establish the weather conditions in which three fog events were presented. It was found that in times when the North Atlantic anticyclone is farthest from the Colombian territory and the Intertropical Convergence Zone is located north of the territory, subsidence is generated in the lower and middle levels by inhibiting convection over the northwestern part of the Colombian Amazonia and favoring the occurrence of fog or mist in the area. Subsidence over the area is also related to convective activity in the departments of Guainía, Vaupés and Guaviare. This, together with sky conditions with few clouds and calm winds favor radiative cooling, increasing the likelihood of fog and mist.

Impacts of Fog Characteristics, Forward Illumination, and Warning Beacon Intensity Distribution on Roadway Hazard Visibility.

Warning beacons are critical for the safety of transportation, construction, and utility workers. These devices need to produce sufficient luminous intensity to be visible without creating glare to drivers. Published standards for the photometric performance of warning beacons do not address their performance in conditions of reduced visibility such as fog. Under such conditions light emitted in directions other than toward approaching drivers can create scattered light that makes workers and other hazards less visible. Simulations of visibility of hazards under varying conditions of fog density, forward vehicle lighting, warning beacon luminous intensity, and intensity distribution were performed to assess their impacts on visual performance by drivers. Each of these factors can influence the ability of drivers to detect and identify workers and hazards along the roadway in work zones. Based on the results, it would be reasonable to specify maximum limits on the luminous intensity of warning beacons in directions that are unlikely to be seen by drivers along the roadway, limits which are not included in published performance specifications.

Single image haze removal based on haze physical characteristics and adaptive sky region detection

Outdoor images are often degraded by haze and other inclement weather conditions, which affect both consumer photographs and computer vision applications severely. Therefore, researchers have proposed plenty of restoration approaches to deal with this problem. However, it is hard to tackle the color distortion problem in restored images with ignoring the differences between fog and haze. Meanwhile, the atmospheric light is also an important variable that influences the global illumination of images. In this paper, we analyze the physical meaning of atmospheric light first, and estimate atmospheric light by a novel method of obtaining the sky region in images, which is based on our newly proposed sky region prior. Then after exploring physical characteristics of fog and haze, we explain why images taken in haze appear yellowish, and eliminate this phenomenon by our adaptive channel equalization method. Quantitative comparisons with seven state-of-art algorithms on a variety of real-world haze images demonstrate that our algorithm can remove haze effectively and keep color fidelity better.