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Topic Review
Flood Prediction Using ML Models
Floods are among the most destructive natural disasters, which are highly complex to model. The research on the advancement of flood prediction models contributed to risk reduction, policy suggestion, minimization of the loss of human life, and reduction of the property damage associated with floods. To mimic the complex mathematical expressions of physical processes of floods, during the past two decades, machine learning (ML) methods contributed highly in the advancement of prediction systems providing better performance and cost-effective solutions. Due to the vast benefits and potential of ML, its popularity dramatically increased among hydrologists.Researchers through introducing novel ML methods and hybridizing of the existing ones aim at discovering more accurate and efficient prediction models. The main contribution of this paper is to demonstrate the state of the art of ML models in flood prediction and to give insight into the most suitable models. In this paper, the literature where ML models were benchmarked through a qualitative analysis of robustness, accuracy, effectiveness, and speed are particularly investigated to provide an extensive overview on the various ML algorithms used in the field. The performance comparison of ML models presents an in-depth understanding of the different techniques within the framework of a comprehensive evaluation and discussion. As a result, this paper introduces the most promising prediction methods for both long-term and short-term floods. Furthermore, the major trends in improving the quality of flood prediction models are investigated. Among them, hybridization, data decomposition, algorithm ensemble, and model optimization are reported as the most effective strategies for the improvement of ML methods. This survey can be used as a guideline for hydrologists as well as climate scientists in choosing the proper ML method according to the prediction task.
  • 12.1K
  • 04 Jan 2023
Topic Review
Physical and Chemical Aspects of Fog Water
Fog water have been rapidly increasing due to its negative impacts on different environmental processes. However, fog water harvesting has become beneficial in various countries to overcome water scarcity. Accurate fog forecasting remains a challenging issue due to its spatio-temporal variability and uncertainties despite the development and efforts made to understand its chemistry and microphysics. The literature proved that the decrease in fog frequency over time in most countries is mainly attributed to the improvement in air quality or the change in regional climatic conditions. 
  • 10.1K
  • 05 Jan 2024
Topic Review
Relative Humidity
Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is the dew point.
  • 5.0K
  • 29 Sep 2022
Topic Review
Atmospheric Correction for Landsat 8
Ocean colour (OC) remote sensing is important for monitoring marine ecosystems. However, inverting the OC signal from the top-of-atmosphere (TOA) radiance measured by satellite sensors remains a challenge as the retrieval accuracy is highly dependent on the performance of the atmospheric correction as well as sensor calibration. In this study, the performances of four atmospheric correction (AC) algorithms, the Atmospheric and Radiometric Correction of Satellite Imagery (ARCSI), Atmospheric Correction for OLI ‘lite’ (ACOLITE), Landsat 8 Surface Reflectance (LSR) Climate Data Record (Landsat CDR), herein referred to as LaSRC (Landsat 8 Surface Reflectance Code), and the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) Data Analysis System (SeaDAS), implemented for Landsat 8 Operational Land Imager (OLI) data, were evaluated. The OLI-derived remote sensing reflectance (Rrs) products (also known as Level-2 products) were tested against near-simultaneous in-situ data acquired from the OC component of the Aerosol Robotic Network (AERONET-OC). Analyses of the match-ups revealed that generic atmospheric correction methods (i.e., ARCSI and LaSRC), which perform reasonably well over land, provide inaccurate Level-2 products over coastal waters, in particular, in the blue bands. Between water-specific AC methods (i.e., SeaDAS and ACOLITE), SeaDAS was found to perform better over complex waters with root-mean-square error (RMSE) varying from 0.0013 to 0.0005 sr−1 for the 443 and 655 nm channels, respectively. An assessment of the effects of dominant environmental variables revealed AC retrieval errors were influenced by the solar zenith angle and wind speed for ACOLITE and SeaDAS in the 443 and 482 nm channels. Recognizing that the AERONET-OC sites are not representative of inland waters, extensive research and analyses are required to further evaluate the performance of various AC methods for high-resolution imagers like Landsat 8 and Sentinel-2 under a broad range of aquatic/atmospheric conditions.
  • 3.6K
  • 30 Oct 2020
Topic Review
High Frequency Active Auroral Research Program
The High Frequency Active Auroral Research Program (HAARP) was initiated as an ionospheric research program jointly funded by the United States Air Force , the U.S. Navy, the University of Alaska Fairbanks, and the Defense Advanced Research Projects Agency (DARPA). It was designed and built by BAE Advanced Technologies (BAEAT). Its original purpose was to analyze the ionosphere and investigate the potential for developing ionospheric enhancement technology for radio communications and surveillance. As a university-owned facility, HAARP is a high-power, high-frequency transmitter used for study of the ionosphere. The most prominent instrument at HAARP is the Ionospheric Research Instrument (IRI), a high-power radio frequency transmitter facility operating in the high frequency (HF) band. The IRI is used to temporarily excite a limited area of the ionosphere. Other instruments, such as a VHF and a UHF radar, a fluxgate magnetometer, a digisonde (an ionospheric sounding device), and an induction magnetometer, are used to study the physical processes that occur in the excited region. Work on the HAARP facility began in 1993. The current working IRI was completed in 2007; its prime contractor was BAE Systems Advanced Technologies. As of 2008, HAARP had incurred around $250 million in tax-funded construction and operating costs. In May 2014, it was announced that the HAARP program would be permanently shut down later in the year. After discussions between the parties, ownership of the facility and its equipment was transferred to the University of Alaska Fairbanks in August 2015. HAARP is a target of conspiracy theorists, who claim that it is capable of "weaponizing" weather. Commentators and scientists say that advocates of this theory are uninformed, as claims made fall well outside the abilities of the facility, if not the scope of natural science.
  • 2.7K
  • 21 Nov 2022
Topic Review
Trough (Meteorology)
A trough is an elongated region of relatively low atmospheric pressure without a closed isobaric contour that would define it as a low pressure area. Since low pressure implies a low height on a pressure surface, troughs and ridges refer to features in an identical sense as those on a topographic map. Troughs may be at the surface, or aloft. Near-surface troughs sometimes mark a weather front associated with clouds, showers, and a wind direction shift. Upper-level troughs in the jet stream (as shown in diagram) reflect cyclonic filaments of vorticity. Their motion induces upper-level wind divergence, lifting and cooling the air ahead (downstream) of the trough and helping to produce cloudy and rain conditions there. Unlike fronts, there is not a universal symbol for a trough on a surface weather analysis chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked as a dashed line or bold line. In the UK, Hong Kong and Fiji, it is represented by a bold line extended from a low pressure center or between two low pressure centers; in Macau and Australia, it is a dashed line. If they are not marked, troughs may still be identified as an extension of isobars away from a low pressure center.
  • 2.6K
  • 14 Oct 2022
Topic Review
Tropospheric Ozone
Ozone (O3) is a trace gas of the troposphere, with an average concentration of 20–30 parts per billion by volume (ppbv), with close to 100 ppbv in polluted areas. Ozone is also an important constituent of the stratosphere, where the ozone layer exists which is located between 10 and 50 kilometers above the earths surface. The troposphere is the lowest layer of the Earth's atmosphere. It extends from the ground up to a variable height of approximately 14 kilometers above sea level. Ozone is least concentrated in the ground layer (or planetary boundary layer) of the troposphere. Ground level or tropospheric ozone is created by chemical reactions between oxides of nitrogen (NOx gases) and volatile organic compounds (VOCs). The combination of these chemicals in the presence of sunlight form ozone. Its concentration increases as height above sea level increases, with a maximum concentration at the tropopause. About 90% of total ozone in the atmosphere is in the stratosphere, and 10% is in the troposphere. Although tropospheric ozone is less concentrated than stratospheric ozone, it is of concern because of its health effects. Ozone in the troposphere is considered a greenhouse gas, and may contribute to global warming. Photochemical and chemical reactions involving ozone drive many of the chemical processes that occur in the troposphere by day and by night. At abnormally high concentrations (the largest source being emissions from combustion of fossil fuels), it is a pollutant, and a constituent of smog. Its levels have increased significantly since the industrial revolution, as NOx gasses & VOCs are some of the byproducts of combustion. With more heat and sunlight in the summer months, more ozone is formed which is why regions often experience higher levels of pollution in the summer months. Although the same molecule, ground level ozone can be harmful to our health, unlike stratospheric ozone that protects the earth from excess UV radiation. Photolysis of ozone occurs at wavelengths below approximately 310–320 nanometres. This reaction initiates the chain of chemical reactions that remove carbon monoxide, methane, and other hydrocarbons from the atmosphere via oxidation. Therefore, the concentration of tropospheric ozone affects how long these compounds remain in the air. If the oxidation of carbon monoxide or methane occur in the presence of nitrogen monoxide (NO), this chain of reactions has a net product of ozone added to the system.
  • 2.5K
  • 24 Nov 2022
Topic Review
Theory of Urban Farming
Urban agriculture attempts to advance sustainable agricultural methods, such as composting, the use of organic fertilizers, and water conservation. It involves a multidisciplinary approach, combining knowledge of soil science, plant physiology, sustainable agriculture, and technology. Crop rotation and companion planting are two other methods urban farmers can utilize to lessen the demand for pesticides and herbicides. The crops are managed using advanced technology involving sensor-based monitoring, automated irrigation systems, and data analysis to maximize crop output. Urban crop farming is regarded as an important agricultural activity for the modern and circular economy, as it can also improve the urban residents’ income and reduce agricultural waste and gaseous emissions from long-distance transportation.
  • 2.1K
  • 23 May 2023
Topic Review Video
Global Solar Radiation
An empirical model of global solar irradiance (EMGSI) under all sky conditions was developed by using solar radiation and meteorological parameters at Sodankylä. The calculated hourly global solar irradiance is in agreement with that observed at the ground during 2008–2011 and at the top of the atmosphere (TOA). Using this empirical model, the albedos at the TOA and the surface were calculated, and they are in agreement with the satellite-retrieved values. 
  • 1.9K
  • 25 Nov 2021
Topic Review
Pollutant Dispersion
This entry reviews atmospheric processes affecting pollutant transport and diffusion over complex terrain, focusing in particular on the peculiarities of processes over mountains when compared to flat terrain. In fact, pollutant dispersion processes over complex terrain are much more complicated than over flat areas, as they are affected by atmospheric interactions with the orography at different spatial scales. In particular, atmospheric flows over complex terrain are characterized by a continuous and interacting range of scales, from synoptic forcing to mesoscale circulations and turbulence fluctuations. In complex terrain, the mechanical and thermal influence of the orography can modify the large-scale flow and produce smaller-scale motions which would not exist on flat terrain, thus enhancing the spatial and temporal variability of atmospheric processes relevant for pollutant dispersion.
  • 1.9K
  • 26 Oct 2020
Topic Review
UAVs to CBRN Threats monitoring
Unmanned aerial vehicles (UAVs) play an increasingly important role in various areas of life, including in terms of protection and security. The possibilities of using the devices were analyzed in terms of weather conditions, construction, and used materials in CBRN (chemical, biological, radiological, nuclear) threat situations. It was found that, thanks to the use of appropriate sensors, cameras, and software of UAVs integrated with a given system, it is possible to obtain information on air quality at a given moment, which is very important for the safety of people and the environment. However, several elements, including the possibility of use in acidification conditions, requires refinement to changing crisis conditions.
  • 1.7K
  • 28 Dec 2020
Topic Review
Indoor Air Quality Management
The existence of indoor air pollutants—such as ozone, carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen dioxide, particulate matter, and total volatile organic compounds—is evidently a critical issue for human health. Over the past decade, various international agencies have continually refined and updated the quantitative air quality guidelines and standards in order to meet the requirements for indoor air quality management. This entry first provides a systematic review of the existing air quality guidelines and standards implemented by different agencies, which include the Ambient Air Quality Standards (NAAQS); the World Health Organization (WHO); the Occupational Safety and Health Administration (OSHA); the American Conference of Governmental Industrial Hygienists (ACGIH); the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); the National Institute for Occupational Safety and Health (NIOSH); and the California ambient air quality standards (CAAQS). It then adds to this by providing a state-of-art review of the existing low-cost air quality sensor (LCAQS) technologies, and analyzes the corresponding specifications, such as the typical detection range, measurement tolerance or repeatability, data resolution, response time, supply current, and market price. Finally, it briefly reviews a sequence (array) of field measurement studies, which focuses on the technical measurement characteristics and their data analysis approaches.
  • 1.7K
  • 18 Jan 2021
Topic Review
Rainfall Threshold
Sediment-related disaster is one of the most significant natural disasters, from the perspective of magnitude, damage and loss to human life and infrastructure, and disruption to socio-economic activities. The rainfall threshold is the condition or amount of rainfall that is likely to initiate sediment-related disasters, it is agreed that the rainfall threshold is the most significant tool to predict impending occurrences.
  • 1.7K
  • 26 Oct 2022
Topic Review
Atmospheric Influence on Grapevine Development
In many European regions, viticulture and winemaking play a major socioeconomic role in local economies, with climate being a central component of the terroirs, governing vineyard microclimate, vine development and growth, phenology, yield, and grape berry composition, which ultimately control attributes and typicity of the produced wines. Nonetheless, climate change is already affecting the viticultural suitability of many wine regions throughout the continent and is expected to continue along this same path in the upcoming decades. These climate-driven shifts may lead to a redesign of the geographical distribution of wine regions, while wine typicity may also be threatened in most cases. Climate change does require the implementation of well-timed, appropriate, and economically efficient adaptation strategies, while respecting local specificities for an effective reduction of the risks to which this vulnerable sector is exposed. However, knowledge on the adaptation potential of a range of measures is still incipient and will need more research in the near future.
  • 1.5K
  • 28 Oct 2020
Topic Review
Viable Bacteria in Dust-Generating Area
The distribution of microorganisms in the atmospheric circulation affects the animals that inhabit the area. Also, many organisms that share the environment also influence the distribution of environmental bacteria. In this paper, we focused on microbes that survive on the surface of Asian Dust, and clarified their topographical features and distribution. The characteristics of microorganisms that are easily influenced by environmental factors, and their effects on the atmospheric circulation are considered as issues of the One Health Concept.
  • 1.5K
  • 16 Sep 2020
Topic Review
Vegetation Dynamics and Climate Change
Climate extremes and their impacts on vegetation dynamics have been of great concern to the ecosystem and environmental conservation and the policy-decision makers. Of great concern now is that climate change impacts on vegetation dynamics have influenced the global terrestrial ecosystem adversely, thus making ecosystems vulnerability one of the current issues in ecological studies. For instance, the negative consequences attributed to natural hazards associated with climate extremes have been estimated to be billions of dollars across the globe. Accordingly, vegetation dynamics are influenced by several factors including climate change, environmental and climatic components among others. These can expend considerable impact on the water balance by evapotranspiration, interception and development strategy which has the potential to lead to vegetation degradation in a wide variety of ecosystems and biodiversity.
  • 1.5K
  • 30 Sep 2021
Topic Review Video
Chaos and Order in the Atmosphere
The Lorenz 1963 and 1969 models have been applied for revealing the chaotic nature of weather and climate and for estimating the atmospheric predictability limit. Recently, an in-depth analysis of classical Lorenz models (LMs) and newly developed, generalized Lorenz models suggested a revised view that “The atmosphere possesses chaos and order; it includes, as examples, emerging organized systems (such as tornadoes) and time varying forcing from recurrent seasons”, in contrast to the conventional view of “weather is chaotic”. The revised view focuses on distinct predictability and time varying multistability. Distinct predictability suggests limited predictability for chaotic solutions and unlimited predictability (or up to their lifetime) for non-chaotic solutions. To support the revised view, multistability (for attractor coexistence) and monostability (for single-type solutions) are first illustrated using kayaking and skiing as an analogy. Additionally, this entry provides a list of non-chaotic weather systems and a short list of suggested future tasks.
  • 1.4K
  • 29 Nov 2022
Topic Review
Groundwater dynamics
Analytical solutions of groundwater dynamics in an elongated aquifer subjected to general time-dependent recharge are presented. The lateral boundaries are specified heads with the head variations governed by general time-dependent functions.  General recharge function was not considered in previous works of this kind. Both single and double-porosity aquifers are considered. The solution is obtained using Fourier sine and Laplace transformations, followed by an inverse Fourier-Laplace transform involving residue theorem and convolutional integral. For the unconfined single-porosity aquifer case, the exact time-domain solution is obtained using the residue theorem; for the unconfined double-porosity aquifer case, the time-domain head is calculated using the de Hoog inverse Laplace algorithm. The presented solution can be used to estimate the hydraulic parameters of 1) groundwater head variation of a river basin aquifer subjected to general lateral head variation and recharge; 2) groundwater head variation in a double-porosity elongated fractured anticline; 3) groundwater depletion of an elongated fractured anticline subjected to recharge due to rainfall or snowmelt to its adjacent alluvial aquifer.  In addition, the presented solution can be utilized to optimize the irrigation pattern in a cropland between two trench drains to control the groundwater mound.
  • 1.2K
  • 23 Dec 2020
Topic Review
NOx Emission Reduction and Recovery
Since its first confirmed case at the end of 2019, COVID-19 has become a global pandemic in three months with more than 1.4 million confirmed cases worldwide, as of early April 2020. Quantifying the changes of pollutant emissions due to COVID-19 and associated governmental control measures is crucial to understand its impacts on economy, air pollution, and society. We used the WRF-GC model and the tropospheric NO2 column observations retrieved by the TROPOMI instrument to derive the top-down NOx emission change estimation between the three periods: P1 (January 1st to January 22nd, 2020), P2 (January 23rd, Wuhan lockdown, to February 9th, 2020), and P3 (February 10th, back-to-work day, to March 12th, 2020). We found that NOx emissions in East China averaged during P2 decreased by 50% compared to those averaged during P1. The NOx emissions averaged during P3 increased by 26% compared to those during P2. Most provinces in East China gradually regained some of their NOx emissions after February 10, the official back-to-work day, but NOx emissions in most provinces have not yet to return to their previous levels in early January. NOx emissions in Wuhan, the first epicenter of COVID-19, had no sign of emission recovering by March 12. A few provinces, such as Zhejiang and Shanxi, have recovered fast, with their averaged NOx emissions during P3 almost back to pre-lockdown levels.
  • 1.2K
  • 29 Oct 2020
Biography
Roy Spencer
Roy Warren Spencer (born December 20, 1955)[1] is a meteorologist,[2] a principal research scientist at the University of Alabama in Huntsville, and the U.S. Science Team leader for the Advanced Microwave Scanning Radiometer (AMSR-E) on NASA's Aqua satellite.[3][4] He has served as senior scientist for climate studies at NASA's Marshall Space Flight Center.[3][4] He is known for his satellite-b
  • 1.2K
  • 06 Dec 2022
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