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Anomalous Propagation
Anomalous propagation (sometimes shortened to anaprop or anoprop) Peter Meischner (ed.), ''Weather Radar: Principles and Advanced Applications'', Springer Science & Business Media, 2005, page 144 includes different forms of radio propagation due to an unusual distribution of temperature and humidity with height in the atmosphere. While this includes propagation with larger losses than in a standard atmosphere, in practical applications it is most often meant to refer to cases when signal propagates beyond normal radio horizon. Anomalous propagation can cause interference to VHF and UHF radio communications if distant stations are using the same frequency as local services. Over-the-air analog television broadcasting, for example, may be disrupted by distant stations on the same channel, or experience distortion of transmitted signals ghosting). Radar systems may produce inaccurate ranges or bearings to distant targets if the radar "beam" is bent by propagation effects. However, ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weather Radar
A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation (meteorology), precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the intensity of the precipitation. Both types of data can be analyzed to determine the structure of storms and their potential to cause severe weather. During Radar in World War II, World War II, radar operators discovered that weather was causing echoes on their screens, masking potential enemy targets. Techniques were developed to filter them, but scientists began to study the phenomenon. Soon after the war, military surplus, surplus radars were used to detect precipitation. Since then, weather radar has evolved and is used by national weather services, research departments in universities, and in television stations' weather d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Propagation
Radio propagation is the behavior of radio waves as they travel, or are wave propagation, propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection (physics), reflection, refraction, diffraction, absorption (electromagnetic radiation), absorption, polarization (waves), polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave Broadcasting, broadcasters, to designing reliable Mobile phone, mobile telephone systems, to radio navigation, to operation of radar systems. Several different types of propagation are used in practical radio transmission systems. ''Line-of-sight propagation'' means radio waves which travel in a straight line from the transmitting antenna to the receiving ante ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environment Canada
Environment and Climate Change Canada (ECCC; )Environment and Climate Change Canada is the applied title under the Federal Identity Program; the legal title is Department of the Environment (). is the Ministry (government department), department of the Government of Canada responsible for coordinating environmental policies and programs, as well as preserving and enhancing the natural environment and renewable resources. It is also colloquially known by its former name, Environment Canada (EC; ). The Minister of Environment and Climate Change, minister of environment and climate change has been Julie Dabrusin since May 13, 2025; Environment and Climate Change Canada supports the minister's mandate to: "preserve and enhance the quality of the natural environment, including water, air, soil, flora and fauna; conserve Canada's renewable resources; conserve and protect Canada's water resources; forecast daily weather conditions and warnings, and provide detailed meteorological inform ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-line-of-sight Propagation
Non-line-of-sight (NLOS) radio propagation occurs outside of the typical line-of-sight (LOS) between the transmitter and receiver, such as in ground reflections. Near-line-of-sight (also NLOS) conditions refer to partial obstruction by a physical object present in the innermost Fresnel zone. Obstacles that commonly cause NLOS propagation include buildings, trees, hills, mountains, and, in some cases, high voltage electric power lines. Some of these obstructions reflect certain radio frequencies, while some simply absorb or garble the signals; but, in either case, they limit the use of many types of radio transmissions, especially when low on power budget. Lower power levels at a receiver reduce the chance of successfully receiving a transmission. Low levels can be caused by at least three basic reasons: low transmit level, for example Wi-Fi power levels; far-away transmitter, such as 3G more than away or TV more than away; and obstruction between the transmitter and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Weather Service
The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the purposes of protection, safety, and general information. It is a part of the National Oceanic and Atmospheric Administration (NOAA) branch of the United States Department of Commerce, Department of Commerce, and is headquartered in Silver Spring, Maryland, within the Washington metropolitan area. The agency was known as the United States Weather Bureau from 1891 until it adopted its current name in 1970. The NWS performs its primary task through a collection of national and regional centers, and 122 local List of National Weather Service Weather Forecast Offices, Weather Forecast Offices (WFOs). As the NWS is an agency of the U.S. federal government, most of its products are in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artifact (error)
In natural science and signal processing, an artifact or artefact is any error in the perception or representation of any information introduced by the involved equipment or technique(s). Statistics In ''statistics'', statistical artifacts are apparent effects that are introduced inadvertently by methods of data analysis rather than by the process being studied. Computer science In ''computer science'', digital artifacts are anomalies introduced into digital signals as a result of digital signal processing. Microscopy In ''microscopy'', visual artifacts are sometimes introduced during the processing of samples into slide form. Econometrics In ''econometrics'', which focuses on computing relationships between related variables, an artifact is a spurious finding, such as one based on either a faulty choice of variables or an over-extension of the computed relationship. Such an artifact may be called a ''statistical artifact''. For instance, imagine a hypothetical finding ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse-Doppler Radar
A pulse-Doppler radar is a radar system that determines the range to a target using pulse-timing techniques, and uses the Doppler effect of the returned signal to determine the target object's velocity. It combines the features of pulse radars and continuous-wave radars, which were formerly separate due to the complexity of the electronics. The first operational pulse-Doppler radar was in the CIM-10 Bomarc, an American long range supersonic missile powered by ramjet engines, and which was armed with a W40 nuclear weapon to destroy entire formations of attacking enemy aircraft. Pulse-Doppler systems were first widely used on fighter aircraft starting in the 1960s. Earlier radars had used pulse-timing in order to determine range and the angle of the antenna (or similar means) to determine the bearing. However, this only worked when the radar antenna was not pointed down; in that case the reflection off the ground overwhelmed any returns from other objects. As the ground moves at th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doppler Radar
A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance. It does this by bouncing a microwave signal off a desired target and analyzing how the object's motion has altered the frequency of the returned signal. This variation gives direct and highly accurate measurements of the radial component of a target's velocity relative to the radar. The term applies to radar systems in many domains like aviation, police radar detectors, navigation, meteorology, etc. Concept Doppler effect The Doppler effect (or Doppler shift), named after Austrian physicist Christian Doppler who proposed it in 1842, is the difference between the observed frequency and the emitted frequency of a wave for an observer moving relative to the source of the waves. It is commonly heard when a vehicle sounding a siren approaches, passes and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Eruption
A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three main types of volcanic eruptions. Magmatic eruptions involve the decompression of gas within magma that propels it forward. Phreatic eruptions are driven by the superheating of steam due to the close proximity of magma. This type exhibits no magmatic release, instead causing the granulation of existing rock. Phreatomagmatic eruptions are driven by the direct interaction of magma and water, as opposed to phreatic eruptions, where no fresh magma reaches the surface. Within these broad eruptive types are several subtypes. The we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sand Storm
A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a Outflow boundary, gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transported by Saltation (geology), saltation and suspension, a process that moves soil from one place and Deposition (sediment), deposits it in another. These storms can reduce visibility, disrupt transportation, and pose serious health risks. Over time, repeated dust storms can reduce agricultural productivity and contribute to desertification. The arid regions of North Africa, the Middle East, Central Asia and China are the main terrestrial sources of airborne dust. It has been argued that poor management of Earth, Earth's drylands, such as neglecting the fallow system, are increasing the size and frequency of dust storms from desert margins and changing both the local and global climate, as well as impacting local economies. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaff (radar Countermeasure)
Chaff, originally called Window or Düppel, is a Radar jamming and deception, radar countermeasure involving the dispersal of thin strips of aluminium, Metallizing, metallized glass fiber, or Metallised film, plastic. Dispersed chaff produces a large radar cross section intended to blind or disrupt radar systems. Modern military forces use chaff to distract Active radar homing, active radar homing missiles from their targets. Military aircraft and warships can be equipped with chaff dispensing systems for self-defense. During its Ballistic missile flight phases#Midcourse, midcourse phase, an intercontinental ballistic missile may release chaff along with its other Penetration aid, penetration aids. Contemporary radar systems can distinguish chaff from legitimate targets by measuring the Doppler shift, Doppler effect; chaff quickly loses speed after leaving an aircraft, and the resulting shift in wavelength of the radar return can be measured. To counter this, a chaff cloud can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clutter (radar)
Clutter is the unwanted return (echoes) in electronic systems, particularly in reference to radars. Such echoes are typically returned from ground, sea, rain, animals/insects, chaff and atmospheric turbulences, and can cause serious performance issues with radar systems. What one person considers to be unwanted clutter, another may consider to be a wanted target. However, targets usually refer to point scatterers and clutter to extended scatterers (covering many range, angle, and Doppler cells). The clutter may fill a volume (such as rain) or be confined to a surface (like land). A knowledge of the volume or surface area illuminated is required to estimated the echo per unit volume, η, or echo per unit surface area, σ° (the radar backscatter coefficient). Causes Clutter may be caused by man-made objects such as buildings and — intentionally — by radar countermeasures such as chaff. Other causes include natural objects such as terrain features, sea, precipitation, hail ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
