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Severe Thunderstorm
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in cumulonimbus clouds. They are usually accompanied by strong winds and often produce Heavy rain (meteorology), heavy rain and sometimes Thundersnow, snow, Ice pellets, sleet, or hail, but some thunderstorms can produce little or Dry thunderstorm, no precipitation at all. Thunderstorms may thunderstorm training, line up in a series or become a rainband, known as a squall line. Strong or #Severe thunderstorms, severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lightning Pritzerbe 01 (MK)
Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on the land, ground. Following the lightning, the regions become partially or wholly electrically neutralized. Lightning involves a near-instantaneous release of energy on a scale averaging between 200 megajoules and 7 gigajoules. The air around the lightning flash rapidly heats to temperatures of about . There is an emission of electromagnetic radiation across a wide range of wavelengths, some visible as a bright flash. Lightning also causes thunder, a sound from the shock wave which develops as heated gases in the vicinity of the discharge experience a sudden increase in pressure. The most common occurrence of a lightning event is known as a thunderstorm, though they can also commonly occur in other types of energetic weather systems, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squall Line
A squall line, or quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front (which often are accompanied by abrupt and gusty wind shifts). Linear thunderstorm structures often contain heavy precipitation, hail, frequent lightning, strong straight-line winds, and occasionally tornadoes or waterspouts. Particularly strong straight-line winds can occur where the linear structure forms into the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern (LEWP), where mesoscale low-pressure areas are present. Some bow echoes can grow to become derechos as they move swiftly across a large area. On the back edge of the rainband associated with mature squall lines, a wake low can be present, on very rare occasions associated with a heat burst. Theory Polar front theory was developed by Jacob Bjerknes, derived from a dense netwo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downburst
In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. It originates under deep, moist convective conditions like cumulus congestus or cumulonimbus. Capable of producing damaging winds, it may sometimes be confused with a tornado, where high-velocity winds circle a central area, and air moves inward and upward. These usually last for seconds to minutes. Downbursts are particularly strong downdrafts within thunderstorms (or deep, moist convection as sometimes downbursts emanate from cumulonimbus or even cumulus congestus clouds that are not producing lightning). Downbursts are most often created by an area of significantly precipitation-cooled air that, after reaching the surface ( subsiding), spreads out in all directions producing strong winds. Dry downbursts are associated with thunderstorms that ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-latitudes
The middle latitudes, also called the mid-latitudes (sometimes spelled midlatitudes) or moderate latitudes, are spatial regions on either hemisphere of Earth, located between the Tropic of Cancer (latitude ) and the Arctic Circle () in the northern hemisphere and between the Tropic of Capricorn (-) and the Antarctic Circle (-) in the southern hemisphere. They include Earth's subtropical and temperate zones, which lie between the two tropics and the polar circles. Weather fronts and extratropical cyclones are usually found in this area, as well as occasional tropical cyclones or subtropical cyclones, which have traveled from their areas of formation closer to the Equator. The prevailing winds in the middle latitudes are often very strong. These parts of the world also see a wide variety of fast-changing weather as cold air masses from the poles and warm air masses from the tropics constantly push up and down over them against each other, sometimes alternating within hours of eac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downdraft
In meteorology, an updraft (British English: ''up-draught'') is a small-scale current of rising air, often within a cloud. Overview Vertical drafts, known as updrafts or downdrafts, are localized regions of warm or cool air that move vertically. A mass of warm air will typically be less dense than the surrounding region, and so will rise until it reaches air that is either warmer or less dense than itself. The converse will occur for a mass of cool air, and is known as subsidence. This movement of large volumes of air, especially when regions of hot, wet air rise, can create large clouds, and is the central source of thunderstorms. Drafts can also be caused by low or high pressure regions. A low pressure region will attract air from the surrounding area, which will move towards the center and then rise, creating an updraft. A high pressure region will attract air from the surrounding area, which will move towards the center and sink, spawning a downdraft. Updrafts and downdrafts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dew Point
The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to produce a relative humidity of 100%. This temperature depends on the pressure and water content of the air. When the air at a temperature above the dewpoint is cooled, its moisture capacity is reduced and airborne water vapor will Condensation, condense to form liquid water known as dew. When this occurs through the air's contact with a colder surface, dew will form on that surface. The dew point is affected by the air's humidity. The more moisture the air contains, the higher its dew point. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed via deposition (phase transition), deposition rather than condensation. In liquids, the analog to the dew point is the cloud point. Humidity If all the other factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls; this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Condense
Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition. Condensation is usually associated with water. Initiation Condensation is initiated by the formation of atomic/molecular clusters of that species within its gaseous volume—like rain drop or snow flake formation within clouds—or at the contact between such gaseous phase and a liquid or solid surface. In clouds, this can be catalyzed by water-nucleating proteins, produced by atmospheric microbes, which are capable of binding gaseous or liquid water molecules. Reversibility scenarios A few distinct rever ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shortwave (meteorology)
A shortwave or shortwave trough is an embedded kink in the trough / ridge pattern. Its length scale is much smaller than that of and is embedded within longwaves, which are responsible for the largest scale (synoptic scale) weather systems. Shortwaves may be contained within or found ahead of longwaves and range from the mesoscale to the synoptic scale. Shortwaves are most frequently caused by either a cold pool or an upper level front. Shortwaves are commonly referred to as a vorticity maximum. Corresponding weather and effects Shortwaves are often associated with warm air advection (WAA) or cold air advection (CAA), which influence temperature. Due to the way they move the air around them and the way air moves away from them, shortwaves produce positive curvature vorticity and positive shear vorticity, respectively. Ahead of a shortwave there is large-scale lift due to divergence from positive vorticity advection (PVA). This lift often causes precipitation. In a capp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloud Forcing
Cloud feedback is a type of climate change feedback, where the overall cloud frequency, height, and the relative fraction of the different types of clouds are altered due to climate change, and these changes then affect the Earth's energy balance. On their own, clouds are already an important part of the climate system, as they consist of water vapor, which acts as a greenhouse gas and so contributes to warming; at the same time, they are bright and reflective of the Sun, which causes cooling. Clouds at low altitudes have a stronger cooling effect, and those at high altitudes have a stronger warming effect. Altogether, clouds make the Earth cooler than it would have been without them. If climate change causes low-level cloud cover to become more widespread, then these clouds will increase planetary albedo and contribute to cooling, making the overall cloud feedback ''negative'' (one that slows down the warming). But if clouds become higher and thinner due to climate change, then ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weather Front
A weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For instance, cold fronts can bring bands of thunderstorms and cumulonimbus precipitation or be preceded by squall lines, while warm fronts are usually preceded by stratiform precipitation and fog. In summer, subtler humidity gradients known as dry lines can trigger severe weather. Some fronts produce no precipitation and little cloudiness, although there is invariably a wind shift. Cold fronts generally move from west to east, whereas warm fronts move poleward, although any direction is possible. Occluded fronts are a hybrid merge of the two, and stationary fronts are stalled in their motion. Cold fronts and cold occlusions move faster than warm fronts and warm occlusions because the dense air behind them can lift as well as push the warme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wind Shear
Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with a change in altitude. Horizontal wind shear is a change in wind speed with a change in lateral position for a given altitude. Wind shear is a microscale meteorological phenomenon occurring over a very small distance, but it can be associated with mesoscale or synoptic scale weather features such as squall lines and cold fronts. It is commonly observed near microbursts and downbursts caused by thunderstorms, fronts, areas of locally higher low-level winds referred to as low-level jets, near mountains, radiation inversions that occur due to clear skies and calm winds, buildings, wind turbines, and sailboats. Wind shear has significant effects on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Troposphere
The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the planetary surface of the Earth, the average height of the troposphere is in the tropics; in the middle latitudes; and in the high latitudes of the polar regions in winter; thus the average height of the troposphere is . The term ''troposphere'' derives from the Greek words ''tropos'' (rotating) and ''sphere, sphaira'' (sphere) indicating that rotational turbulence mixes the layers of air and so determines the structure and the phenomena of the troposphere. The rotational friction of the troposphere against the planetary surface affects the flow of the air, and so forms the planetary boundary layer (PBL) that varies in height from hundreds of meters up to . The measures of the PBL vary according to the latitude, the landform, and the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
