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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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trough
Trough may refer to: In science * Trough (geology), a long depression less steep than a trench * Trough (meteorology), an elongated region of low atmospheric pressure * Trough (physics), the lowest point on a wave * Trough level (medicine), the lowest concentration of a medicine is present in the body over time * Langmuir-Blodgett trough, a laboratory instrument In politics * Trough (economics), the lowest turning point of a business cycle * as metaphor for political corruption, in the contexts of crony capitalism, nepotism, and public economics Other uses * Bread trough or dough trough, rectangular receptacle with a shallow basin, used in breadmaking * Trough (food) or manger, a container for animal feed * Watering trough, a receptacle of drinking water for domestic and non-domestic livestock * Battle of the Trough, a 1756 skirmish of the French and Indian War in West Virginia * Sleightholme Beck Gorge - The Troughs, a Site of Special Scientific Interest in the Teesdale dist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geographic Saddle
The saddle between two hills or mountains is the region surrounding the saddle point, the lowest point on the line tracing the drainage divide (the col) connecting the peaks. When, and if, the saddle is navigable, even if only on foot, the saddle of a (optimal) pass between the two massifs, is the area generally found around the lowest route on which one could pass between the two summits, which includes that point which is a mathematically when graphed a relative high along one axis, and a relative low in the perpendicular axis, simultaneously; that point being by definition the col of the saddle. Topography A saddle is the lowest area between two highlands (prominences or peaks) which has two wings which span the divide (the line between the two prominences) by crossing the divide at an angle, and, so is concurrently the local highpoint of the land surface which falls off in the lower direction. That is, the drainage divide is a ridge along the high point of the saddle, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclone
In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anticyclone). Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale (the synoptic scale). Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars, Jupiter, and Neptune. Cyclogenesis is the process of cyclone formation and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Wave
A tropical wave (also called easterly wave, tropical easterly wave, and African easterly wave), in and around the Atlantic Ocean, is a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which moves from east to west across the tropics, causing areas of cloudiness and thunderstorms. Tropical waves form in the easterly flow along the equatorial side of the subtropical ridge or belt of high air pressure which lies north and south of the Intertropical Convergence Zone (ITCZ). Tropical waves are generally carried westward by the prevailing easterly winds along the tropics and subtropics near the equator. They can lead to the formation of tropical cyclones in the north Atlantic and northeastern Pacific basins. A tropical wave study is aided by Hovmöller diagrams, a graph of meteorological data. West-moving waves can also form from the tail end of frontal zones in the subtropics and tropics, and may be referred to as easterly wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ridge (meteorology)
A ridge or barometric ridge is a term in meteorology describing an elongated area of relatively high atmospheric pressure compared to the surrounding environment, without being a closed circulation. It is associated with an area of maximum anticyclonic curvature of wind flow. The ridge originates in the center of an anticyclone and sandwiched between two low-pressure areas, and the locus of the maximum curvature is called the ''ridge line''. This phenomenon is the opposite of a trough. Description Ridges can be represented in two ways: * On surface weather maps, the pressure isobars form contours where the maximum pressure is found along the axis of the ridge. * In upper-air maps, geopotential height isohypses form similar contours where the maximum defines the ridge. Related weather Given the direction of the winds around an anticyclonic circulation and the fact that weather systems move from west to east: *ahead of an upper-ridge, the airflow that comes from the polar regi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Cyclone
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (), typhoon (), tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean, South Pacific, or (rarely) South Atlantic, comparable storms are referred to simply as "tropical cyclones", and such storms in the Indian Ocean can also be called "severe cyclonic storms". "Tropical" refers to the geographical origin of these systems, which form almost exclusively over tropical seas. "Cyclone" refers to their winds moving in a circle, whirling round ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convection Cell
In the field of fluid dynamics, a convection cell is the phenomenon that occurs when density differences exist within a body of liquid or gas. These density differences result in rising and/or falling currents, which are the key characteristics of a convection cell. When a volume of fluid is heated, it expands and becomes less dense and thus more buoyant than the surrounding fluid. The colder, denser part of the fluid descends to settle below the warmer, less-dense fluid, and this causes the warmer fluid to rise. Such movement is called convection, and the moving body of liquid is referred to as a ''convection cell''. This particular type of convection, where a horizontal layer of fluid is heated from below, is known as Rayleigh–Bénard convection. Convection usually requires a gravitational field, but in microgravity experiments, thermal convection has been observed without gravitational effects. Fluids are generalized as materials that exhibit the property of flow; however, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclogenesis
Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low-pressure area). Cyclogenesis is an umbrella term for at least three different processes, all of which result in the development of some sort of cyclone, and at any size from the microscale to the synoptic scale. * Tropical cyclones form due to latent heat driven by significant thunderstorm activity, developing a warm core. * Extratropical cyclones form as waves along weather fronts before occluding later in their life cycle as cold core cyclones. * Mesocyclones form as warm core cyclones over land, and can lead to tornado formation. Waterspouts can also form from mesocyclones, but more often develop from environments of high instability and low vertical wind shear. The process in which an extratropical cyclone undergoes a rapid drop in atmospheric pressure (24 millibars or more) in a 24-hour period is referred to as explosive cyclogenesis, and is usually present during the formation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adiabatic Process
In thermodynamics, an adiabatic process (Greek: ''adiábatos'', "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work.. A translation may be founhere. Also a mostly reliabltranslation is to be foundin As a key concept in thermodynamics, the adiabatic process supports the theory that explains the first law of thermodynamics. Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation".Bailyn, M. (1994), pp. 52–53. For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings. In meteorology and oceanography, adiabatic cooling produces condensation of moisture or salinity, oversatu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Westerlies
The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend towards the poles and steer extratropical cyclones in this general manner. Tropical cyclones which cross the subtropical ridge axis into the westerlies recurve due to the increased westerly flow. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. The westerlies are strongest in the winter hemisphere and times when the pressure is lower over the poles, while they are weakest in the summer hemisphere and when pressures are higher over the poles. The westerlies are particularly strong, especially in the Southern Hemisphere (called also 'Brave West winds' at striking Chile, Tasmania and New Zealand), in areas where land is absent, because land amplifies the flow pattern, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Waves
A tropical wave (also called easterly wave, tropical easterly wave, and African easterly wave), in and around the Atlantic Ocean, is a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which moves from east to west across the tropics, causing areas of cloudiness and thunderstorms. Tropical waves form in the easterly flow along the equatorial side of the subtropical ridge or belt of high air pressure which lies north and south of the Intertropical Convergence Zone (ITCZ). Tropical waves are generally carried westward by the prevailing easterly winds along the tropics and subtropics near the equator. They can lead to the formation of tropical cyclones in the north Atlantic and northeastern Pacific basins. A tropical wave study is aided by Hovmöller diagrams, a graph of meteorological data. West-moving waves can also form from the tail end of frontal zones in the subtropics and tropics, and may be referred to as easterly wave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Positive Vorticity Advection
Positive vorticity advection, or PVA, is the result of more cyclonic values of vorticity advecting into lower values of vorticity. It is more generally referred to as "Cyclonic Vorticity Advection" (CVA). In the Northern Hemisphere this is positive, whilst in the Southern Hemisphere it is negative. Development Vorticity in the atmosphere is created in three different ways, which are named in their resultant vorticity. These are; Coriolis vorticity, curvature vorticity, and shear vorticity. For example, at the base of a trough, there is curvature and shear vorticity. Curvature vorticity is due to the increasing cyclonic turning as an air parcel enters the trough base. The maximum counter-clockwise spin (positive vorticity in the Northern Hemisphere) is at the trough base. Shear vorticity is caused by the difference in wind speed between air moving through the trough base (typically a jet or jet finger) and slower moving air on either poleward and equatorward side of the faster flow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
