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Rodwell–Hoskins Mechanism
Rodwell–Hoskins mechanism is a hypothesis about a climatic teleconnection between the Indian/Asian summer monsoon and the climate of the Mediterranean. It stipulates that ascending air in the monsoon region induces atmospheric circulation features named Rossby waves that expand westward and interact with the mean westerly winds of the midlatitudes, eventually inducing descent of the air. Descending air warms and its humidity decreases, thus resulting in a drier climate during the summer months. The interaction of this atmospheric flow with the topography such as the Atlas and Zagros mountains further modifies the effect. This hypothesis has been advanced to explain the dry climate of the eastern Mediterranean during the summer months, as other explanations involving the Hadley circulation are not plausible during that season. Together with sea and land surface feedbacks it may also explain the existence of deserts and subtropical anticyclones elsewhere in the world, as well a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teleconnection
Teleconnection in atmospheric science refers to climate anomalies being related to each other at large distances (typically thousands of kilometers). The most emblematic teleconnection is that linking sea-level pressure at Tahiti and Darwin, Australia, which defines the Southern Oscillation. History Teleconnections were first noted by the British meteorologist Sir Gilbert Walker in the late 19th century, through computation of the correlation between time series of atmospheric pressure, temperature and rainfall. They served as a building block for the understanding of climate variability, by showing that the latter was not purely random. Indeed, the term El Niño–Southern Oscillation (ENSO) is an implicit acknowledgment that the phenomenon underlies variability in several locations at once. It was later noticed that associated teleconnections occurred all over North America, as embodied by the Pacific–North American teleconnection pattern. In the 1980s, improved observati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. The biomass of phytoplankton and the presence of cool water in those regions allow upwelling zones to be identified by cool sea surface temperatures (SST) and high concentrations of chlorophyll-a. The increased availability of nutrients in upwelling regions results in high levels of primary production and thus fishery production. Approximately 25% of the total global marine fish catches come from five upwellings, which occupy only 5% of the total ocean area.Jennings, S., Kaiser, M.J., Reynolds, J.D. (2001) "Marine Fisheries Ecology." Oxford: Blackwell Science Ltd. Upwellings that are driven by coastal currents or diverging open oc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South American Monsoon
South is one of the cardinal directions or compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic ''*sunþaz'' ("south"), possibly related to the same Proto-Indo-European root that the word ''sun'' derived from. Some languages describe south in the same way, from the fact that it is the direction of the sun at noon (in the Northern Hemisphere), like Latin meridies 'noon, south' (from medius 'middle' + dies 'day', cf English meridional), while others describe south as the right-hand side of the rising sun, like Biblical Hebrew תֵּימָן teiman 'south' from יָמִין yamin 'right', Aramaic תַּימנַא taymna from יָמִין yamin 'right' and Syriac ܬܰܝܡܢܳܐ taymna from ܝܰܡܝܺܢܳܐ yamina (hence the name of Yemen, the land to the south/right of the Levant). Navigation By convention, the ''bottom or down-facing side'' of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Surface Temperature
Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a short distance of the shore. Localized areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth's oceans. Tropical cyclones can also cause a cool wake, due to turbulent mixing of the upper of the ocean. SST changes diurnally, like the air above it, but to a lesser degree. There is less SST variation on breezy days than on calm days. In addition, ocean currents such as the Atlantic Multidecadal Oscillation (AMO), can affect SST's on multi-decadal time scales, a major impact results from the global thermohaline ci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Etesian Wind
The etesians ( or ; grc, ἐτησίαι, etēsiai, periodic winds; sometimes found in the Latin form etesiae), ''meltemia'' ( el, ετησίες,μελτέμια; pl. of meltemi), or meltem ( Turkish) are the strong, dry north winds of the Aegean Sea, which blow from about mid-May to mid-September. The Etesian winds are a dominant weather influence in the Aegean Basin. They are at their strongest in the afternoon and often die down at night, but sometimes meltemi winds last for days without a break. Similar winds blow in the Adriatic and Ionian regions. Meltemi winds are dangerous to sailors because they come up in clear weather without warning and can blow at 7–8 Beaufort. Some yachts and most inter-island ferries cannot sail under such conditions. However, they often provide a good, steady sailing wind favored by leisure sailors. The word ''etesian'' ultimately derives from the Greek word ''etos'' "year", connoting the yearly fluctuation in frequency of appearance of thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anticyclonic
An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere as viewed from above (opposite to a cyclone). Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure. Mid-tropospheric systems, such as the subtropical ridge, deflect tropical cyclones around their periphery and cause a temperature inversion inhibiting free convection near their center, building up surface-based haze under their base. Anticyclones aloft can form within warm-core lows such as tropical cyclones, due to descending cool air from the backside of upper troughs such as polar highs, or from large-scale sinking such as a subtropical ridge. The evolution of an anticyclone depends upon variables such as its size, intensity, and extent of moist convec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orography
Orography is the study of the topographic relief of mountains, and can more broadly include hills, and any part of a region's elevated terrain. Orography (also known as ''oreography'', ''orology'' or ''oreology'') falls within the broader discipline of geomorphology. The term orography comes from the Greek: , hill, , to write. Uses Mountain ranges and elevated land masses have a major impact on global climate. For instance, the elevated areas of East Africa substantially determine the strength of the Indian monsoon.Srinivasan, J., Nanjundiah, Ravi S. and Chakraborty, Arindam (2005Impact of Orography on the Simulation of Monsoon Climate in a General Circulation Model''Indian Institute of Science'' In scientific models, such as general circulation models, orography defines the lower boundary of the model over land. When a river's tributaries or settlements by the river are listed in 'orographic sequence', they are in order from the highest (nearest the source of the river) to the l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isentropic Analysis
Isentropic analysis in meteorology is a technique to find the vertical and horizontal motion of airmasses during an adiabatic process above the planetary boundary layer. The change of state of air parcels following isentropic surfaces does not involve exchange of heat with the environment. Such an analysis can also evaluate the airmass stability in the vertical dimension and whether an air parcel crossing such a surface will result in convective or stratiform clouds. It is based on the study of weather maps or vertical cross-sections of the potential temperature values in the troposphere. On a synoptic scale, isentropic analysis is associated with weather fronts: warm fronts are found where the wind crosses lines of a chosen potential temperature from lower heights to higher ones, while cold fronts are where the wind crosses descending heights. Synoptic clouds and precipitations can thus be better found with these areas of advection than with conventional isobaric Isobar may refe ... [...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] |
Walker Circulation
The Walker circulation, also known as the Walker cell, is a conceptual model of the air flow in the tropics in the lower atmosphere (troposphere). According to this model, parcels of air follow a closed circulation in the zonal and vertical directions. This circulation, which is roughly consistent with observations, is caused by differences in heat distribution between ocean and land. It was discovered by Gilbert Walker. In addition to motions in the zonal and vertical direction the tropical atmosphere also has considerable motion in the meridional direction as part of, for example, the Hadley Circulation. The term "Walker circulation" was coined in 1969 by the Norwegian-American meteorologist Jacob Bjerknes. Walker's methodology Gilbert Walker was an established applied mathematician at the University of Cambridge when he became director-general of observatories in India in 1904. While there, he studied the characteristics of the Indian Ocean monsoon, the failure of whose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advection
In the field of physics, engineering, and earth sciences, advection is the transport of a substance or quantity by bulk motion of a fluid. The properties of that substance are carried with it. Generally the majority of the advected substance is also a fluid. The properties that are carried with the advected substance are conserved properties such as energy. An example of advection is the transport of pollutants or silt in a river by bulk water flow downstream. Another commonly advected quantity is energy or enthalpy. Here the fluid may be any material that contains thermal energy, such as water or air. In general, any substance or conserved, extensive quantity can be advected by a fluid that can hold or contain the quantity or substance. During advection, a fluid transports some conserved quantity or material via bulk motion. The fluid's motion is described mathematically as a vector field, and the transported material is described by a scalar field showing its distribution ov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
