- Settore: Education
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Founded in 1876, Texas A&M University is a U.S. public and comprehensive university offering a wide variety of academic programs far beyond its original label of agricultural and mechanical trainings. It is one of the few institutions holding triple federal designations as a land-, sea- and ...
One of five vertical ecological zones into which the deep sea is sometimes divided. The epipelagic zone extends from the surface downward as far as sunlight penetrates during the day. It is a very thin layer, less than 100 meters thick in the eastern parts of the oceans in regions of upwelling and high productivity and up to 200 meters thick in clear subtropical areas. The endemic species of this zone either do not migrate or perform only limited vertical migrations, although there are many animals that do invade the epipelagic zone from deeper layers during the night or pass their early development stages in the photic zone. The epipelagic zone overlies the mesopelagic zone.
Industry:Earth science
The time it takes for a system to re-equilibrate after being subject to a perturbation. This is usually expressed in terms of an e-folding time. Some typical equilibration times are: the atmosphere, 11 days; the ocean mixed layer, 7-8 years; the deep ocean, 300-1000 years; mountain glaciers, 300 years; ice sheets, 3000 years; the Earth's mantle, 30 million years.
Industry:Earth science
In meteorology, the equivalent temperature of an air sample when it is brought adiabatically to a pressure of 1000 mb. It is a conservative property for both dry and saturated adiabatic processes.
Industry:Earth science
In numerical modeling, an integration algorithm that temporally advances an approximate solution via discrete steps using only information from previous time steps. These are computationally simpler than implicit schemes but require shorter time stepping intervals.
Industry:Earth science
Waves in the nearshore zone at periods ranging from 100 to 1000 seconds. These were first discovered in 1986 as substantial energy in the velocity field in that period range, although no accompanying sea surface elevation signal was found, and their celerities were about an order of magnitude too slow to be consistent with a gravity wave explanation. They were eventually identified as shear waves arising from an instability of the strong mean longshore current. The dynamics are analogous to large scale flows, but with the role of the Coriolis force played by the shear of the longshore current.
Industry:Earth science
Most generally this is a phenomenon where the output of a system is fed or cycled back into the input of the system, thus changing the output, etc. This is equivalent to saying that a system is nonlinear.
Industry:Earth science
A numerical approximation method in which data is represented over some domain by a discrete series of functions. The domain is divided into a finite number of subregions called elements, whence the name. A series of functions is built up by defining a simple function, e.g. a low-order polynomial, on each element and requiring continuity between functions on adjacent subregions. The points where values are used to define the functions are conventionally called nodes and the defining parameters nodal values.
Finite elements are distinguished from spectral methods in that their approximations are local and not global, and they are distinguished from finite differences because the function is defined over a whole region rather than just a discrete points. Their use is more prevalent in modeling solid structures such as buildings or airplanes than it is for geophysical fluid flow, although several authors have constructed circulation models using finite elements. Perhaps their greatest advantage is the relative ease with which highly irregular boundaries can be handled as opposed to with the aforementioned spectral and finite difference methods.
Industry:Earth science
One of the four principal types of estuaries as distinguished by prevailing flow conditions. This type features a relatively stagnant, deep water mass overlain by a thin river runoff flow, e.g. prevailing summer conditions for the Norwegian fjords.
Industry:Earth science
An ad hoc procedure by which the values of dependent variables at the air-sea interface in coupled atmosphere-ocean model runs are adjusted to better conform to observed values. For example, heat flux is corrected by first running the ocean model and calculating the heat flux needed to correct the differences between the observed and calculated surface temperatures. Next the atmospheric model is run with observed values of SST and the net heat flux from the atmosphere is calculated. The coupled model is then run with the difference between these ocean and atmospheric heat fluxes added to those calculated by the coupled model at each time step. A similar procedure can be followed with other variables. These methods are designed to remove most of the tendency of coupled models to drift towards their own climate replete with systematic errors. The most difficult area to apply this procedure is over ice. It is expected that this will become much less of an issue as the model components are improved.
Industry:Earth science
In physical oceanography, this refers to the water trapped between the depths of the summer and winter mixed layers. This is a key feature in the formation of Central Water via the process of subduction.
Industry:Earth science
