- 업종: Earth science
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The force that causes acceleration from higher to lower pressure in a fluid such as the air. It arises because of a pressure gradient or change between higher and lower pressure. As an analogy, consider the pressure gradient that exists at the nozzle of a vacuum cleaner when it is turned on. A motor inside creates a region of relatively low pressure contrasted with the region of higher pressure outside. The dust and air molecules outside the vacuum, being at a higher pressure, feel a force pulling toward the low pressure inside the vacuum. This is a pressure gradient force. In the atmosphere, regions of high and low pressure form ultimately as a result of unequal heating. In moving from a high pressure region to a low pressure region, the motion is said to be along the pressure gradient. The pressure gradient force itself points in the direction of the lower pressure. In the vacuum cleaner example, this is evidenced by the fact that air is sucked into the lower pressure inside. The magnitude of the pressure gradient force is proportional to the magnitude of the pressure gradient itself. The lower the pressure inside the vacuum cleaner, the more powerful the vacuum will be. In the atmosphere, pressure gradient is related to a quantity called geopotential height. The pressure gradient force is proportional to the geopotential height gradient.
Industry:Earth science
The four main navigational directions (North, East, South, and West) found on a compass or a map.
Industry:Earth science
The Fourier transform of the kinetic energy field. The power spectrum provides a useful diagnostic to measure a what length scales energy is concentrated and, in turbulent flow, over what length scales energy is transferred and dissipated.
Industry:Earth science
The global oceanic conveyer belt, is a unifying concept that connects the ocean's surface and thermohaline (deep mass) circulation regimes, transporting heat and salt on a planetary scale. Oceanic Conveyor Belt.
Industry:Earth science
The greenhouse effect causes the atmosphere to trap more heat energy at the Earth's surface and within the atmosphere by absorbing and re-emitting longwave energy. Of the longwave energy emitted back to space, 90% is intercepted and absorbed by greenhouse gases. Without the greenhouse effect the Earth's average global temperature would be -18° Celsius, rather than the present 15° Celsius. In the last few centuries, the activities of humans have directly or indirectly caused the concentration of the major greenhouse gases to increase. Scientists predict that this increase may enhance the greenhouse effect making the planet warmer. Some experts estimate that the Earth's average global temperature has already increased by 0. 3 to 0. 6° Celsius, since the beginning of this century, because of this enhancement.
Industry:Earth science
The height of a given point in the atmosphere in units proportional to the potential energy of unit mass (geopotential) at this height, relative to sea level. In the CGS system, the relation between the geopotential height H and the geometric height Z is where g is the acceleration of gravity, so that the two heights are numerically interchangeable for most meteorological purposes. Also, 1 geopotential meter is equal to 0. 98 dynamic meter. At present, by convention of the World Meteorological Organization, the geopotential height unit is used for all aerological reports.
Industry:Earth science
The Holocene epoch is a geological period that runs from the present day back to about 10,000 years BP. It forms the upper division of the Quaternary era.
Industry:Earth science
The horizontal extent of internal gravity waves, below which vertical overturning of waves may occur and above which overturning is inhibited by stratification. The length scale is proportional to \epsilon^(1/2)/N^(3/2) in which \epsilon is the flux of energy from large to small scales and N is the buoyancy frequency.
Industry:Earth science
The horizontal wind velocity for which the Coriolis force exactly balances the horizontal pressure gradient force.
Industry:Earth science
The lateral movement of sediments on a beach when the angles of swash and backwash differ.
Industry:Earth science
