- 行业: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
A recording instrument combining, on one record, the variation of atmospheric temperature and humidity content as a function of time. The most common hygrothermograph is a hair hygrograph combined with a thermograph.
Industry:Weather
A record and graphical representation of discharge as a function of time at a specific location, for example, the discharge at a point in a stream or the discharge from a pumping well.
Industry:Weather
A recirculation system between the South Equatorial Current and the North Equatorial Countercurrent in the extreme west of the Pacific Ocean, east of Halmahera. The circulation, about 1000 km in diameter, is clockwise from April–November but reverses during December–March when the Philippines experience monsoon winds blowing from the northeast in the Northern Hemisphere and from the northwest south of the equator.
Industry:Weather
A range of eddies in the scalar spectrum in which the diffusivity is unimportant and that are therefore simply advected by the mean flow; so called as an analogy with the inertial subrange of the turbulence kinetic energy spectrum.
Industry:Weather
A radar for measuring many of the properties of the ionosphere and the neutral upper atmosphere. The radar uses a technique that is much more sensitive and has greater spatial resolution than more conventional ionosondes, but requires powerful radar transmitters and large antennas.
Industry:Weather
A radar designed for accurate determination of target altitude. The beamwidth of such radars is generally much narrower in the vertical than in the horizontal.
Industry:Weather
A property of the steady state of a system such that certain disturbances or perturbations introduced into the steady state will increase in magnitude, the maximum perturbation amplitude always remaining larger than the initial amplitude. The method of small perturbations, assuming permanent waves, is the usual method of testing for instability; unstable perturbations then usually increase exponentially with time. An unstable nonlinear system may or may not approach another steady state; the method of small perturbations is incapable of making this prediction. The small perturbation may be a wave or a parcel displacement. The parcel method assumes that the environment is unaffected by the displacement of the parcel. The slice method has occasionally been used as a modification of the parcel method to gain a little information about the interaction of parcel and environment. Stability as defined above is an asymptotic concept; other definitions are possible. Precision is required of the user, and caution of the reader. The concept of instability is employed in many sciences. In meteorology the reference is usually to one of the following. Static instability (or hydrostatic instability) of vertical displacements of a parcel in a fluid in hydrostatic equilibrium. (See conditional instability, absolute instability, convective instability, buoyant instability. )
Hydrodynamic instability (or dynamic instability) of parcel displacements or, more usually, of waves in a moving fluid system governed by the fundamental equations of hydrodynamics, to which the quasi-hydrostatic approximation may or may not apply. (See Helmholtz instability, inertial instability, shearing instability, baroclinic instability, barotropic instability, rotational instability. )
The space scale of unstable waves is important in meteorology: Thus Helmholtz, baroclinic, and barotropic instability give, in general, unstable waves of increasing wavelength. The timescale is also important: A perturbation that grows for two days before dying out is effectively unstable for many meteorological purposes, but this is an initial-value problem and one cannot assume the existence of permanent waves. These meteorological types of hydrodynamic instability must not be confused with the phenomenon often referred to by mathematicians and physicists by the same term. A great deal of study has been devoted to the problem of the onset of turbulence in simple flows under laboratory conditions, and here viscosity is a source of instability. See computational instability.
Industry:Weather
A process in which the total entropy of the universe (system and its surroundings) increases. All real processes are irreversible.
Industry:Weather
A process from which more ice particles are produced from existing ice crystals in clouds. Sometimes known as ice enhancement. The process is inferred from the observation that ice particle concentration often exceeds that of ice nuclei, sometimes by several orders of magnitude. Currently the following mechanisms are thought to be responsible for the ice multiplication phenomenon: 1) mechanical fracturing of ice crystals during evaporation; 2) shattering or partial fragmentation of large drops during freezing; and 3) ice splinter formation during the riming of ice particles (Hallett–Mossop process).
Industry:Weather
