- 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 mountain-wave cloud form that occurs along the east slopes of the Rocky Mountains, particularly in the Montana–Alberta area, where the range runs roughly north–south. The arch cloud has a sharp western (upwind) edge and a great cross-wind extent in the lee of and parallel to the Rockies. Arch clouds can stretch a few hundred km or more north–south as measured from the ground and from satellite. The arch refers to the shape of the western edge of the wave cloud as seen by an observer looking westward from the ground on the plains east (to the lee) of the mountains. The arch is especially noticeable when the blue sky to the west of it is completely clear of other cloud layers. Glider pilots sometimes refer to the clear area as the “window. ” The distinctive shape of the arch is due to the cloud height (usually middle or high cloud), its large cross-wind extent along the horizon, and the perspective of the observer, who sees the cloud and the mountain range converge with distance to the north and south. The arch cloud often presages a chinook. Because of the rapid temperature rises associated with a chinook, the arch has an important place in local weather lore as a predictor.
Industry:Weather
A name for the mistral in Catalonia, Narbonne, and parts of Provence (southern France and northeastern Spain). It is very violent and turbulent in the Aude Valley below Carcassonne with gusts often reaching 22–25 m s−1 (50–55 mph). It is cold in winter, hot in summer, always dry and clear. A similar northerly wind in Spain is the cierzo.
Industry:Weather
A more or less regular periodic array of atoms, molecules, or ions, usually forming a solid. In everyday parlance crystal is used in a bewildering variety of ways, sometimes contradictory. Fine glassware is called crystal, although glass, an amorphous solid, is the antithesis of a crystal. A solid with facets exhibiting external symmetry may be called a crystal, although a solid without such facets may still be a crystal. A pure liquid such as water is said to be crystal clear even though transparency is not an essential property of a crystal.
Industry:Weather
A modification of growing degree-days (GDD) with both upper and lower temperature thresholds. All temperatures above 86°F (30°C) are set to 86°F (30°C) and all temperatures below 50°F (10°C) are set to 50°F (10°C) before calculation of daily mean temperature. The reference temperature (base temperature) for corn heat units is 50°F (10°C). See degree-day.
Industry:Weather
A monthly broadcast of the mean values of the meteorological elements during the preceding month for stations of the national weather services belonging to the World Meteorological Organization (WMO). The messages are disseminated worldwide through the Global Telecommunications System (GTS) as soon as possible after the close of a month, but not later than the fifth of the following month. This program was recommended to the predecessor of the WMO (the International Meteorological Organization) and widely implemented during 1936–39. The program, the elements broadcast, and the codes utilized have been revised several times since the program's implementation. The elements broadcast by a principal climatological station, according to the 1995 edition of the Manual on Codes (WMO Publication No. 306), include atmospheric pressure, temperature (means and extremes of daily mean, maximum, and minimum), wind speed, vapor pressure, precipitation (monthly total, frequency group (quintile) within which it falls, and extreme daily amount), sunshine duration, standard deviation of temperature, number of days with thunderstorms and hail, and number of days with precipitation, temperatures, snow depth, visibility, and wind speed beyond various thresholds. Provision is also made for the issuance of comparable normals, as far as possible, for the most recent climatological standard normal period (i.e., 1901– 30, 1931–60, 1961–90, etc. ).
Industry:Weather
A model used to make forecasts or simulations of climate. Most climate models are closely related to NWP models. In general, the equations for the atmosphere are those for momentum, continuity, the equation of state, the law of thermodynamics, and water vapor continuity, although simplified sets of governing equations may also be used. Depending on the climate timescale of interest, the atmospheric model may be coupled to similar models for the ocean (including the deep ocean for timescales greater than a year), the land surface and biosphere, land snow and ice, and sea ice. For longer timescales, variation in external forcing factors (solar radiation) may also be important. Because climate models are generally integrated for periods of many years, they have traditionally been run at lower resolution than NWP models to reduce computational costs.
Industry:Weather
A modern, self-calibrating pyrheliometer or device for measuring direct solar radiation. The receiver (cavity) is typically conical in shape with precision temperature sensors and heaters. Operating at an equilibrium temperature, direct electrical power to the heater is decreased if solar radiation is added to the receiver (or added if solar radiation is removed). The electrical power necessary to maintain equilibrium is equivalent to the change in incident solar radiation.
Industry:Weather
A method used for measurements of surface water discharges, by injecting a conservative tracer at a constant rate. The change in concentration of samples collected downstream, relative to the original injected fluid, is used to calculate the flow rate along that reach.
Industry:Weather
A method of representing unresolved convection in atmospheric models by imposing large-scale vertical profiles when convection occurs. As originally developed, convective adjustment was applied when modeled lapse rates became adiabatically unstable. New temperatures were calculated for unstable layers by conserving static energy and imposing an adiabatic lapse rate. If, in addition, humidities exceeded saturation, they were adjusted to saturation, with excess water removed as precipitation. A related adjustment, (stable saturated adjustment), for stable layers with water vapor exceeding saturation, returned them to saturation, also conserving energy. More recently, convective adjustments have been developed that adjust to empirically based lapse rates, rather than adiabatic lapse rates, while still maintaining energy conservation. Convective adjustment is generally applied to temperature and humidity but, in principle, can also be applied to other fields affected by convection.
Industry:Weather
A method used to estimate the true value of a quantity with measured or observed values that have statistical fluctuations and outliers that are presumed to be due to measurement error, extraneous signals, or noise. The consensus averaging technique examines the set of all measured values and finds the largest subset with values within a predetermined interval of each other. If that subset has fewer than a predetermined number of values, then the entire set of measurements is rejected; otherwise, the selected subset is averaged to obtain an estimate of the true value of the measured quantity. For this technique to be valid, the true value must not change greatly during the time period over which the measurements are taken. Consensus averaging has been used in wind profiling to determine an estimate of the wind velocity from several measurements of the Doppler shift of the radar signal, which is often dominated by noise and contaminated by interfering radio signals, airplanes, birds, etc.
Industry:Weather
