- 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, ...
The level at which a parcel of air lifted dry-adiabatically until saturated and saturation-adiabatically thereafter would first become warmer than its surroundings in a conditionally unstable atmosphere. On a thermodynamic diagram the level of free convection is given by the point of intersection of the process curve, representing the process followed by the ascending parcel, and the sounding curve, representing the lapse rate of temperature in the environment. From the level of free convection to the point where the ascending parcel again becomes colder than its surroundings the atmosphere is characterized by latent instability. Throughout this region the parcel will gain kinetic energy as it rises. See conditional instability, convective condensation level; compare level of free sink.
Industry:Weather
A special configuration in a line of convective storms that indicates the presence of a low pressure area and the possibility of damaging winds and tornadoes. In response to very strong outflow winds behind it, a portion of the line may bulge outward forming a bow echo.
Industry:Weather
The ratio of the power received in the orthogonal, or cross-polarized, channel to that received in the transmission, or copolarized, channel of a dual- channel radar, when a linearly polarized signal is transmitted. Because the main component of the linearly polarized, backscattered signal from hydrometeors has the same polarization as the transmitted polarization, the linear depolarization ratio yields a value less than unity or, equivalently, a negative decibel quantity. Note that relative to the receiver channels of the radar the linear depolarization ratio is defined inversely to the circular depolarization ratio.
Industry:Weather
The level at which a parcel of moist air lifted dry-adiabatically would become saturated. On a thermodynamic diagram it is located at the point of intersection of the dry adiabat through the point representing the parcel's original pressure and temperature with the saturation mixing ratio line having the same value of the mixing ratio as the parcel. The pressure and temperature at the lifting condensation level are usually called the condensation pressure and condensation temperature, respectively, and the corresponding point on a thermodynamic diagram is called either the characteristic point, adiabatic saturation point, or adiabatic condensation point. See convective condensation level, conditional instability, saturation level.
Industry:Weather
The range of altitudes within which the lifting condensation level (LCL) occurs for different air parcels rising from near the surface. Due to natural variability and land-use heterogeneity, air parcels at different horizontal locations near the ground usually have slightly different temperatures and humidities. As a result, each air parcel has its own LCL. Over a town, for example, LCLs might vary from 1000 m over an irrigated park to 1400 m over a paved parking area, thus giving a 400 m thick LCL zone centered at 1200 m. This implies that cumulus clouds formed from rising surface-layer air will have slightly different cloud-base altitudes within a region. While it is difficult to see this effect when observed from the ground, it is very obvious to aircraft flying at the average cloud-base altitude.
Industry:Weather
Ten minutes of AVHRR data at full resolution (1. 1 km at nadir) stored on digital tape recorders for subsequent playback to NOAA Command and Data Acquisition ground stations.
Industry:Weather
A unit of energy in the International System of Units (SI). One kilojoule is equal to 103 joules, or to 1010 ergs, or to 238. 9 calories.
Industry:Weather
A unit of frequency equal to one thousand (103) cycles per second. It is most commonly used in connection with radio wave frequencies.
Industry:Weather
An absolute temperature scale independent of the thermometric properties of the working substance. On this scale, the difference between two temperatures T1 and T2 is proportional to the heat converted into mechanical work by a Carnot engine operating between the isotherms and adiabats through T1 and T2. A gas thermometer utilizing a perfect gas has the same temperature scale. For convenience the Kelvin degree is identified with the centigrade degree. The ice point in the Kelvin scale is 273. 16 K. See absolute zero; see also centigrade temperature scale.
Industry:Weather
