- 行业: Weather
- Number of terms: 60695
- Number of blossaries: 0
- Company Profile:
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, ...
In radio terminology, or for lightning transients, electromagnetic waves received after they have been reflected by the ionosphere. Compare ground wave.
Industry:Weather
In radar, a change in the polarization state of a signal because of propagation through and interaction with an anisotropic medium, for example, a cloud of precipitation particles of nonspherical shape that have principal axes with a common alignment or preferred orientation. See depolarization, differential attenuation, differential phase shift.
Industry:Weather
In radar, the time after the transmission of a pulse for the receiver to regain its full sensitivity. Ordinarily the receiver is turned off during pulse transmission to protect it from the strong transmitted signal and is turned back on as soon as the transmitter is turned off. The recovery time is the transient time during which full receiver sensitivity is restored. Because the receiver is not operating at its full sensitivity at times shorter than the recovery time, quantitative reflectivity measurements at close ranges are difficult or impossible. Through the use of fast switches, recovery times may be in the order of a fraction of a microsecond, so that the minimum range for quantitative measurements can be as small as a few tens of meters.
Industry:Weather
In radar, the power scattered by a target, or the amount of this power arriving at the antenna of the receiver.
Industry:Weather
In radar, the amount of power received at the antenna after being scattered by a target. This power is normally on the order of microwatts as compared with the kilowatts or megawatts of transmitted power. By convention, received power is measured in decibels relative to a reference value of 1 mW, that is, in dBm. The average received power is proportional to the radar reflectivity of the target, while fluctuations in the received power are caused by relative motions among the individual scattering elements that make up the target.
Industry:Weather
In radar, sodar, or lidar, the period of time during which a pulse is being transmitted.
Industry:Weather
In radar, sodar, or lidar, the extent of a transmitted pulse, measured in units of length. So defined, the pulse length is the pulse duration times the velocity of propagation of the energy. However, the term pulse length is sometimes used in place of pulse duration.
Industry:Weather
In radar, sodar, or lidar a single short-duration transmission (or burst) of energy. A pulse is characterized by its radio frequency, pulse repetition frequency, pulse duration, and peak power.
Industry:Weather
In radar, coordinated scanning in azimuth and elevation so that much of the space in the hemisphere above a ground-based radar is surveyed. In a common form of spiral scanning, the antenna rotates continuously in azimuth around a full circle while the elevation is slowly increased from the horizontal to a high angle.
Industry:Weather
In radar, an azimuth sector with no echoes because the transmitted signal is masked by local prominences such as hills or buildings.
Industry:Weather
