Radar Meteorology Exam 1

Term
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Why does the radar send pulses of energy instead of continuous streams of electromagnetic energy?
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Terms in this set (27)
Why does the radar send pulses of energy instead of continuous streams of electromagnetic energy?
It allows a radar system to display target distance/ range from the antenna
Since electromagnetic energy travels at a constant speed, target range is a function of _________ ___________.
elapsed time
What is the equation for calculating pulsing?
R = c times (et/2)

c = speed of light
et = elapsed time (divided by 2 since the energy must travel to and from a target)
What does the unambiguous range (Rmax) correspond to?
It corresponds to half the distance electromagnetic energy can travel between pulses
What is pulse repetition frequency (PRF)?
The rate at which pulses are broadcast; expressed in terms of the number of pulses transmitted per second
What is the radar beam defined by?
Half power points
What causes most of the clutter in close proximity to the radar?
Side lobes
The pulse volume has dimensions of _________ and _________
one pulse length in range, one beam width in both azimuth and height
How does the pulse volume change with distance from the dish?
The pulse volume will increase with increasing distance from the dish (beam spreading); pulse length remains constant
How is the resolution of the radar beam determined?
1/2 the pulse length and 1 beam width for azimuth and height
As the range of a target increases, how does the size of the radars sample volume change?IncreasesAs the range of a target increases, how does the ability of the radar to detect small-scale features change?DecreasesWhat happens to a radar pulse when it travels through the atmosphere?Some of its energy is lostHow does a radar pulse lose some of its energy when it travels through the atmosphere?This occurs as energy interacts with hydrometeors (precipitation particles like rain, snow, hail, cloud droplets) and lithometeors (dust, ash, smoke)If the radar pulse interacts with these atmospheric constituents (like precip or dust), what happens to the energy associated with the radar pulse?With interactions comes some loss of energy by absorption from the atmospheric constituent; a lot of the energy will be scattered by the atmospheric constituentsWhat is backscattering?Energy returned and detected by the radarThe degree of backscatter is a function of (4):- size (diameter) - state (liquid, ice, or mixture) - shape (round, oblate, flat) - concentration (# per unit volume)What is precipitation detection?The degree to which radar can detect precipitation targetsWhat factors affect how precipitation is detected by radar (4)?- atmospheric conditions between radar and target - distance to target - precipitation characteristics - radar characteristicsWhat does sub-refraction mean?The beam is refracted less than it would be in the standard atmosphere (bent toward the earth less)What does a sub-refracted beam produce?A beam that is higher in altitude than standard for all radar anglesWhat happens to features on radar if the beam is sub-refracted?The upward curving of the beam results in storms tops (and other storm features) appearing lower on the radar display than they actually areWhat is super-refraction?The beam is refracted more than it would be in the standard atmosphere (bent toward the Earth more)What happens to features on radar if the beam is super-refracted?The downward bending of the beam results in storm tops and other storm features appearing higher on the display than they actually areWhat is the WSR-88D designed to detect?To detect the phase of returned signals and compute pulse-pulse phase changesWhat is a phase?A particular angular stage or point of advancement in a cycle; the fractional part of the angular period through which a wave has advanced, measured from the phase referenceWhat is the doppler dilemma?As you increase the pulse repetition frequency you reduce your usable length of the radar (less time for energy to strike and target and return to the radar)