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Weather Module 3 > Radar Imagery Theory > Flashcards

Radar Imagery Theory Flashcards

1
Q

What does RADAR stand for?

A

Radio Detection and Ranging

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2
Q

What does PPI stand for?

A

Plan Position indicator

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3
Q

What is a PPI?

A

A display of echoes superimposed over a grid of geography and viewed from overhead

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4
Q

What does CAPPI stand for?

A

Constant altitude Plan Position Indicator

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5
Q

What are the dimensions of the CAPPI area?

A

1.5km vertically

130km horizontally

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6
Q

What is an Echo Top?

A

A representation of the highest altitude where detectable precipitation is observed

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7
Q

In a CAN/US composite what are the significant points?

A
  • Canadian echoes are CAPPI, US echoes are PPI
  • resolution is 4.2nm per pixel
  • Always set on rain
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8
Q

what type of radar are modern radars and how do they work

A
  • Pulsed RADAR

- Short bursts of energy are transmitted and there are long silent periods to listen for returned energy

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9
Q

Why are those type of radar used?

A

Only one antenna needed and it uses much less power

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10
Q

List the 5 components of a RADAR system

A 
Transmitter
Receiver
Antenna
Processor
Display
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11
Q

Define wavelength

A

The distance between one crest and the next, or. one trough and the next

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12
Q

Define frequency

A

The path that the wave travels in one wavelength is called a cycle and the number of cycles in a given unit of time(one second) is the frequency (hz)

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13
Q

What are the advantages and disadvantages of short wavelengths?

A
  • It can detect light precipitation

- It is severely weakened or attenuated by precip

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14
Q

What are the advantages and disadvantages to long wavelengths?

A
  • The greater its capacity to detect heavy precip

- it burns through most light precip

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15
Q

what are the 3 wavelengths and which do we use in Canada? What is its letter band indicator?

A

-3cm is good for snow
-10cm is good for showers
5cm is the one we use.
C band

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16
Q

What is the pulse length?

A

The duration of time that the RADAR is radiating

17
Q

What kind of shape does the radar beam have?

A

Conical

18
Q

The horizontal and vertical dimensions of the RADAR beam are referred to as the

A

Beam Width

19
Q

What is normal propagation?

A

4/3 the earth’s curvature

20
Q

what is anomalous propagation

A

when the RADAR beam is bent more or less than usual due to unusual temperature or humidity lapse rate.

21
Q

What are the 2 types of anomalous propagation?

A
  • Sub refraction

- Super refraction

22
Q

Radar targets will affect return power as a result of 3 factors:

A
  • Number of drops or flakes
  • composition
  • size
23
Q

which hydrometeor reflects better, rain or snow?

A

Rain. Snow reflects gives a return 1/5 that of rain

24
Q

the reflective capability of hydrometeors listed in order is:

A 
Large Hail
Rain
Small hail
snow
clouds
25
Q

List the 3 types of attenuation

A

Range
Absorption
scattering

26
Q

Define attenuation

A

A lessening of the concentration of energy per unit volume of the beam.

27
Q

what is the energy that is returned to the radar, and captured by the antenna for processing

A

Backscatter

28
Q

Define distortion

A

The misrepresentation of the target in any of its parameters

29
Q

What are the 2 categories of distortion

A

Radar design

Propagation characteristics

30
Q

What are the 3 distortions due to radar design?

A
  • Beam width
  • Pulse length
  • processor distortion
31
Q

What are the 4 propagation characteristic distortions

A
  • Range
  • Precip attenuation
  • Fringing
  • Earth’s curvature
32
Q

What is used on all canadian radar to help with range distortion?

A

STC (sensitivity Time Control)

33
Q

Define extraneous echo

A

Any echo not derived from clouds or precip

34
Q

What are the 3 types of extraneous echoes?

A
  • Angel echoes
  • Clutter
  • Second trip echoes
35
Q

How many radar sites are there in Canada?

A

31

36
Q

What are the 2 types of radar used in the USA?

A 
5 cm (S-band)
10cm (C-band)

Weather Module 3 (10 decks)

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