Radar Exam 1

Question 0

What wavelengths are c-band, x-band, & s-band?

Answer 0

5cm, 3cm, and 10cm respectively

Question 1

What does radar stand for?

Answer 1

Radio Detection and Ranging

Question 2

What wavelength do WSR-88D radars function on?

Answer 2

S-band (10cm)

Question 3

What are the basic functions of a radar?

Answer 3

Measure, identify, locate, detect, display

Question 4

What are the components of a radar?

Answer 4

Transmitter, antenna, receiver, and indicator

Question 5

What do each component of radar do? (RIAT)

Answer 5

Receiver- detects and amplifies and converts microwave signal
Indicator- displays signal
Antenna- focuses the beam and receives a fraction of the power
Transmitter- produces the power

Question 6

What are the types of radar?

Answer 6

Monostatic, bistatic (2 antennas), continuous, pulse, Doppler, phased array, polarmetric, wind profilers, and lidar

Question 7

What’s the difference between Doppler radar and phased array radars?

Answer 7

Doppler is based off of the Doppler shift while phased array does the same but collects data in 1/6 the time

Question 8

What region in the electromagnetic spectrum do radars transmit at?

Answer 8

Microwave

Question 9

What affects the radar beam?

Answer 9

Curvature of the earth and refraction of light

Question 10

What is PRF?

Answer 10

Pulse repetition frequency. Tells the time in between when pulses are sent out (# of pulses sent out per second)

Question 11

What are the elevation and azimuth angle?

Answer 11

Elevation is angle off of ground

Azimuth is angle from top to direction of beam

Question 12

What do each variable in the R.E for point target mean? Pt, Ae, lambda, sigma, and r

Answer 12

Pt is transmitted power in watts
Ae is effective area (where radar works)
Lambda is wavelength
Sigma is radar cross section
r is radius of the sphere from target

Question 13

What is gain?

Answer 13

Power flux density for a directional antenna/ power flux density for an isotropic antenna

Question 14

What do the variables tau, theta, phi, c, and K stand for?

Answer 14

Tau- pulse duration in micro seconds
Theta and phi are arc length between half power points and the beam
C is the speed of light
K is a complex number representing the scattering and absorption characteristics of the medium

Question 15

What are the assumptions of the radar equation?

Answer 15

1. Particles are all spheres
2. Particles are sufficiently small compared to the wavelength of the scattering ~1/6 size. (Rayleigh scattering)
3. Z is uniform throughout the contributing region
4. Multiple scattering is negligible

Question 16

What is Doppler principle?

Answer 16

Frequency of moving object shifts in response to movement of that object.

Question 17

What colors are inbound and outbound velocities?

Answer 17

Inbound- green

Outbound- red

Question 18

When is the full component of the wind measured? No component?

Answer 18

Full component when wind is parallel to radial, none is measured when perpendicular to radial

Question 19

What is an isodop?

Answer 19

Line of constant radial velocity

Question 20

What is the difference between base velocity and storm relative velocity?

Answer 20

Base velocity is raw data from radar, storm relative subtracts the movement of the storm from the base velocity

Question 21

How far is the range for reflectivity and velocity?

Answer 21

248nm in precip mode, 230 in clear air

Question 22

How many tilts for reflectivity and velocity?

Answer 22

4 in each mode

Question 23

What is the Doppler dilemma? How do we fix it?

Answer 23

There is no single PRF that maximizes both Rmax and Vmax. We use a dual PRF scanning strategy to avoid situation

Question 24

What are the sources of spectrum width?

Answer 24

Mean radial velocity estimate due to: wind shear and turbulence

Question 25

What is high and low spectrum width?

Answer 25

High- suggest turbulent flow such as boundaries and tornados

Low- suggest smooth flow such as RFDs and inflow