AMS Study Guide - Radar Meteorology

Radar Meteorology

What is the WSR-88D?

Stands for Weather Surveillance Radar 88 Doppler

What is the difference between a Doppler Radar and a Dual-Polarization radar?

The Doppler only emits a horizontal signal. Dual Polarization Radar emits a vertical and horizontal pulse to give a better idea of the side of a hydrometer or object the radar beam hits

How often does the radar scan?

Every 4-6 minutes

What do the red and green color son the radars velocity product indicate?

Red shows winds that are going away from the radar, green shows winds going towards the radar site

Base Velocity helps to better detect ________, while storm Relative Velocity helps us to detect _______.

Straight Line Winds; Rotation or Tornadic activity

What is virga?

When we have rain in the upper levels of the atmosphere, but dry air at the surface. Essentially the rain evaporates before it even reaches the ground due to the dry air in place in the atmosphere

What are the advantages and disadvantages of Clear Air Mode with a Radar?

It is very sensitive, but much slower as a result

What are the advantages and disadvantages of Precipitation Mode with a Radar?

It is less sensitive, but much faster

How large is a hydrometer to the radar?

6

What is the “Zero Zone”?

Where the winds are perpendicular to the radar, and the radar velocity is zero

Also known as Zero Isodop

True or False: The resolution of the radar decreases when the distance increases

True

If the radar beam is 1 degree, can it pick up a tornado signature at 120 nm?

No

What is the average Radar Beam?

95 degrees

The Average radar beam can only pick up detailed structures, such as tornadoes, at what distance?

Within 48 nm

If a radar beam is at 0.5-degree tilt, at 120 nm, how far above the ground is the beam?

10,000 to 15,000 feet

Ground clutter picked up by the radar beam may be: Birds, Bugs, Traffic, Building or all of the above

All of the Above

What does red indicate in the velocity product of radar?

Winds moving away from the radar sight

True or False: Radar can detect precise precipitation amounts or Flash Flooding?

False

If rain hits the radome, what does it do: Increases Sensitivity, Decreases sensitivity, or Disrupts the Scan?

Decreases Sensitivity

What is the definition of Velocity Aliasing?

AKA Velocity Folding

Happens when the radar can not measure speeds above a certain limit, so it “wraps” or “folds” the velocity values in the wrong direction or to a lower value.

What is the dispersion of Velocities within the radar sample volume called?

Spectrum Width

Can be used to detect tornado vortex signatures

When the unambiguous range increases, the PRF of the radar (Increases or Decreases)?

Decreases

How can you identify 1 inch + hail on radar?

Three Scale Body

What is the Doppler Dilemma?

Deals with Range vs Velocity with Pulse Frequency (PRF)

LOW PRF means you have a high range, but low velocity

HIGH PRF means you have low range, but high velocity

What is the Marshall Palmer Relationship?

The Relationship between Reflectivity and Rainfall Rate

True or False: A microburst will show divergence on radar

True

How can you identify Divergence (Cyclonic) on Radar?

Winds moving away from radar (red) and towards the radar (green) create a counter clockwise or cyclonic rotation

How can you identify Convergence (Anti-cyclonic) on radar?

Winds moving away from the radar (red) and towards the radar (green) create a clockwise or anti-cyclonic rotation

What is the “Cone of Silence”?

The area directly above the radar

Happens because the radar beam can not extend vertically in the atmosphere, so we have little idea as to what is occurring directly over the radar site.

What is the X-Band on Radar?

They are Sub-bands used by Military, Government & Civil Institutions for Weather Monitoring, Defense Tracking and Speed Detection

Identify this radar Signature:

Hail Core

Looking for high reflectivity values (pink or purple) located in the main body of a thunderstorm

Identify this radar Signature:

Forward Flank

Positioned on the leading edge of the storm. Look for moderately high reflectivity (green and yellow) expecting from the core of the main storm

Identify this radar Signature:

Rear Flank

A clear spot or weak echo region on the backside of the storm. Located at the rear. It curves around the back of the storm forming a “hook” with heavy precipitation to the east.

Identify this radar Signature:

Flanking Line

Look for lower reflectivity values (green to yellow) indicating a line of developing cells. Positioned to the southwest of a main supercell. Looking for a linear or stair-step structure of smaller, developing cumulus clouds.

Identify this radar Signature:

Bounded Weak Echo Region

A weak echo region surrounded by high reflectivity. Typically found near the center of a strong thunderstorm of supercell

A donut or hole-like appearance within intense reflectivity, indicating a strong updraft

Identify this radar Signature:

Hook Echo

A distinctive, curved or hook-like structure extended from the main storm body. A spiral or “comma” shape, often pointing towards the rear of the storm

Identify this radar Signature:

V notch or “Flying Eagle”

Strong upper-level winds moving moisture downwind, producing a V shape as precipitation goes outwards on radar

A clear “V’ or wedge shape, indicating strong upper-level divergence

Identify this radar Signature:

Diverging Flow Updraft

Opposing wind directions, typically in the mid-levels of a storm. Look for a clear split in wind directions with a strong gradient

Identify this radar Signature:

Bow Echo

A bow-shaped or arced band of high reflectivity

Identify this radar Signature:

Debris Ball (NEED TO ADD IMAGE)

Extremely high reflectivity (usually pink, purple or white) within the hook echo or a tornadic storm