WX 201 Exam 3 Study Guide with complete
solutions
What is a cloud?
a volume of atmosphere containing numerous water droplets and/or ice particles
What ingredients are necessary for cloud development?
-Abundant water vapor
-Condensation nuclei particles
-A cooling mechanism
What is supercooled water? At what temperature does it exist, and how does it freeze?
Cloud drops that remain liquid down to -40 degrees Celcius. May freeze when the temperature
decreases, encounters an ice nucleus, or collides with a solid object
What are the types of fog?
Radiation fog(Ground fog), advection fog, steam fog(Mixing fog), and upslope fog
What are the two basic types of clouds?
cumuliform and stratiform
What are some visual properties of clouds?
Fall Streaks: Lines extending downward from base of cloud, indicating precipitation
Boundaries: water clouds have distinct edges; ice clouds usually appear bumpy
Color: dark cloud base has deep vertical extent
Between what height ranges are clouds considered low, middle, or high?
Low: (Base<6,500 ft AGL)
Middle: (Base 6,500 - 20,000 ft AGL)
High: (Base >20,000 ft AGL)
Know these clouds:
Cirrus, cirrostratus, cirrocumulus, altostratus, cumulonimbus, cumulus, stratus, stratocumulus,
nimbostratus.
What types of satellite imagery are there?
Visible imagery, infrared imagery, and water vapor imagery
How is visible imagery used?
Detects reflected or scattered sunlight. Indicates cloud shape, texture and opacity. Time loops reveal
trends and airflow.
How is infrared imagery used?
Depicts infrared radiation from clouds and surfaces.
How is water vapor imagery used?
, Detects IR Wavelength (6.7 Micrometers) emitted by water vapor
How does radar work?
The transmitter emits pulses of microwaves, a type of radio waves, outward in a circular pattern.
Precipitation scatters these microwaves, sending some energy back to the transmitter, where it is
detected by the radar's receiver.
What approximate reflectivity ranges (in dBZ) correspond to light, moderate, and heavy rain?
Light: 0.01-0.17
Moderate: 0.17-0.5
Heavy: 0.5-2.0
What causes attenuation?
When observing strong echoes (heavy precipitation) with some radars
What is the difference between base reflectivity and composite reflectivity and which is better to use
for aircraft navigation?
Composite reflectivity reveals echos at higher altitudes and is more accurate and reliable. Use
composite
What is the difference between stratiform and and convective echoes?
Convective are more stronger and dangerous for flight. Convective is typically identified on radar by
red yellow or even pink/purple
What do severe weather echo patterns look like?
Echoes that are not circular. (Bow, finger, and hook shaped)
What does radial velocity from a doppler radar indicate?
Speed of precipitation particles toward or away from the radar antenna
What are the requirements for cloud formation?
Water vapor, cloud condensation nuclei, and a cooling mechanism
What is an additional requirement for cumulus cloud formation?
Conditional instability and a triggering mechanism
define conditional instability
the condition of moist air with an environmental lapse rate between the dry and wet adiabatic rates
define absolute stability
Occurs when with a layer:ELR < SALR < DALR
•Rising air will end up cooler than surroundings-regardless of whether it is saturated or unsaturated
•Buoyancy acts to restore parcels to initial altitute
define absolute instability
solutions
What is a cloud?
a volume of atmosphere containing numerous water droplets and/or ice particles
What ingredients are necessary for cloud development?
-Abundant water vapor
-Condensation nuclei particles
-A cooling mechanism
What is supercooled water? At what temperature does it exist, and how does it freeze?
Cloud drops that remain liquid down to -40 degrees Celcius. May freeze when the temperature
decreases, encounters an ice nucleus, or collides with a solid object
What are the types of fog?
Radiation fog(Ground fog), advection fog, steam fog(Mixing fog), and upslope fog
What are the two basic types of clouds?
cumuliform and stratiform
What are some visual properties of clouds?
Fall Streaks: Lines extending downward from base of cloud, indicating precipitation
Boundaries: water clouds have distinct edges; ice clouds usually appear bumpy
Color: dark cloud base has deep vertical extent
Between what height ranges are clouds considered low, middle, or high?
Low: (Base<6,500 ft AGL)
Middle: (Base 6,500 - 20,000 ft AGL)
High: (Base >20,000 ft AGL)
Know these clouds:
Cirrus, cirrostratus, cirrocumulus, altostratus, cumulonimbus, cumulus, stratus, stratocumulus,
nimbostratus.
What types of satellite imagery are there?
Visible imagery, infrared imagery, and water vapor imagery
How is visible imagery used?
Detects reflected or scattered sunlight. Indicates cloud shape, texture and opacity. Time loops reveal
trends and airflow.
How is infrared imagery used?
Depicts infrared radiation from clouds and surfaces.
How is water vapor imagery used?
, Detects IR Wavelength (6.7 Micrometers) emitted by water vapor
How does radar work?
The transmitter emits pulses of microwaves, a type of radio waves, outward in a circular pattern.
Precipitation scatters these microwaves, sending some energy back to the transmitter, where it is
detected by the radar's receiver.
What approximate reflectivity ranges (in dBZ) correspond to light, moderate, and heavy rain?
Light: 0.01-0.17
Moderate: 0.17-0.5
Heavy: 0.5-2.0
What causes attenuation?
When observing strong echoes (heavy precipitation) with some radars
What is the difference between base reflectivity and composite reflectivity and which is better to use
for aircraft navigation?
Composite reflectivity reveals echos at higher altitudes and is more accurate and reliable. Use
composite
What is the difference between stratiform and and convective echoes?
Convective are more stronger and dangerous for flight. Convective is typically identified on radar by
red yellow or even pink/purple
What do severe weather echo patterns look like?
Echoes that are not circular. (Bow, finger, and hook shaped)
What does radial velocity from a doppler radar indicate?
Speed of precipitation particles toward or away from the radar antenna
What are the requirements for cloud formation?
Water vapor, cloud condensation nuclei, and a cooling mechanism
What is an additional requirement for cumulus cloud formation?
Conditional instability and a triggering mechanism
define conditional instability
the condition of moist air with an environmental lapse rate between the dry and wet adiabatic rates
define absolute stability
Occurs when with a layer:ELR < SALR < DALR
•Rising air will end up cooler than surroundings-regardless of whether it is saturated or unsaturated
•Buoyancy acts to restore parcels to initial altitute
define absolute instability
