Locking in for METR 122 Exam 2

Cirrus

• Wisps of delicate ice crystals

• No affect of air craft

Cirrocumulus

• Sheet of ice crystals and SCD

• Ripples in their pattern

• Some turb. and little icing

Cirrostratus

• Veil of ice crystals

• Produce halo around sun/moon

• No effect on aircraft

Altocumulus

• White/gray cloud w rounded masses

• Mostly liquid + SCD

• Some turb. + small icing

Lenticular

• White/Gray orographic cloud

• Form on wave crests of mountains/hills

• Some turb.

Altostratus

• Gray sheet cloud

• Ice crystals, SCD, + liquid droplets

• Little turb. w light-moderate icing

Cumulus

• Dense masses of white w defined edges

• Mostly liquid w some SCD

• Brief precip is possible

• Some turb. w no icing

Towering Cumulus

• Cumulus cloud with vertical development

• resemble cauliflower

• First stage of Tstorm development

• Strong turb. w some icing

Stratocumulus

• Gray/White rounded, flat-top

• Orderly groups or lines

• Small liquid and SCD

• Some turb. + possible icing

Stratus

• Gray sheet w uniform base

• Drizzle or some snow flurries

• Liquid, SCD, + ice crystals

• Little/no turb. w sign. icing

Nimbostratus

• Dark gray sheet cloud w precip

• Liquid, SCD, + ice crystals

• Thousands of ft. thick

• No lightning, hail, or thunder

• Low bases

• Little turb. + sign. icing

Cumulonimbus

• Dense vertically developed clouds

• Individual or lined up

• Top can hit stratosphere and spread out like anvil

• Heavy precip. w lighting, thunder, + hail

• Extreme turb., sign. icing, wind shear, and microbursts

What are the three types of high clouds?

Cirrus

Cirrocumulus

Cirrostratus

What are the three types of middle clouds?

Lenticular

Altostratus

Altocumulus

What are the types of low clouds?

Cumulus

Towering Cumulus

Nimbostratus

Cumulonimbus

Stratus

Stratocumulus

What are the eight types of precipitation?

Rain

Sleet

Snow

Hail

Freezing Rain

Graupel

Drizzle

Snow Grains

What is the Vertical Profile of Rain?

• Deep warm layer

• In winter: starts as snow and melts

• In summer: rain from top to bottom

What is the Vertical Profile of Snow?

• Below freezing layer all the way through

  • Size depends on T and saturation VP

What is the Vertical Profile of Freezing Rain?

• Deep warm aloft and shallow cold at surface

  • Snowflake melts and refreezes on contact

  • Cold, warm, cold

What is the Vertical Profile of Sleet?

• Shallow warm aloft and deep cold at surface

  • Cold, warm, cold

Main Types of US Air Masses?

• cA

• cP

• cT

• mT

• mP

Characteristics of cA air masses?

• very cold, very dry

• not seen in the summer

Characteristics of cP air masses?

• cold, dry

• Cold air outbreaks and lake-effect snow

Characteristics of cT air masses?

• hot, dry

• not in winter

Characteristics of mP air masses?

• cool, moist

Characteristics of mT air masses?

• warm, moist

• air mass Tstorms

How to locate a front?

Look for:

1. sharp T changes over short distance

2. changes in moisture content (DP)

3. shifts in wind direction

4. LP troughs + P changes

5. clouds + precip patterns

Characteristics of Cold Fronts?

• Cold air replacing warm

  • Steep slope of cold forces warm, moist air to rise

  • Cumulonimbus clouds common along front

  • Narrow band of heavy precip

  • Fast moving

  • Skies clear after frontal passage

Characteristics of Warm Fronts?

• Warm air replacing cold

  • Gentle warm slope forces warm, most air to rise over cold air

  • Nimbostratus clouds

  • Long-lasting, light precip

  • Slow moving

  • Precip on cold side

  • Low visibility

Characteristics of Stationary Fronts?

• Neither air mass is moving

  • Might produce precip

  • Light precip

  • Cold fronts become stationary near the Gulf

  • Secondary L might form

Characteristics of Occluded Fronts?

• Cold front lifts warm

  • cP on west - mP on east - mT aloft

  • Heavy long-lasting precip (slow)

  • Heaviest snow falls north of occlusion

  • End of storm system

Characteristics of Drylines?

• Low boundary separating cT + mT, often seen over southern Plains

  • Occurs in Spring + Summer

  • Can be a focal point for severe Tstorms

What does Cyclogenesis need to occur?

1. A frontal boundary between air masses of different characteristics

2. Area of divergence in the upper atmosphere

1st Step of Cyclogenesis

Stationary front w cold air N and warm S

• Winds are parallel to front in opposing directions

• Stationary front is common but can occur with cold fronts

2nd Step of Cyclogenesis

LP wave forms along front from opposing winds

• Circulation forces warm, moist to N and E + cool, dry to S and W

• Represents cold + warm frontal development

3rd Step of Cyclogenesis

Wave cyclone intensifies + fronts become more pronounced

• Precip strengthens N of warm front and along cold front with heavy precip surrounding L

• Cold front moves fast, warm slow

4th Step of Cyclogenesis

Cold front overtakes slow warm front + occlusion occurs

• Develops close to L + moves southward

• LP is deepest atp

• Heavy, long-lasting precip at occlusion

5th Step of Cyclogenesis

Occlusion ^^ + eventually cuts off mT air at surface

• Lack of warm, moist air causes P to rise, which weakens storm

Effects of High Pressure Systems on Aircraft?

• HP = less turb.

• Also means rapid cooling of Earth’s surface, so morning ground fog or frost can occur on an aircraft’s surface

Effects of Low Pressure Systems on Aircraft?

• Can cause turb., clouds, and precip

• Dangerous conditions of icing and Tstorms

What is turbulence?

Irregular motion of an aircraft in flight caused by rapid variation in wind velocities.

What are the three types of turbulence?

1. Convective Turbulence (and Dry Convection)

2. Mechanical Turbulence

3. Wind Shear

What is Convective Turbulence?

Vertical motions caused by convective currents.

How are Convective Currents created?

• Heated air at the surface creates a shallow absolutely unstable layer

• Convection ^^ in strength and height as surface heating increases

How do pilots avoid convective currents?

Flying above cumulus clouds

What cloud type do convective currents create?

Cumulus

What is Mechanical Turbulence?

Disruptions to airflow from obstructions (e.g. Trees, Buildings, and Mountains)

• Intensity depends on wind speed and surface roughness

• Eddies flow downstream

How to mountains create Mechanical Turbulence?

Stable air flows over a mountain/ridge and produces severe/extreme turbulence.

• Downdrafts can exceed max climb rate and make an aircraft crash

What type of cloud does Mechanical Turbulence create?

Lenticular Clouds form in the rising branches of waves from mountain Mechanical Turbulence.

What is Wind Shear Turbulence?

Turbulence from the rate of change of wind direction/speed

• Strong wind shears occur at T inversion layers

What is Clear Air Turbulence?

High-altitude turbulence occurring in cloud-free regions near jet streaks.

• 20,000-50,000 ft.

• Affects aircraft w/o warning

• Intensity is greater in the winter

What does an aircraft’s response to turbulence depend on?

1. Intensity

2. Aircraft Size

3. Wing Loading

4. Airspeed

5. Aircraft Altitude

What are adverse winds?

A category of hazardous weather responsible for weather related accidents:

1. Crosswinds

2. Gusts

3. Tailwind

4. Variable Wind

5. Sudden Wind Shifts

• Takeoff and Landing are most susceptible

What are crosswinds?

Winds with a component directly perpendicular to the heading of an aircraft.

• If not accounted for: aircraft drifts off the runway or landing gear fails

What are wind gusts?

Gusts are a fluctuation of wind speed with variations of 10 kts or more.

• Gusts = ^^ airspeed = ^^ lift

• Sudden ending of a gust = sinking aircraft

What is a tailwind?

Wind with a component behind aircraft

• Hazardous during takeoff AND landing

• ^^ groundspeed = sufficient lift = longer takeoff roll (in turn creates a longer landing roll too)

• A small initial climb gradient means the aircraft might not avoid obstacles at the end of the runway

What are variable winds and sudden wind shifts?

Winds changing directions frequently

What is wind shear?

Change in wind speed/direction in the vertical

How does icing occur?

Icing occurs when pilots pass through clouds and precipitation composed of SCD.

What is the main impact icing has on aviation?

It destroys the smooth airflow and ^^ drag while __ lift.

What are the three types of structural icing?

1. Rime Icing

2. Clear Icing

3. Mixed Icing

What is Rime Icing?

Rough, milky ice formed by slow SLD

• Most frequently reported

• Grows on edges of aircraft

• Forms:

  • Colder Ts

  • Lower liquid water content

  • Small droplets

What is Clear Icing?

Translucent ice formed by slow freezing SLD

• Small droplets freeze and spreads over aircraft’s surface to refreeze

• More hazardous than rime icing

  • More turbulent airflow

  • Can spread out of deicing range

• Forms:

  • Warmer Ts

  • Higher liquid water content

  • Larger droplets

What is Mixed Icing?

Mix of clear and rime icing

• Same hazards as clear icing

• Forms when aircraft moves thru clouds with varying T, liquid water content, and droplets

What type of icing occurs in Stratiform clouds?

Rime or Mixed

• Confined to 3-4k ft.

• Trace to light icing

• Max icing occurs in upper cloud

What type of icing occurs in Cumuliform clouds?

Clear or Mixed

• Icing layer is small horizontally but greater vertically

• Intensity varies + depends on cloud’s vertical development

• Max icing in upper cloud

What are some icing hazards?

1. Destroys smooth airflow and ^^ drag, which __ lift

2. Weight of ice is less important

3. As power ^^ for drag ^^, AOA must be lifted to maintain altitude

   1. leads to ice under wings and fuselage

How do light aircrafts get affect from icing?

• Moderate to Severe icing causes stalling at high speeds and lower AOAs

• They can roll and pitch w little recovery