Weather Flashcards
What is met?
Meteorology is the study of the behaviour and composition of the atmosphere.
ISA?
Pressure 1013.25Hpa Temp 15 deg celsius at MSL Temp decline 1.98 deg/1000feet Air density 1.225kg/m3 Gravity 9.8ms2
What is weather?
State of the atmosphere within a given region at a given point in time. Described via Temperature, Pressure and presence of features such as wind, moisture, and cloud.
Key weather measures
Pressure, Density, Temp, Stability
High pressure at surface
Mass subsidence
Air sinking
Anti-cyclonic fast moving winds, clear skies, stable conditions
Low pressure at surface
Air rising at surface
Cyclonis slow moving winds, cloudy skies, stable atmospheric conditions
Stable Air
If stable that volume will resist any attempt to displace it or will, once displaced, cease moving or return to its starting point.
Unstable air
If a volume of air is unstable and is displace i.e. moved away from its starting point or acted upon by some external force it will continue to move
Layers of the atmosphere?
Troposphere, Stratosphere
Mesosphere, thermosphere
Major components of atmosphere?
78% Nitrogen
21% Oxygen
Why is water in the atmosphere important?
The constant movement between states either releases energy into or takes energy out of the surrounding atmosphere in the form of latent heat which in turn cools down or warms up that atmosphere altering its behaviour.
What drives the world weather?
Driven by energy from the Sun or Solar Radiation.
Reasons for solar variation?
driven by energy from the Sun or Solar Radiation.
Three types of icing?
Clear, rime & hoar frost
What determines type and severity of icing?
Amount of super cooled water, air temp, size o droplets
Dangers of aircraft icing?
Increased drag.
Distortion of aircrafts aerodynamic shape.
Increase in stall speed.
Loss of thrust.
Blocked Pitot & Static Tubes and/or Carburettor intakes.
Broken aerials.
Loss of control over control surfaces.
What is clear ice?
Translucent sheets of ice that form when droplets freeze slowly when hitting an aircraft.
What is rime ice?
Brittle, opaque, milky ice that forms when water hits an aircraft and freezes extremely quickly.
Hoar frost?
When water goes straight from gas frozen state.
Anti & De-icing methods
Mechanical - pneumatic boots
Fluid - liquid like glycol sprayed to prevent
Thermal - heating with elements or hot air
What is turbulence?
Persistent agitation in air flow
Intensity is determined by impact on aircraft
Causes - convective currents, obstructions, wind shear
Microbursts?
Columns of rapidly descending air found in powerful Cb clouds. Hazards include - Strong downdrafts up to 7,000 ft/min. Wind shear turbulence. Gust front & vortex ring.
Thunderstorm?
A Cb cloud with one or more electrical discharges manifested by lightning & thunder.
Hazards - Heavy precipitation, hail, ice, turbulence, lightning
Mountain Waves?
Laminar wind flow patterns associated with large mountains or mountain ranges. Hazards: Wind shear & Turbulence. Rotor Zones. Downdrafts.
Beaufort scale?
It depicts the force of wind by a series of numbers from 0 to 12.
A scale of wind speed based on a visual estimation of the wind’s effects
WHat is hail?
Hail is a form of precipitation that occurs when updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere where they freeze into balls of ice.
How do hailstones grow?
Hailstones grow by colliding with supercooled water drops. Supercooled water will freeze on contact with ice crystals, frozen raindrops, dust or some other nuclei. Thunderstorms that have a strong updraft keep lifting the hailstones up to the top of the cloud where they encounter more supercooled water and continue to grow. The hail falls when the thunderstorm’s updraft can no longer support the weight of the ice or the updraft weakens. The stronger the updraft the larger the hailstone can grow.
How does a thunderstorm form?
3 ingredients - moisture, rising unstable air, lifiting mechanism
Stages - Developing, mature, dissipating
What is a super cell thunderstorm?
The supercell, characterised by
a single rotating updraft reaching great vertical extent
Requires strong vertical wind shear, strong instability and large moisture
supply
Difference between cyclone, hurricane, typhoons?
Depends only on which ocean they are formed from.
Hurricanes -North Atlantic Ocean and Northeast Pacific
Cyclones - South Pacific and Indian Ocean
Typhoons - Northwest Pacific Ocean
