2 METEOROLOGY.pdf

METEOROLOGY Global Circulation Patterns - Heat is transported around the Earth in convection Global Circulation Patterns • Equatorial Cell 0°-30 ° latitude • Mid Latitude Cell 30°- 60° latitude • Polar Cell 60° - 90° latitude Coriolis Effect - effect of rotation of the Earth on wind movement (The C...

METEOROLOGY Global Circulation Patterns - Heat is transported around the Earth in convection Global Circulation Patterns • Equatorial Cell 0°-30 ° latitude • Mid Latitude Cell 30°- 60° latitude • Polar Cell 60° - 90° latitude Coriolis Effect - effect of rotation of the Earth on wind movement (The Coriolis effect is a phenomenon that occurs due to the rotation of the Earth. It causes moving air or water to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere) (google) Surface Friction Layer - Flow of wind from ground level to 2,000ft. - Obstacles on Earth Pressure System - Areas with uniformly levels of Pressure Two Types: - Low pressure Area - High pressure Area High Pressure Area Cloud: Less/None Precipitation: None Wind: Light Visibility: Possibly Hazy Low Pressure Area Cloud: Broken/Overcast Precipitation: Light to heavy Wind: Strong Visibility: Poor in precipitation 1 METEOROLOGY Direction of Wind Flow • North Hemisphere: – High Pressure Areas: CLOCKWISE/ANTI-CYCLONIC – Low Pressure Areas: COUNTERCLOCKWISE / CYCLONIC • South Hemisphere – High Pressure Areas: COUNTERCLOCKWISE – Low Pressure Areas: CLOCKWISE Isobars - connects areas with equal pressure *Closer isobars = stronger winds/pressure gradients *PGF - force which makes high pressure go to low pressure *Coriolis Force - prevents air to flow directly from high pressure to low pressure area Ridge – elongated area of high pressure Trough – elongated area of low pressure CLOUDS Requirements for Formation • Humidity • Lifting Action - Instability - Convection - Orographic Lifting • Condensation Nuclei - Dust 2 METEOROLOGY - Pollen - Dirt - Salt Cloud Formation 1. Moist Air is lifted 2. Air is cooled – dewpoint reached 3. Air is saturated 4. Water Vapor condenses into water droplets Types of Clouds by Appearance Families of Clouds What Clouds Will Form? Stability – how the atmosphere will react when there is vertical motion of air • Stable Air – Resists vertical movement – Flat clouds • Unstable Air – Prone to vertical movements – Rising clouds Stable Air • Stratus type cloud • Steady Precipitation • Steady winds • Smooth flying conditions • Poor low-level visibility Unstable Air • Cumulus Clouds • Showery precipitation • Gusty winds • Turbulence may be moderate to severe • Good visibility 3 METEOROLOGY THUNDERSTORMS “One or more cumulonimbus clouds accompanied by sudden electrical discharges called lightning, which cause a sound called thunder” How do you know if it’s a thunderstorm? ✓ Large cumuliform type clouds ✓ Dark colored ✓ Rain bearing ✓ Lightning ✓ Thunder Requirements for a Thunderstorm • Humidity • Instability • Lifting Action 2 Types: > Airmass – lifting due to local convection > Frontal – Lifting due to frontal activity (when warm & cold air meet) • Condensation Nuclei Life Stages of a Thunderstorm 4 METEOROLOGY Elements of a Thunderstorm 1. Precipitation 2. Icing 3. Hail 4. Microburst 5. Wind Shear 6. Turbulence 7. Lightning 8. Tornado 1. Precipitation - water released from the clouds - rain, snow, or hail 2. Icing - causes friction - may prevent the airplane from becoming airborne at normal take-off speed 3. Hail – Balls of ice – Solid Precipitation – Requirements: • Precipitation • Updrafts • Temperature below 0 deg. • Inside Clouds 4. Microburst – small scale, very intense downdrafts which descend to the surface and upon contact with the surface, diverge outwards in all directions. 5. Windshear - Wind shear is a change in wind speed and/or direction over a short distance - It can be present at any level and can exist in both a horizontal and vertical direction How to recognize? monitor the speed and proper power setting on approach 5 METEOROLOGY 6. Turbulence – irregular motion of the air resulting from eddies and vertical currents • Low Level Turbulence – due to surface heating and friction – Turbulence below 15,000 ft. • Mechanical Turbulence – results when airflow is hindered by surface friction or an obstruction • Convective Turbulence – Thermal turbulence – Produced by dry convection – Typically on day time – Cumulus forming • Wake Turbulence – Wake turbulence is somewhat more predictable since all aircraft generate lift, a requirement for wake turbulence – Air from below the wing is drawn around the wingtip into the region above the wing by the lower pressure above the wing, causing a vortex to trail from each wingtip. 7. Lightning – electrical discharge – Caused by colliding particles of rain, ice, or snow inside storm clouds increase the imbalance between storm clouds and the ground 8. Tornado – Narrow, violently rotating column of air – warm, humid air collides with cold, dry air – forms a condensation funnel made up of water droplets, dust and debris. Importance to Pilots! • Thunderstorms last only 45mins. to 1 hour • There may be multiple thunderstorms in an area at different stages • Find an alternate route! Do not wait it out • Know where the storm is going • Options: - Fly Around - Land Before the storm - Make a U-turn 6