METEOROLOGY.pdf

METEOROLOGY Why is studying the weather important? Overview 1. Atmosphere 2. Heat Exchange Process 3. Global Circulation Patterns 4. Pressure Systems 5. Clouds 6. Thunderstorms 7. Frontal Systems 8. Weather Information Atmosphere ➢ Surrounds the Earth ➢ Held together by Gravity ➢ Mixture of gases ➢...

METEOROLOGY Why is studying the weather important? Overview 1. Atmosphere 2. Heat Exchange Process 3. Global Circulation Patterns 4. Pressure Systems 5. Clouds 6. Thunderstorms 7. Frontal Systems 8. Weather Information Atmosphere ➢ Surrounds the Earth ➢ Held together by Gravity ➢ Mixture of gases ➢ Medium in which we fly Layers of the Atmosphere Divided into layers based on temperature 1. Troposphere 2. Stratosphere 3. Mesosphere 4. Thermosphere 1. Troposphere o Ground level to 6mi / 33,000ft. o temperature decreases with height to -59deg. Celsius o Troposphere contains almost all the water vapor o Clouds and weather exist here o Vertical movement of air – warm air rising and cool air descending 2. Stratosphere o Tropopause to 160,000ft. o Relatively calm o Dry and clouds are rare o Temperature decreases to 0deg. o Location of the ozone layer – blocks sun’s harmful rays Properties of the Atmosphere - Density - Pressure - Humidity - Temperature 1 METEOROLOGY Density • Mass of air molecules in a given volume • Thickness of air Pressure • Force exerted by the weight of air molecules Temperature • Coldness or warmness of the air • Low = high pressure & density • High = low pressure & density Humidity • Amount of water vapor in the air • Water Vapor > Air molecules = Less Dense Air DENSITY PRESSURE TEMPERATURE Latent Heat INTERNATIONAL STANDARD ATMOSPHERE (ISA) Air is a perfectly dry gas Standard temperature at mean sea level: 15 °C Standard temperature lapse rate: 2°C per 1,000 ft. Standard pressure at mean sea level: 29.92 inHg Standard pressure lapse rate: 1 inHg per 1,000 feet. • Relative Humidity - how much water vapor is in the air compared to how much it can hold - reduce during the day and increase at night • Saturated Air – air that contains the maximum amount to water vapor it can hold • Unsaturated Air – air that is not holding as much water vapor as possible • Dew Point - temperature to which air must be cooled to become saturated with water vapor • Spread – difference between temp. & dew point Adiabatic Cooling Process • The process by which air cools 1. Parcel of air is heated 2. Expands 3. Density decreases 4. Weight decreases 5. Rises 2 METEOROLOGY Heat Exchange Process The Sun • Main source of energy on Earth Heat Exchange & Temperature Variation • Results in changes in weather Surface Heating & Cooling 1. Tilt of the Earth 2. Shape of the Earth 3. Land vs. Water 4. Cloud Cover Effects of Temperature • Buoyancy of Air Hot Air: Less Dense & Rises Cold Air: More Dense & Sinks • Pressure Pressure Gradient Force (PGF) - force that initiates wind • Wind - movement of air Advection: Horizontal Movement Convection: Vertical Movement 3 METEOROLOGY Wind Patterns 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 4 METEOROLOGY 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 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 5 METEOROLOGY CLOUDS Requirements for Formation • Humidity • Lifting Action - Instability - Convection - Orographic Lifting • Condensation Nuclei - Dust - 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 6 METEOROLOGY 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 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 7 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 8 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 9 METEOROLOGY FRONTAL SYSTEM - The boundary between two air masses with different characteristics *Air Mass – Large body of air with relatively the same characteristic Formation of Fronts • Frontogenesis – Birth of a front – When 2 airmasses meet • Frontolysis – Death of a front – Differing characteristics reconcile and breaks apart Types of Front • Warm Front • Cold Front • Stationary Front • Occluded Front 1. Warm Fronts • Warm air replacing cold air • Low Speed • Very Large Area • Stable Air • Drizzles • Stratus Clouds • Shallow Slope 2. Cold Front • Cold beats warm air • High Speeds • Small Area • Steep Slope • Associated with Cumulonimbus Clouds 3. Stationary Front • Two fronts of the same strength meet each other • Very slow/stationary • Bad weather may exist for several days 4. Occluded Front • One front overtaking the other • Both fronts are displayed • Thunderstorms exist • Stratus Clous may be visible 10 METEOROLOGY WEATHER INFORMATION 1. Metars 2. TAF 3. ATIS 4. Pireps 5. Sigmet 6. Airmet 7. Other Sources: FOBS, FSS 1. Metars • Meteorological Aerodrome Report • Produced every hour • Valid for 2 hours RPLC 060500Z 18006KT 9000 SCT020 BKN100 33/25 Q1008 NOSIG RMK A2977 RPLC 060500Z 18006KT 9000 SCT020 BKN100 33/25 Q1008 NOSIG RMK A2977 • Name of the airport • ICAO code • Day of the month & Time in Zulu – Zulu Time/UTC/GMT– primary time standard by which the world regulates clocks & time – Philippines GMT +8 • Wind direction & velocity • Visibility • Unit: Meters Factors Affecting Visibility • Clouds • Haze • Fog - Advection Fog - Radiation Fog • Cloud Cover • Temperature & Dew point • Altimeter Setting • QNH • Remarks 11 METEOROLOGY 2. Termina Area Forecast (TAF) • Terminal Aerodrome Forecast • Valid for 24 -30 hours • Updated every 6 hours TAF RPLC 060500Z 0606/0712 20006KT 7000 SCT020 BKN100 TX32/0606Z TN24/0621Z TEMPO 0606/0612 18008KT 5000 TS -SHRA FEW015CB SCT020 OVC100 12 METEOROLOGY 3. Automated Terminal Information Service ATIS • Pre-recorded weather information in high activity airports • Available on specific radio frequency • RPLC ATIS 127.20MHz 4. Pireps • Pilots Report • Actual weather at a specific time and place “adress, ident, position, altitude, operations (normal/abnormal) and prieps Pireps includes visibility, cloud ceiling, severe wx updates, approximate w/v” 5. Airmet and Sigmet • Airmet – Airmen Meteorological Information (Hazards to Light Aircraft) • Sigmet – Significant Meteorological information (hazards to all aircraft) • Inflight information given to all pilots (VFR and IFR) 6. Pre flight Meteorology • Accuweather.com – Print out: • Weather at point of origin • Weather at one way point en-route • Weather at destination – Attach all weather information to nav log – Submit nav log at the end of your flight • Understand the weather which is forecast • Use all the information available to you • Understand the weather you will be flying in • Make good judgements 13