DGCA ATPL Aviation Meteorology study guide
DGCA ATPL Aviation Meteorology · Work through your exam, one topic at a time.
Aviation Meteorology is one of the knowledge areas a candidate must pass to hold a Commercial or Airline Transport Pilot Licence under the Indian Directorate General of Civil Aviation. It is written for student pilots, licence holders adding a rating or converting a foreign licence, and instructors who need a current meteorological knowledge base. The DGCA ATPL Aviation Meteorology study guide has 10 sections and about 2,998 words.
01The Atmosphere: Composition, Vertical Structure and Standard Atmosphere
The atmosphere is a mechanical mixture of gases, not a chemical compound: roughly 78% nitrogen, 21% oxygen, 0.93% argon and 0.04% carbon dioxide by volume, with water vapour variable from near zero to about 4%. Candidates must know that water vapour and aerosols are the variable constituents, and that ozone concentrates in the stratosphere where it absorbs ultraviolet radiation and produces the inversion that caps the troposphere.
307 words, about 2 min02Temperature, Pressure, Density and the Gas Laws
Temperature is a measure of mean molecular kinetic energy. Candidates should be fluent in Celsius, Kelvin and Fahrenheit conversion (K = °C + 273.15) and in the meaning of dry adiabatic lapse rate (DALR ≈ 3 °C/1000 ft), saturated adiabatic lapse rate (SALR, variable, roughly 1.5–2 °C/1000 ft in warm moist air) and environmental lapse rate (ELR).
299 words, about 1 min03Atmospheric Pressure, Altimetry and Pressure Systems
Atmospheric pressure is the weight of the column of air above a surface, measured in hPa (mb), inches of mercury or, in some states, mm Hg. Standard sea-level pressure is 1013.25 hPa.
310 words, about 2 min04Water Vapour, Humidity, Condensation and Stability
Water vapour enters the air by evaporation and leaves it by condensation; the maximum mass it can hold rises steeply with temperature (roughly doubling for every 10 °C). Candidates must distinguish mixing ratio and specific humidity (mass-based, little changed by compression) from relative humidity (ratio of actual to saturation vapour pressure, changes with temperature) and from dew point and frost point.
276 words, about 1 min05Clouds, Precipitation and Fog
Clouds are classified by height and form: high (cirrus, cirrostratus, cirrocumulus), middle (altostratus, altocumulus), low (stratus, stratocumulus, nimbostratus) and clouds of vertical development (cumulus, cumulonimbus). Candidates must link cloud type to stability and to the associated weather: stratiform cloud means stable air and steady, often light precipitation; cumuliform cloud means instability, showers and turbulence.
285 words, about 1 min06Air Masses, Fronts and Frontal Weather
Air masses are classified by origin and track: continental or maritime, tropical, polar or arctic. As an air mass moves it is modified by the underlying surface.
286 words, about 1 min07Synoptic Meteorology, Pressure Patterns and the Indian Monsoon
Synoptic charts show isobars, fronts, pressure centres and troughs. Candidates must interpret pressure systems: a depression (low) has converging cyclonic flow with rising air, cloud and precipitation; an anticyclone has diverging anticyclonic flow with subsidence, clear skies and often haze or fog beneath an inversion.
306 words, about 2 min08Thunderstorms, Turbulence, Icing and Other Hazardous Weather
A thunderstorm needs three ingredients: sufficient moisture, conditional instability and a lifting trigger (heating, front, orography or convergence). Its life cycle has three stages: cumulus (updraughts only), mature (updraughts and downdraughts, heaviest rain, hail, lightning, maximum turbulence and icing) and dissipating (downdraughts dominate).
322 words, about 2 min09Meteorological Observations, Reports, Forecasts and Charts (METAR, TAF, SIGMET, etc.)
Candidates must decode coded reports fluently. METAR is a routine aerodrome observation, usually issued hourly; SPECI is a special report issued when significant change occurs.
304 words, about 2 min10Climatology and Aviation Weather Services
Climatology examines average and extreme weather over time and the seasonal patterns that affect flight planning. Candidates should know the global circulation: Hadley, Ferrel and Polar cells; the trade winds, westerlies and polar easterlies; the ITCZ and subtropical highs; and the semi-permanent pressure centres (Azores, Siberian, Icelandic, Aleutian).
303 words, about 2 min