NAV Brasil Aeronautical Meteorologist cheat sheet

Hydrostatic equation: dp/dz = -ρg; integrated form p(z) = p0·exp(-z/H) with scale height H = RdT/g ≈ 8 km for T = 273 K.

First law of thermodynamics: dq = cpdT - αdp; for adiabatic processes dq = 0, giving the dry adiabatic lapse rate Γd = g/cp ≈ 9.8 K/km.

Potential temperature θ = T(p0/p)^(Rd/cp), with p0 = 1000 hPa and Rd/cp ≈ 0.286; θ is conserved in dry adiabatic motion.

Equivalent potential temperature θe is conserved in moist adiabatic processes and is used to identify air masses and conditional instability.

Clausius-Clapeyron: saturation vapor pressure grows about 6-7 percent per kelvin; es(T) ≈ 6.11 hPa at 0 °C.

Relative humidity RH = e/es × 100 percent; dew point Td is the temperature to which air must cool at constant pressure and moisture to reach saturation.

Lifting condensation level: zLCL ≈ 125 m per °C of dew-point depression (T - Td); the moist adiabatic lapse rate is about 5-6 K/km in warm air.

Conditional instability occurs when the environmental lapse rate lies between the moist and dry adiabatic rates; CAPE measures the buoyant energy released.

Coriolis parameter f = 2Ωsinφ; geostrophic wind ug = -(1/ρf)∂p/∂y, vg = (1/ρf)∂p/∂x, blowing parallel to height contours with low pressure to the left in the Southern Hemisphere to the right.

Quasi-geostrophic omega equation: ascent is forced by positive vorticity advection increasing with height and by warm advection; descent by the opposite.

Rossby wave speed c = U - βL²/(4π²); longer waves move more slowly and may retrogress when U is small.

Thermal wind: the geostrophic wind shear vector is parallel to the mean isotherms with cold air to the left in the Southern Hemisphere; shear magnitude grows with horizontal temperature gradient.

Vorticity ζ = ∂v/∂x - ∂u/∂y; absolute vorticity includes f; conservation of absolute vorticity explains lee troughing and ridge amplification.

Hypsometric relation links thickness between two pressure levels to mean virtual temperature: thicker layers mean warmer air.

Jet streak dynamics: ascent occurs in the left-exit and right-entrance quadrants, favoring surface cyclogenesis and convective development.

Ageostrophic flow is directed toward low pressure in regions of subgeostrophic wind, producing convergence and vertical motion.

Frontal types: cold fronts have steep slopes (1:50 to 1:100) and narrow bands; warm fronts slope about 1:150 to 1:200 with broad stratiform precipitation.

Squall lines and mesoscale convective systems produce gust fronts, heavy rain, hail, and low-level wind shear; they propagate faster than individual cells.

Sea breeze circulations form when land-sea temperature contrast exceeds about 2 K; they reach 20-50 km inland and can trigger thunderstorms.

Orographic lifting enhances rainfall on windward slopes and produces foehn/chinook warming and drying on lee slopes.

Tropical cyclones require sea-surface temperature above about 26.5 °C, weak vertical wind shear, and at least 5 degrees latitude from the equator for Coriolis forcing.

Extratropical cyclones follow the Norwegian model: warm sector, cold front, warm front, and occlusion as the cold front catches the warm front.

Low-level jets, such as the South American Low-Level Jet east of the Andes, transport moisture and favor nocturnal convection.

Cut-off lows and blocking highs are quasi-stationary systems that produce persistent weather and forecast difficulty.

Surface analysis uses mean sea level pressure reduced with the standard atmosphere; isobars are drawn at 4 hPa intervals on Brazilian charts.

Upper-air charts use geopotential height at standard levels (850, 700, 500, 250 hPa); 500 hPa troughs and ridges steer surface systems.

Skew-T log-p diagrams show temperature, dew point, and parcel paths; CAPE, CIN, and shear indices are read directly.

Convective forecast decision rule: CAPE above about 1000 J/kg with shear above 15 m/s supports organized severe storms.

Satellite and radar trends supplement model output; persistence plus climatology is a baseline forecast against which NWP is compared.

Model spread among ensemble members indicates forecast uncertainty; a tight cluster supports higher confidence.

Nowcasting relies on radar echo motion and satellite cloud-track winds for the 0-6 hour horizon.

Verification metrics include hit rate, false alarm ratio, and threat score; bias measures systematic over- or under-forecasting.

Low-level wind shear and microbursts are critical hazards in the takeoff and landing phases; microburst downdrafts can exceed 20 m/s and spread out over 1-4 km.

Icing occurs in supercooled water clouds between 0 °C and about -20 °C; severe icing is associated with freezing rain and large drop sizes.

Clear air turbulence is invisible to radar and occurs near jet streams, in mountain waves, and at tropopause folds.

Volcanic ash damages engines and windshields; SIGMETs are issued for ash, tropical cyclones, severe turbulence, icing, and sandstorms.

Thunderstorm criteria for significant weather: hail, surface wind gusts of 15 m/s or more, and cumulonimbus clouds.

Wind shear on final approach is reported as a warning when the headwind or tailwind changes by 15 kt or more.

Mountain wave turbulence is enhanced by winds above 15 m/s perpendicular to ridges and stable air aloft.

Runway visual range and ceiling determine low-visibility operations; CAT I minima are 200 ft decision height and 550 m RVR.

Aneroid barometers and barographs measure pressure; a mercury barometer reading must be corrected for temperature and gravity to obtain station pressure.

Radiosondes measure temperature, humidity, and pressure and derive wind from GPS or radar tracking; standard launch times are 0000 and 1200 UTC.

Anemometers: cup anemometers measure speed, vane anemometers measure direction; sonic anemometers measure both without moving parts.

Rain gauges: tipping bucket records intensity, weighing gauges measure accumulation; disdrometers classify drop size distributions.

Automatic weather stations transmit SYNOP, METAR, and SPECI reports through national and international networks.

Ceilometers measure cloud base by lidar backscatter; transmissometers and forward-scatter sensors estimate visibility.

Radar reflectivity factor Z is proportional to the sixth power of drop diameter; Z = 200R^1.6 is a typical Z-R relation.

Instrument error sources include siting exposure, radiation shielding, and calibration drift; regular calibration traceable to standards is required.

Geostationary satellites orbit at about 35,786 km altitude and view the same hemisphere continuously; polar orbiters at 800-900 km provide higher resolution and global coverage.

Visible imagery shows cloud albedo and is available only in daylight; infrared imagery measures cloud-top temperature day and night.

Water vapor channel (about 6.2 µm) shows upper-tropospheric moisture and jet stream structure.

Doppler radar measures radial velocity to detect rotation, convergence, and gust fronts; dual-polarization distinguishes rain, hail, and debris.

Brightness temperature from infrared channels is calibrated to blackbody radiation; cloud-top height is inferred from temperature.

Scatterometers measure ocean surface wind vectors; altimeters measure wave height; microwave sounders retrieve temperature and humidity profiles.

Satellite products include ASCAT winds, scatterometer sea state, and derived instability indices used in nowcasting.

Geostationary orbit requires an altitude where the orbital period equals Earth's rotation period of 23 h 56 min.

Primitive equations include momentum, continuity, thermodynamic, moisture, and equation of state; they are solved on a grid with time stepping.

Grid spacing determines resolvable scales; features smaller than about 4-7 grid lengths are not resolved and require parameterization.

Parameterizations include convection, boundary-layer turbulence, radiation, cloud microphysics, and land-surface processes.

Data assimilation combines observations with a background field using weights from background and observation error covariances; 3D-Var, 4D-Var, and ensemble Kalman filters are common.

Ensemble prediction perturbs initial conditions and model physics to produce a probability distribution of outcomes.

Model spin-up degrades the first hours of a forecast; precipitation forecasts are especially affected.

Post-processing corrects systematic model bias using statistical methods such as model output statistics.

Forecast skill generally decays with lead time; deterministic guidance beyond about 10 days is limited by chaotic error growth.

Climate classification uses temperature and precipitation criteria; Köppen types include A (tropical), B (dry), C (temperate), D (continental), and E (polar).

Brazilian climate regimes: equatorial Amazon, tropical savanna (Cerrado), semi-arid Northeast, and subtropical South with frequent frontal passages.

El Niño-Southern Oscillation alters rainfall: El Niño tends to bring drought to Northeast Brazil and excess rain to the South.

Urban heat islands raise city temperatures by 1-5 K relative to surrounding rural areas.

Climatological normals are 30-year averages used as reference for anomalies and aviation planning.

Agrometeorology uses growing degree days, water balance, and evapotranspiration to support crop management.

Air quality depends on dispersion, which is governed by wind speed, mixing height, and atmospheric stability.

Climate change projections use coupled ocean-atmosphere models and scenario pathways of greenhouse gas concentrations.

ICAO Annex 3 defines METAR, SPECI, TAF, SIGMET, AIRMET, GAMET, and special air-reports; States must provide meteorological service to international air navigation.

METAR is issued hourly; SPECI is issued when significant changes occur; TAF validity is commonly 9, 24, or 30 hours with issue times fixed by the State.

SIGMET informs of severe turbulence, icing, volcanic ash, tropical cyclones, and sandstorms; AIRMET covers less severe phenomena affecting low-level flights.

Wind is reported in degrees true and speed in knots; visibility in meters; cloud base in feet above aerodrome elevation; temperature and dew point in whole degrees Celsius.

QNH is the altimeter setting giving aerodrome elevation on the ground; QFE gives height above the aerodrome; QNE is standard 1013.25 hPa.

Trend forecasts in METAR use BECMG, TEMPO, and NOSIG; change groups have defined time periods.

Brazilian regulation follows ICAO and DECEA norms; REDEMET distributes aeronautical meteorological information nationally.

Volcanic ash and tropical cyclone SIGMETs require advisory coordination with VAAC and TCWC.

Interpretação de texto exige identificar ideia central, argumento, tese e conclusão; a inferência deve apoiar-se em elementos explícitos do texto.

Coesão textual usa referenciação anafórica e catafórica, conectivos e substituição lexical para manter a progressão temática.

Coerência envolve relações lógico-semânticas: causa, consequência, oposição, concessão e finalidade.

Crase ocorre antes de substantivo feminino determinado: 'às 12h', 'à direita'; não ocorre antes de verbo ou palavra masculina.

Concordância verbal: sujeito coletivo, expressões partitivas e sujeito composto posposto ao verbo têm regras específicas.

Regência de verbos como 'assistir', 'visar' e 'implicar' deve ser verificada quanto à preposição exigida.

Ambiguidade e duplo sentido devem ser evitados em textos técnicos e normativos; a clareza prevalece sobre a elegância.

A redação oficial brasileira segue princípios de impessoalidade, clareza, concisão e formalidade.

Standard METAR vocabulary: SKC, FEW, SCT, BKN, OVC for cloud amount; CB and TCU for cumulonimbus and towering cumulus.

Weather codes: RA rain, SN snow, SH showers, TS thunderstorm, GR hail, FZ freezing, BR mist, FG fog, HZ haze.

Wind shear and microburst reports use phrases such as 'windshear on final approach' and 'microburst alert' in plain radiotelephony language.

TAF change groups: BECMG for gradual change, TEMPO for temporary fluctuations, FM for rapid change at a stated time.

ICAO English proficiency requires clear pronunciation, structure, vocabulary, fluency, comprehension, and interactions at operational level 4.

Aviation phraseology avoids nonstandard abbreviations; numbers are spoken digit by digit and 'decimal' replaces the point.

SIGMET text follows a fixed template: phenomenon, location, movement, intensity, and validity period.

Reading comprehension for aviation requires extracting time, location, intensity, and hazard type from coded reports.