NAV Brasil Aeronautical Meteorologist flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Dry adiabatic lapse rate

The rate at which a parcel of dry air cools when lifted adiabatically, approximately 9.8 K per kilometer, derived from the ratio of gravity to specific heat at constant pressure.

Potential temperature

The temperature a parcel would have if brought adiabatically to a reference pressure of 1000 hPa; it is conserved in dry adiabatic processes and identifies air masses.

Equivalent potential temperature

A conserved quantity in moist adiabatic processes that accounts for latent heat release; it is used to compare air masses and assess conditional instability in the atmosphere.

Lifting condensation level

The height at which a rising parcel reaches saturation; estimated as about 125 meters per degree Celsius of dew-point depression, marking the cloud base.

Geostrophic wind

The horizontal wind resulting from exact balance between the pressure gradient force and the Coriolis force, blowing parallel to height contours in the free atmosphere.

Thermal wind relation

A relationship stating that vertical shear of the geostrophic wind is proportional to the horizontal temperature gradient, with cold air to the left in the Southern Hemisphere.

Quasi-geostrophic omega equation

A diagnostic equation showing that ascent is forced by positive vorticity advection increasing with height and by warm temperature advection, while the opposite forces descent.

Rossby wave speed

The phase speed of a barotropic Rossby wave, given by the mean zonal wind minus a term proportional to beta divided by the square of the zonal wavenumber.

Squall line

A line of active thunderstorms that propagates as a coherent system, often producing strong gust fronts, heavy rain, hail, and hazardous low-level wind shear.

Sea breeze circulation

A thermally direct circulation driven by land-sea temperature contrast, with onshore flow near the surface reaching tens of kilometers inland and a return flow aloft.

Tropical cyclone formation requirements

Sea-surface temperature above about 26.5 degrees Celsius, weak vertical wind shear, sufficient Coriolis parameter away from the equator, and a pre-existing disturbance.

Cut-off low

A closed upper-level low detached from the main westerly flow, which moves slowly and produces persistent cloud, rain, and forecast uncertainty over affected regions.

Skew-T log-p diagram

A thermodynamic chart with skewed temperature lines and logarithmic pressure, used to plot soundings and derive CAPE, convective inhibition, and parcel paths.

Convective available potential energy

The vertically integrated buoyant energy available to a rising parcel between its level of free convection and equilibrium level, expressed in joules per kilogram.

Threat score

A verification measure equal to hits divided by the sum of hits, misses, and false alarms; it ranges from zero to one and rewards correct event forecasts.

Microburst

A localized strong downdraft producing an outburst of damaging wind at the surface, typically less than four kilometers in diameter and hazardous to aircraft.

Clear air turbulence

Turbulence occurring in cloud-free air, often near jet streams, mountain waves, or tropopause folds, and invisible to airborne weather radar.

Volcanic ash SIGMET

A warning message issued for volcanic ash that may affect flight safety, specifying the ash cloud location, movement, and validity period for aviation users.

Aircraft icing conditions

Supercooled water droplets in clouds between zero and about minus twenty degrees Celsius that freeze on impact with airframe surfaces, adding weight and reducing lift.

Radiosonde observation

An instrument package carried aloft by balloon that measures temperature, humidity, and pressure and derives wind, typically launched at 0000 and 1200 UTC.

Radar reflectivity factor

A measure of returned radar power proportional to the sixth power of drop diameter per unit volume, related to rainfall rate by empirical Z-R relationships.

Ceilometer

A lidar or laser-based instrument that measures cloud base height by timing backscatter from cloud particles, reporting ceiling for aviation operations.

Geostationary satellite

A satellite at about 35,786 kilometers altitude whose orbital period matches Earth's rotation, providing continuous views of the same hemisphere.

Water vapor channel

A satellite infrared channel near 6.2 micrometers that senses upper-tropospheric moisture, revealing jet stream structure and dry intrusions.

Doppler radar velocity product

A display of radial velocity toward or away from the radar, used to detect rotation in storms, convergence lines, and gust fronts.

Data assimilation

The process of combining observations with a short-range model background, weighted by their respective error covariances, to produce the initial state for a forecast.

Ensemble prediction

A forecasting technique that runs multiple model integrations with perturbed initial conditions or physics to estimate the probability distribution of possible outcomes.

Model parameterization

The representation of sub-grid processes such as convection, turbulence, radiation, and cloud microphysics by simplified physical schemes within a numerical weather prediction model.

El Nino Southern Oscillation

A coupled ocean-atmosphere oscillation altering global rainfall patterns; El Nino tends to bring drought to Northeast Brazil and excess rainfall to the South.

QNH altimeter setting

The pressure setting that, when entered on an altimeter, causes it to indicate aerodrome elevation when the aircraft is on the ground at that aerodrome.

SPECI report

A special aerodrome weather report issued when specified significant changes in wind, visibility, cloud, or weather occur between routine hourly METAR observations.

Crase

A fusao de duas vogais identicas, representada pelo acento grave, que ocorre antes de substantivo feminino determinado, como em 'as doze horas' escrito com acento.