KMA Grade 9 Meteorologist flashcards

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

Hydrostatic equation

Expresses vertical pressure gradient balancing gravity: dp/dz = -ρg. It holds well for large-scale flow and underlies the hypsometric thickness relation and altimetry.

Geostrophic wind

The horizontal wind for which Coriolis force exactly balances the pressure-gradient force. It blows parallel to straight isobars with low pressure to the left in the Northern Hemisphere.

Coriolis parameter

f = 2Ω sin φ, where Ω is Earth's rotation rate and φ is latitude. It is zero at the equator and near 1.46×10⁻⁴ s⁻¹ at 30° latitude.

Rossby radius of deformation

The horizontal scale at which rotational and buoyancy effects balance, LR = NH/f. Disturbances much larger than LR are balanced; smaller ones radiate gravity waves.

Ertel potential vorticity

PV = (1/ρ)·ζa·∇θ, the dot product of absolute vorticity and potential temperature gradient divided by density. It is conserved in adiabatic, frictionless flow.

Thermal wind relation

The vertical shear of the geostrophic wind is proportional to the horizontal temperature gradient. Wind veers with height during warm advection and backs during cold advection.

Quasi-geostrophic omega equation

Diagnoses vertical motion from differential vorticity advection and temperature advection. Ascent occurs with positive vorticity advection increasing with height and with warm-air advection.

Potential temperature

θ = T·(p0/p)^(Rd/cp), with p0 = 1000 hPa. It is the temperature an air parcel would have if brought adiabatically to the reference pressure, and is conserved in dry processes.

Equivalent potential temperature

θe combines potential temperature with latent heat released on condensation. It is conserved during moist adiabatic ascent and labels air masses by their heat and moisture content.

Dry adiabatic lapse rate

Γd = g/cp ≈ 9.8 K per km. It is the rate at which an unsaturated parcel cools when lifted adiabatically, and it is a constant in a dry atmosphere.

Clausius-Clapeyron relation

Saturation vapor pressure increases roughly 6-7% per kelvin of warming. This exponential dependence governs moisture availability and heavy-rainfall potential in a warming climate.

Lifting condensation level

The height where an ascending parcel first reaches saturation. It can be estimated as about 125 m per degree of surface dew-point depression.

Convective available potential energy

CAPE is the buoyant energy integral between the level of free convection and the equilibrium level. Larger CAPE supports stronger updrafts, but shear and inhibition also matter.

Wet-bulb temperature

The temperature an air parcel reaches when water evaporates into it adiabatically to saturation. It lies between the dry-bulb and dew-point temperatures and governs evaporative cooling.

Skew-T log-p diagram

A thermodynamic chart with skewed isotherms and logarithmic pressure. Dry adiabats, moist adiabats, and mixing-ratio lines allow parcel-path analysis of stability and cloud layers.

Norwegian frontal cyclone model

Describes a low forming on the polar front, with warm and cold fronts and an occlusion as the cold front overtakes the warm front. It remains the basis for surface analysis symbols.

Mesocyclone

A rotating updraft within a supercell thunderstorm, typically 2-10 km in diameter. It appears as a couplet of inbound and outbound Doppler velocities and may produce tornadoes.

Squall line

A line of intense convective cells, often along or ahead of a cold front. Hazards include damaging straight-line winds, hail, and brief tornadoes at line ends.

Sea-breeze front

The leading edge of cool marine air advancing inland due to differential heating. It can trigger convection and typically penetrates 10-50 km inland.

Tropical cyclone warm core

A positive temperature anomaly in the upper troposphere produced by latent heat release in the eyewall. It distinguishes tropical cyclones from cold-core mid-latitude lows.

Frontogenesis

The process that increases horizontal temperature gradient, driven by confluence, shear, and diabatic heating. It sharpens fronts and strengthens the associated secondary circulation.

Jet streak quadrants

Regions around a wind maximum aloft where ageostrophic flow favors divergence. The left-exit and right-entrance quadrants are preferred zones for ascent and cyclogenesis.

Station model plot

A compact surface-observation symbol showing temperature, dew point, pressure, pressure tendency, cloud cover, wind direction and speed, and present weather around a station circle.

Brier score

A verification metric for probabilistic forecasts: the mean squared difference between forecast probability and observed outcome. Lower values indicate better calibrated forecasts.

Persistence forecast

A baseline forecast assuming current conditions continue unchanged. It is a standard benchmark used to judge whether a numerical model adds skill.

Nowcasting

Short-range forecasting, typically 0-6 hours, based on radar extrapolation, satellite trends, and surface observations. Skill decays rapidly as convection evolves.

Planetary albedo

The fraction of incoming solar radiation reflected back to space, about 0.30 for Earth. It is dominated by clouds, ice, and bright desert surfaces.

Effective emission temperature

The temperature at which Earth would radiate absorbed solar energy as a blackbody, about 255 K. The observed surface is warmer because of the greenhouse effect.

Equilibrium climate sensitivity

The equilibrium global-mean surface warming for a doubling of atmospheric CO2, likely between about 2.5 and 4 °C. Transient response is lower because of ocean heat uptake.

El Niño-Southern Oscillation

A coupled ocean-atmosphere cycle in the tropical Pacific. El Niño features warm eastern Pacific sea surface temperatures and a weakened Walker circulation; La Niña is the opposite phase.

Köppen climate classification

A scheme dividing climates by monthly temperature and precipitation thresholds into tropical, dry, temperate, continental, and polar groups, with subcategories based on seasonality.

Doppler radar velocity folding

Ambiguity in radial velocity when true wind speed exceeds the Nyquist velocity. Returns appear with reversed sign, requiring dealiasing before interpretation.

Data assimilation

The process of combining observations with a short-range model background to produce the analysis. Techniques include 4D-Var and the ensemble Kalman filter.

Ensemble prediction

Running many model forecasts with perturbed initial conditions and physics to sample uncertainty. The member spread indicates forecast confidence and yields probabilities.

Model parameterization

Approximate formulas representing subgrid processes such as convection, radiation, turbulence, and microphysics. Their errors are a major source of forecast uncertainty.

Water vapor satellite channel

An infrared channel near 6.7 µm sensitive to mid-tropospheric moisture. Bright (white) areas indicate moist air and cloudy features; dark areas indicate dry, subsiding air.

Model Output Statistics

A statistical post-processing method relating model forecast variables to observed station conditions. It corrects systematic biases and improves local temperature and precipitation forecasts.