Mixed Deck — All AMS Topics Flashcards

The Milankovitch cycles describe climate variability caused by:

Answer: Periodic variations in Earth's orbital parameters

Milankovitch cycles refer to variations in Earth's eccentricity, axial tilt, and precession that alter the distribution and intensity of solar radiation reaching Earth.

What does Doppler radar velocity data measure that standard reflectivity cannot?

Answer: Radial wind velocity (toward or away from the radar)

Doppler radar measures the phase shift of returned radar pulses to determine the radial velocity of precipitation moving toward or away from the radar.

Which equation describes the conservation of mass in atmospheric dynamics?

Answer: Continuity equation

The continuity equation ensures that mass is neither created nor destroyed within an air volume.

Ground-based microwave radiometers in meteorology are used primarily for what purpose?

Answer: Profiling temperature and humidity through the lower troposphere continuously

Microwave radiometers passively detect thermal emissions from atmospheric oxygen and water vapor to retrieve continuous temperature and humidity profiles.

In a barotropic atmosphere, how do pressure surfaces relate to density surfaces?

Answer: They are parallel (no solenoids)

A barotropic atmosphere has parallel pressure and density surfaces, meaning no baroclinic instability can develop.

The Köppen climate classification system primarily categorizes climates based on:

Answer: Temperature and precipitation patterns

Köppen's system uses monthly and annual temperature and precipitation thresholds, along with seasonal patterns, to define five major climate zones and their subtypes.

What is the El Niño-Southern Oscillation (ENSO) and how does it affect US winter weather?

Answer: A coupled ocean-atmosphere oscillation that modulates global climate; El Niño typically brings wetter conditions to southern US and drier/warmer to the north

ENSO alternates between El Niño (warm Pacific SSTs) and La Niña (cool SSTs), creating significant teleconnections that shift storm tracks and temperature patterns across the US.

El Niño conditions in the tropical Pacific are characterized by:

Answer: Warmer-than-normal SSTs in the central and eastern tropical Pacific

El Niño is defined by anomalously warm sea surface temperatures in the central and eastern equatorial Pacific, which weaken the Walker circulation and alter global weather patterns.

In hydrological forecasting, what is the Flash Flood Guidance (FFG) product?

Answer: The amount of rainfall needed over a specific duration to initiate flash flooding in a given area

FFG represents the rainfall amount required over a specified duration (1, 3, 6 hours) to cause small stream flooding in a given hydrologic area.

What is the purpose of the Storm Prediction Center (SPC) in the US?

Answer: Issuing outlooks, watches, and mesoscale discussions for severe thunderstorms, tornadoes, and winter storms

The SPC (Norman, OK) issues convective outlooks from day 1–8, tornado and severe thunderstorm watches, and mesoscale discussions for the contiguous US.

What does the Velocity Azimuth Display (VAD) technique provide from Doppler radar data?

Answer: Vertical wind profiles at the radar site

The VAD technique uses a full 360° radar scan at constant elevation to derive mean wind speed and direction as a function of altitude.

What is Q-vector divergence used to diagnose in synoptic meteorology?

Answer: Vertical motion without computing vorticity separately

Q-vector divergence provides a direct measure of synoptic-scale vertical motion without separating vorticity and thermal advection terms.

Which surface feature is commonly found along the boundary between dry continental and moist Gulf of Mexico air in the US?

Answer: Dryline

The dryline is a moisture boundary common over the US Great Plains, separating moist Gulf air from dry continental air.

The standard climatological reference period used by the World Meteorological Organization (WMO) to define climate normals is:

Answer: 30 years

WMO defines climate normals as 30-year averages (currently 1991–2020) to provide a stable statistical baseline that smooths interannual variability.

Atmospheric CO2 concentrations have surpassed approximately what level in recent years (mid-2020s)?

Answer: 420 ppm

Atmospheric CO2 concentration has exceeded 420 ppm in the 2020s, compared to the pre-industrial level of approximately 280 ppm, representing a ~50% increase driven by fossil fuel combustion and land-use change.

The Planck feedback in the climate system is classified as:

Answer: A fundamental negative feedback that stabilizes climate

The Planck (blackbody) feedback is a stabilizing negative feedback: as surface temperature increases, the planet emits more longwave radiation to space, acting as a restoring force against further warming.

What does divergence in the upper atmosphere typically indicate at the surface?

Answer: Surface low pressure and rising motion

Upper-level divergence removes mass from a column, lowering surface pressure and promoting rising motion.

The Model Output Statistics (MOS) technique improves NWP forecasts by doing what?

Answer: Applying statistical relationships between model output and observed weather to reduce systematic errors

MOS uses regression relationships derived from historical model errors and observations to generate bias-corrected, site-specific forecast guidance.

What does ensemble forecasting provide compared to a single deterministic model run?

Answer: Probabilistic forecast information by running multiple model simulations with varied initial conditions

Ensemble forecasting produces a range of possible outcomes by perturbing initial conditions and model physics, quantifying forecast uncertainty.

What is the purpose of ASOS (Automated Surface Observing System) stations in the US?

Answer: Automated surface weather observations for aviation and public use

ASOS stations provide automated, continuous surface weather observations including temperature, dew point, wind, visibility, and present weather.