American Meteorological Society Certification Thermodynamics and Atmospheric Stability 1 — Questions and Answers
Question 1: What does the dry adiabatic lapse rate (DALR) represent?
- Rate of temperature decrease in the stratosphere
- Rate at which unsaturated air cools as it rises (≈9.8°C/km) (Correct answer)
- Rate of surface warming at noon
- Temperature gradient across a front
Correct answer: Rate at which unsaturated air cools as it rises (≈9.8°C/km)
The DALR (~9.8°C/km) is the rate at which a dry (unsaturated) air parcel cools as it rises adiabatically.
Question 2: What is the Lifted Index (LI) used to assess?
- Upper-level wind speed
- Atmospheric stability and convective potential (Correct answer)
- Soil moisture availability
- Fog formation likelihood
Correct answer: Atmospheric stability and convective potential
The Lifted Index measures stability by comparing the temperature of a lifted parcel to the environment at 500 hPa; negative values indicate instability.
Question 3: What is the Level of Free Convection (LFC)?
- The height where winds become geostrophic
- The level where a lifted parcel becomes warmer than the environment and rises freely (Correct answer)
- The base of the stratocumulus layer
- The level where wind shear maximizes
Correct answer: The level where a lifted parcel becomes warmer than the environment and rises freely
The LFC is the altitude where a lifted parcel's temperature first exceeds the environmental temperature, allowing free convective ascent.
Question 4: CAPE (Convective Available Potential Energy) is measured in which units?
- Meters per second
- Joules per kilogram (J/kg) (Correct answer)
- Pascals
- Kelvin
Correct answer: Joules per kilogram (J/kg)
CAPE is expressed in J/kg and represents the positive buoyant energy available to a rising parcel of air.
Question 5: A temperature inversion in the lower atmosphere refers to what condition?
- Temperature decreasing with height at an abnormally fast rate
- Temperature increasing with height rather than decreasing (Correct answer)
- Temperature remaining constant with height
- Rapid temperature fluctuations at the surface
Correct answer: Temperature increasing with height rather than decreasing
An inversion occurs when temperature increases with altitude, creating a stable layer that suppresses vertical mixing.
Question 6: Equivalent potential temperature (theta-e) is conserved in which atmospheric process?
- Dry adiabatic ascent only
- Both dry and moist (saturated) adiabatic processes (Correct answer)
- Diabatic heating
- Radiative cooling
Correct answer: Both dry and moist (saturated) adiabatic processes
Theta-e is conserved during both dry and moist adiabatic processes, making it useful for tracing air masses through phase changes.
American Meteorological Society Certification Thermodynamics and Atmospheric Stability 1
What does the dry adiabatic lapse rate (DALR) represent?