American Meteorological Society Certification Thermodynamics and Atmospheric Stability 2 — Questions and Answers
Question 1: What does the CIN (Convective Inhibition) represent on a sounding?
- Energy available for downdrafts
- Energy that must be overcome by lifting to reach the LFC (Correct answer)
- Maximum updraft speed
- Boundary layer moisture content
Correct answer: Energy that must be overcome by lifting to reach the LFC
CIN represents the negative buoyancy energy that must be overcome before a parcel can reach the LFC and convect freely.
Question 2: The moist adiabatic lapse rate (MALR) is approximately what value near the surface?
- 9.8°C/km
- 4–7°C/km (Correct answer)
- 12°C/km
- 1°C/km
Correct answer: 4–7°C/km
The MALR varies from about 4°C/km in warm moist air to 7°C/km in cooler air, less than the DALR due to latent heat release.
Question 3: What is potential temperature (theta) and why is it useful?
- Temperature at a fixed altitude; useful for comparing elevations
- Temperature a parcel would have if brought adiabatically to 1000 hPa; conserved in dry adiabatic motion (Correct answer)
- Temperature corrected for moisture; used in tropical analysis
- Effective temperature felt by observers at the surface
Correct answer: Temperature a parcel would have if brought adiabatically to 1000 hPa; conserved in dry adiabatic motion
Potential temperature is conserved during dry adiabatic processes, making it ideal for identifying airmass properties and stability.
Question 4: What type of lapse rate produces absolutely unstable conditions?
- Lapse rate less than the MALR
- Lapse rate greater than the DALR (Correct answer)
- Lapse rate equal to the MALR
- Isothermal layer
Correct answer: Lapse rate greater than the DALR
Absolute instability occurs when the environmental lapse rate exceeds the dry adiabatic lapse rate (~9.8°C/km), causing any parcel to accelerate upward.
Question 5: On a Skew-T log-P diagram, the dew point profile indicates what?
- Wind speed at each level
- Moisture content as a function of pressure (Correct answer)
- Temperature inversions only
- Cloud top height
Correct answer: Moisture content as a function of pressure
The dew point profile on a Skew-T shows the moisture content of the atmosphere as a function of pressure level.
Question 6: What stability index combines wind shear and instability to assess severe weather potential?
- K-Index
- Storm Relative Helicity (SRH) (Correct answer)
- Showalter Index
- Totals-Totals Index
Correct answer: Storm Relative Helicity (SRH)
Storm Relative Helicity (SRH) measures the potential for rotating updrafts by combining low-level wind shear with the storm motion vector.
American Meteorological Society Certification Thermodynamics and Atmospheric Stability 2
What does the CIN (Convective Inhibition) represent on a sounding?