A3-9. The difference between gradient wind and geostrophic wind is that gradient wind
flow is parallel to the curved portion of the analysis. Geostrophic wind is the
windflow that is parallel to that portion of the analysis showing straight flow.
A3-10. The relationship between centrifugal force and pressure gradient force around
anticyclones is that the centrifugal force acts with the pressure gradient force.
A3-11. Anticyclogenesis is the term defined as the formation of an anticyclone or the
intensification of an existing one.
A3-12. The direction of windflow around a cyclone is counterclockwise in the northern
A3-13. The temperatures in a cold core low decrease toward the center.
A3-14. Low pressure due to intense heating in the southwestern United States is an
example of a warm core low.
A3-15. Monsoon winds are caused by the unequal heating and cooling of land and water
A3-16. Land and sea breezes are caused by the diurnal (daily) contrast in the heating of
local water and land areas.
A3-17. Bernoulli's theorem states that pressures are least where velocities are greatest,
and pressures are greatest where velocities are least.
A3-18. A valley breeze usually reaches it's maximum strength in the early afternoon.
A3-19. An eddy is caused when the wind flows over or adjacent to rough terrain,
buildings, mountains or other obstructions.
A3-20. Foehn winds are caused by adiabatic heating of descending air on the lee sides of
A4-1. An air mass is a body of air extending over a large area (usually 1,000 miles or
A4-2. The two primary factors necessary to produce an air mass are a surface whose
properties are relatively uniform and a large divergent flow.
A4-3. Maritime tropical air that is colder than the surface over which it is moving is
written as mTk.
A4-4. The modifying factors on air mass stability are thermodynamic and mechanical.
A4-5. Superior air is the warmest air mass observed in the United States at its altitude.
A4-6. A frontal surface is the surface that separates the air masses.
A4-7. The frontal zone is located between the air masses of different densities.
A4-8. The difference between a stable wave and an unstable wave is that a stable wave
neither develops nor occludes. An unstable wave develops along the polar front
and usually occludes.
A4-9. Frontogenesis occurs where there is a concentration of isotherms with the
circulation to sustain that concentration.
A4-10. The polar front in winter is usually found off east coasts of continents between 30
and 60 degrees latitude.