Answer to Question 1
ANSWER: Longwaves are also known as planetary waves and as Rossby waves, after C.G. Rossby, a famous meteorologist who carefully studied their motion. Imbedded in longwaves are shortwaves, which are small disturbances, or ripples that move with the wind flow. Rossby found that the shorter the wavelength of a particular wave, the faster it moved downstream. Shortwaves tend to move eastward at a speed proportional to the average wind flow near the 700-mb level, about 3 km above sea level. Longwaves, on the other hand, often remain stationary, move eastward very slowly at less than 4 degrees of longitude per day (about 8 knots), or even move westward (retrograde). We can obtain a better idea of this wave movement if we think of longwaves as being huge meanders (loops) in a swiftly flowing stream of water. Water moves through the loops quickly, while the loops themselves move eastward very slowly, as the fast-flowing water cuts away at one bank and deposits material on the other. Suppose debris tumbles into the stream, disturbing the flow. The disturbed flow appears as a small wrinkle that travels downstream through the loops at a speed near the average stream flow. This wrinkle in the flow is analogous to a shortwave in the atmosphere.
Answer to Question 2
ANSWER: As a parcel of air moves with the upper-level flow, an increase in its absolute vorticity with respect to time is related to upper-level converging air, and a decrease in its absolute vorticity with respect to time is related to upper-level diverging air.
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