Ch. 8 Questions for Review

11.) What type of air mass would be responsible for the weather conditions listed below? (a) hot, muggy summer weather in the Midwest and the East; (b) refreshing, cool, dry breezes after a long summer hot spell on the Central Plains; (c) persistent cold, damp weather with drizzle along the East Coast; (d) drought with high temperatures over the Great Plains; (e) record-breaking low temperatures over a large portion of North America; (f) cool weather with showers over the Pacific Northwest; (g) daily afternoon thunderstorms along the Gulf Coast.

( a) maritime topical air mass over the Caribbean. (b) continental polar air mass over central Canada. (c) maritime polar air mass over the north Atlantic. (d) continental tropical air mass over northern Mexico and the southwest United States. (e) continental polar air mass moving down from the Arctic and central Canada. (f) maritime polar air mass over the northern Pacific. (g) maritime tropical air mass over the Gulf of Mexico.

17.) Why is it important that for a surface low to develop or intensify, it's upper-level counterpart must be to the left (or west) of the surface storm?

A surface low can begin to develop into a major storm system when more air is removed from above the developing storm that is brought into the storm at the surface. In other words, the upper-level divergence of air must be greater than the surface convergence of air. This can only occur if the upper-level trough is to the west (left) of the surface low.

5.) Explain why the central United States is not a good air-mass source region.

Air masses form over large areas where conditions of temperature, pressure, and humidity remain stable for weeks, even months. The central United States is not a good air-mass source region because it is located in the middle latitudes where westerly winds constantly stir the air. Such mixing of air causes constant fluctuation of temperature and pressure.

TE-2.) Explain how an autumn anticyclone can bring record low temperatures and continental polar air to the southeastern United States and, only a day or so later, bring record high temperatures and maritime tropical air to the same region.

An anticyclone is a region of high atmospheric pressure at its center in which air slowly circulates in a clockwise direction in the northern hemisphere. On the eastern side of an anticyclone, the winds are northerly and cold and often deliver continental polar air. As the system shifts towards the east, the western side of the anticyclone moves over the same region delivering southerly, warm air into the area.

4.) What are lake-effect snows and how do they form? On which side of a lake do they typically occur?

Lake-effect snow is a heavy, localized snowfall associated with the Great Lakes in particular. In the winter, lake-effect snows form when cold air moves over warmer lake water. Lake moisture evaporates up into the cold air as the bottom layer of cold air is heated by the warmer lake water. This now-warmed air begins to rise and cool and the moisture within it begins to condense forming clouds and then snow. Lake-effect snow typically forms on the downward side of a lake. Lake Erie and Lake Ontario are positioned in such a way that prevailing winds from the west blow the entire length of the lakes often generating huge amounts of snow that fall on the east end (downwind side) of the lakes and surrounding land.

TE-5.) Why does the same cold front typically produce more rain over Kentucky than over western Kansas?

Precipitation associated with a cold front is produced when an advancing wedge of cold, dense air displaces warmer moist air on front of it. As the warmer air rises, the moisture within it cools, condenses, and falls as precipitation. Because the absolute humidity (amount of moisture in the air) is generally higher in Kentucky than in Kansas, there is more moisture available to fall as precipitation in Kentucky than in Kansas.

14.) Describe the stages of a developing mid-latitude cyclonic storm using the polar front theory.

The polar front is a global boundary that separates the colder air from the warmer subtropical air. Mid-latitude cyclones form and move along the polar front in a sequence of stages: Stage 1: A wave-like kink known as a frontal wave forms on the stationary front between the cold air and warm air masses. Stage 2: The wave front begins to rotate with cold air moving south as a cold front and warm air moving north as a warm front. Steered by winds aloft, the system moves east or northeast gradually becoming a fully developed open wave. Stage 3: As the open wave (cyclone) moves eastward, the cold front overtakes the warm front resulting in an occlusion. Stage 4: The mature cyclone is cut-off from the warm air and begins to dissipate.