Chapter 11 - Air masses and fronts Flashcards
Explain how the air aloft regulates the movement of air masses.
The air mass itself is generally uniform with low winds, so its movement is almost entirely dictated by the air movements aloft that push on the air mass, moving it around
The boundaries between neighbouring air masses tend to be more distinct during winter than during the summer. Explain why.
During the summer, cold fronts become warmer due to more direct sunlight thus not having such a huge difference in temperature and humidity when meeting another air mass.
Where is the precipitation around a a) Cold front b) Warm front c) Occluded front
a) Small corridor around the front b) a large area in front of the front c) Small corridor around the front.
What type of clouds occur around a a) cold front b) warm front c) occluded front
a) Cirrus and cirrostratus in front and Cumulonimbus behind the front and altocumulus over the front b) Cirrus and cirrustratus in front, altocumulus and altostratus behind these, nimbusstratus before these and stratus and fog right in front of the front. Stratucumulus behind the front. c) Similar to warm front.
Suppose a maritime polar air mass moving eastward from the Pacific Ocean travels across the US. Describe all of the modifications that could take place as this air mass moves eastward in winter. In summer
In winter, as the mP reaches the Pacific Coast it is cool, moist, and conditionally unstable. The surface air will be warmer than the air aloft. Common temps would be around 40 degrees to 50 near the surface while the air a kilometer aloft could be freezing. As it moves inland, coastal mountains force it to rise andmuch of it water vapor condenses into rain-producing clouds In colder air the aloft, the rain changes to snow, with heavy amounts accumulating in mountain regions. It loses much of its moisture as it crosses aseries of mountain regions. Beyond these mountains, it travels over a cold, elevated plateau that chills the surface air and slowly transforms the lower level into dry stable cP air. See image on p. 301.
Explain how an anticyclone during autumn and summer can bring record-breaking low temperatures and continental polar air to the southeastern states, and only a day or so later very high temperatures and maritime tropical air to the same region.
As an anticyclone moves into a region that region is usually on the eastern side of the anticyclone where winds are northerly and cold and often deliver cP air. Later, because of the common easterly shift of long wave patterns in the upper-air flow along the western boundary of the anticyclone which may carry mT air into the region. If the anticyclone’s eastern edge and the warm, southerly flow on the anticyclones western edge are especially strong and record-breaking temps can be set at both extremes by the same system.
Explain why freezing rain more commonly occurs with warm fronts than with cold fronts.
Freezing rain is more common with warm fronts because with a warm front, warm air rides up and over cold surface air. It is the warm rain falling into the cold, stable surface air that produces freezing rain. Often, behind a cold front the air becomes colder aloft.
In winter, cold front weather is typically more violent than warm-front weather. Why? Explain why this is not necessarily true in summer.
The temperature gradient is much grater for the cold front and is over a smaller area which makes the weather more intense. In summer the difference between temperature is much smaller.
What are lake-effect and how do they form? On which side of the lake do they typically occur?
On the down-wind side of a lake. Cold air flows over hot water and evaporates, making the air unstable. Creates big cumulus clouds. Terrain/mountains make it go higher which makes the cloud colder. Produces lots of snow and very local.
