Answer to Question 1
ANSWER: Mountain ranges disrupt the idealized pattern of global precipitation (1) by promoting convection (because their slopes are warmer than the surrounding air) and (2) by forcing air to rise along their windward slopes (orographic uplift). Consequently, the windward side of mountains tends to be wet. As air descends and warms along the leeward side, there is less likelihood of clouds and precipitation. Thus, the leeward (downwind) side of mountains tends to be dry. A region on the leeward side of a mountain where precipitation is noticeably less is called a rain shadow.
Answer to Question 2
ANSWER: In the cold air of the polar regions there is little moisture, so there is little precipitation. Winter storms drop light, powdery snow that remains on the ground for a long time because of the low evaporation rates. In summer, a ridge of high pressure tends to block storm systems that would otherwise travel into the area; hence, precipitation in polar regions is meager in all seasons.
Sun Rain
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Typical secondary ignition pattern. Note the lack of firing lines on superimposed pattern.
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