Chapter 15 Answers

  1. In the mesosphere, temperatures start cold and get colder with increasing elevation because there are fewer gas molecules in it to absorb heat. Clouds do not occur in this region of the atmosphere and UV protection is required. In the stratosphere, temperatures start at around -40˚C and warm steadily to around -5˚C, there are no clouds in this region, but volcanic ash may be distributed in it and most of the heat here is from the Sun. This zone contains ozone, which is necessary for life on Earth or it would be much colder than it is. The troposphere is where we find clouds and there is a steady decrease in temperatures from ground level upwards until you reach the mesosphere. The heat here comes from the Earth’s surface.
  2. Clouds are separated into four different groups. High level clouds have little water vapor, and form from ice crystals due to the low temperatures where they form and include cirrus, cirrostratus, and cumulus clouds. Mid-level clouds have both water drops and ice crystals, include both altocumulus and altostratus clouds and are good clues that a storm is coming. Low-level clouds consist nearly entirely of water droplets and can vary in the precipitation energy they create depending on the stability of air currents. Stratusstratocumulus and nimbostratus clouds are common low clouds. Nimbostratus clouds are thick and dark that produce precipitation. Clouds grow vertically when strong unstable air currents are rising upward. Common clouds include cumulus humilis,cumulus mediocriscumulus congestus, and cumulonimbus.
  3. Air masses receive their characteristics from their source region. If a colder air mass moves over warmer ground, the bottom layer of air is heated. That air rises, forming clouds, rain, and sometimes thunderstorms. If a warm air mass moves over colder ground, gentle precipitation is formed.
  4. Fronts include warm, cold, and occluded fronts. A warm front pushes warm air over cold air masses, and are marked by at first, high cirrus clouds, these are in turn replaced by cirro, alto, and nimbostratus clouds and moderate precipitation. A cold front bulldozes under a warm front, displacing warmer air upwards. This interaction is marked by the formation of cumulonimbus clouds which can generate heavy precipitation and in some cases, tornadoes. Occluded fronts are fronts that form around a low pressure system. In these fronts, a cold front catches up to a warm front, rotation occurs, and the rotating air masses from front to back are cold, warm, and the cold again.
  5. Tornadoes are more localized events, whereas hurricanes can cover hundreds of miles and can inflict a much broader span of regional damage than a tornado including storm surge and flooding. Tornadoes are ranked by the EF or Enhanced Fujita Scale, whereas hurricanes are ranked by the Saffir Simpson Scale and both scales use wind speed and damage inflicted to give these storm events their assigned ranking.
  6. Where an air mass receives it’s characteristics of temperature and humidity is called the source region; storms arise if the air mass and the region it moves over have different characteristics. For example, when a colder air mass moves over warmer ground, the bottom layer of air is heated. That air rises, forming clouds, rain, and sometimes thunderstorms.
  7. Pressure differences & the Coriolis Effect make persistent bands of winds that have vertical and horizontal air circulation and this movement of air consists of cells of rotating air at different latitudes. The sbsence or presence of weather depends on the type of air rotated in cells (warm, moist, cool, or dry). Where colder drier air sinks, we can expect more arid conditions. Where warmer, moister air rises, we can expect more humid conditions, since these conditions occur at different latitudes for the different atmospheric cells, we can expect different climates at the rising or sinking portions of the cells.


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