Chapter 16,section 4 Water in the atmosphere

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Chapter 16,section 4Water in the atmosphere

• By Rachel Kalin, Billy Mahoney
• Aminata Henderson, Jen Blackey

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Words to know

• Psychrometer An instrument used to measure
  relative humidity, consisting of a wet-bulb
  thermometer and a dry-bulb thermometer.
• Condensation- The process by which a gas, such as
  water vapor, changes to liquid, such as water.
• Dew Point- The temperature at which condensation
  begins.
• Cumulus- Clouds that form less then 2 kilometers
  above the ground and look like fluffy rounded
  piles of cloth.
• Stratus- Clouds that form in flat layers.
• Cirrus- wispy feathery clouds made mostly of ice
  crystals that form at high levels above about a
  kilometer.
• Humidity- A measure of the amount of water vapor
  in the air.
• Relative Humidity- The percentage of water vapor
  in the air compared to the maximum amount the air
  can hold at the temperature.
• Evaporation-Evaporation the act or process of
  evaporating.
• Evaporating to change from a liquid or solid
  state into vapor.
• 1.to give off moisture
• 2.to disappear

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Can you explain to me how relative humidity is
measured?

• Relative humidity is measured with a
  psychrometer. The psychrometer has two
  thermometers, a wet-bulb thermometer and a
  dry-bulb thermometer. The bulb of the wet-bulb
  thermometer has a cloth covering that is
  moistened with thermometers. Because the wet-bulb
  thermometer is cooled by evaporation, its reading
  drops below that of the dry-bulb thermometer. If
  the relative humidity is high, the water on the
  wet bulb will evaporate slowly and the wet-bulb
  temperature will not change much.

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What is the difference between relative humidity
and humidity?

• Humidity is a measure of the amount of water
  vapor in the air and relative humidity is the
  percentage of water vapor in the air compared to
  the maximum amount the air could hold. Humidity
  is the amount and relative humidity is the
  percentage of water vapor in the air.
• Why are the tops of some mountains almost always
  covered by clouds?
• This happens because when wind strikes the side
  of a hill or mountain, the air is forced upward.
  As the air rises along the slope, the air cools.
  Rain or snow falls on the windward side of the
  mountains, the side facing the incoming wind.

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What instrument is used to measure relative
humidity? And how does it work?

• A psychrometer.
• How does it work?
• A psychrometer is an instrument for determining
  atmospheric humidity by the reading of two
  thermometers, the bulb of one being kept moist
  and ventilated.

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How clouds form

• Clouds of all kinds form when water vapor in the
  air becomes liquid water or ice crystals. The
  process by which molecules of water vapor in the
  air become liquid water is called condensation.
  How does water condense? As you know, cold air
  can hold less water vapor than warm air. As air
  cools, the amount of water vapor it can hold
  decreases. Some of the water vapor in the air
  condenses to form droplets of liquid water. The
  temperature at which condensation begins is
  called the dew point. If the dew point is below
  the freezing point, the water vapor may change
  directly into ice crystals. When you look at a
  cloud you are seeing millions of tiny ice
  crystals or water droplets.
• Clouds form whenever air is cooled to its dew
  point and particles are present. But why does the
  air cool? If air is warmed near ground, it
  becomes less dense and rises in a convection
  current.

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Why are the tops of mountains almost always
covered by clouds?

• This happens because when wind strikes the side
  of a hill or mountain, the air is forced upward.
  As the air rises along the slope, the air cools.
  Rain or snow falls on the windward side of the
  mountains, the side facing the incoming wind.

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What conditions are needed for clouds to form?

• Clouds of all kinds form when water vapor in the
  air becomes liquid water ice crystals. Clouds
  form whenever air is cooled to its dew point and
  particles are present.

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Three main types of clouds

• Cirrus- a cloud of a class characterized is thin
  white filaments or narrow bands and a composition
  of ice crystals of high altitude, about
  20,000-40,000 ft.
• Stratus- a cloud of a class characterized by a
  gray, horizontal layer with a uniform base, found
  at a lower altitude than altostratus, usually
  below 8000 feet.
• Cumulus- A cloud of class characterized by dense
  individual elements in the form of puffs, mounds,
  or towers, with flat bases and tops that often
  resemble cauliflower as such clouds develop
  vertically, they form cumulonimbus.

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Low-level, medium-level, high-level clouds

• Altocumulus- high-level
• Altostratus- medium-level
• Cirrostratus- medium-level
• Cirrus- high-level
• Cumulus- low-level
• Fog- low-level
• Nimbostratus- low-level
• Stratus- low-level

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THE END!!