Transcript Atmospheric Conditions and the Water Cycle

Atmospheric Conditions and the
Water Cycle
Atmospheric Conditions
The atmosphere of Earth is a layer of gases
surrounding the planet Earth
Atmospheric Conditions
• atmospheric condition - the atmospheric
conditions that comprise the state of the
atmosphere in terms of temperature and wind
and clouds and precipitation
• Weather is the state of the atmosphere at a
given time and place.
How Clouds Form
• Water vapor
• Cool air
• Dust particles
How Clouds Form
• Water vapor
When water is heated by the sun it evaporates
and becomes water vapor
How Clouds Form
• Cool air
When temperatures or pressures decrease,
the air cannot hold as much water. When air is
cold the water vapor begins to condense and
form clouds.
How Clouds Form
• Dust particles
(Cloud Condensation Nuclei)
Clean air (without any dust or particles) will
not produce clouds. This dust comes from
sources such as volcanoes, cars, sea spray
from the ocean, and fires.
Humidity
• Humidity is the amount of water vapor in the
air.
• Warm air can hold more water vapor than
cold air
• High humidity makes people feel hotter
outside in the summer because it reduces the
effectiveness of sweating to cool the body by
reducing the evaporation of perspiration from
the skin.
Evaporation
Factors that effect the rate of evaporation
• Temperature: Warm temperatures cause
water it evaporate more quickly
• Wind: Water will evaporate more quickly on a
windy day
Dew and Frost Formation
• Dew point is the temperature at which water
vapor becomes liquid or solid usually forming
rain, snow, frost, or dew.
• Dew point normally occurs when a mass of air
has a relative humidity of 100%.
(This means the air is saturated or it has
absorbed all of the water it can hold)
Dew and Frost Formation
• Dew is water in the form of droplets that
appears on thin, exposed objects in the
morning or evening.
• If the dew point is above freezing dew will
form.
• Frost is the solid or frozen deposition of water
vapor from saturated air.
• If the dew point is below freezing, it is
referred to as the frost point.
Precipitation
• Rain: Non frozen precipitation
• Snow: Snowflakes form when tiny supercooled cloud
droplets freeze (stay frozen).
• Sleet: Ice pellets that form when snowflakes melt and then
re-freeze into ice pellets. (freeze then melt and re-freeze)
• Hail forms in storm clouds when supercooled water
droplets freeze on contact. The storm's updraft blows the
hailstones to the upper part of the cloud ( making the ice
pellet bigger each time).(freeze because of storm)
• Freezing Rain: When snowflakes melt but do not have time
to re-freeze. ( freeze then melt)