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WEATHER INTERPRETATION
Weather is the state of the atmosphere at any given time or place.
How is weather measured and described?
• Temperature (0C)
• Precipitation (mm for rain) (cm for snow)
• Atmospheric Pressure or Air Pressure (kPa)
• U.V. Sunlight Rating (1 low to 11 extreme)
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Wind (km/hr)
Relative Humidity (%)
Clouds (type)
Atmospheric Pressure
The amount of force pushing on you due to the weight of the air.
High and Low Pressure Systems
When the air is compressed it is under “high pressure”.
Weather forecasters measure air pressure with a Barometer.
Standard Atmospheric Pressure is 101.325 kPa
Atmospheric Pressure and Weather
Air pressure can tell us about what kind of weather to expect as well.
If a high pressure system is on its way, you can expect cooler temperatures and clear skies.
If a low pressure system is coming, then look for warmer weather, storms and rain.
Wind
Wind is air that is moving from a high pressure system to a low pressure system.
The spinning of the Earth also creates wind (The Coriolis Effect). This causes prevailing westerly winds in N. America.
Clouds
Most clouds are associated with weather.
They are divided into groups based on the height of the cloud’s base about the Earth’s surface.
High Clouds (“Cirr”) 5 000 – 13 000m
• made of ice crystals due to the cold air in the upper sky
• not really associated with daily weather
Middle Clouds (“Alto”) 2 000 – 7 000m
Altostratus – covers whole sky, blue-gray appearance.
They usually form ahead of storms with continuous
rain or snow.
Altocumulus – form in groups (grayish-white). They are about
as wide as your thumb when you hold up your hand at a
length. If you see them on a warm humid morning, expect
thunderstorms by afternoon.
Low Clouds (“Strat”) Surface – 2 000m
Status – looks like a fog that doesn’t
reach the ground. Light mist or drizzle
is sometimes associated with these
clouds.
Nimbostratus – dark gray with a
“ragged” base. They are associated
with continuous rain or snow.
Stratocumulus – are low, lumpy and
gray. They can look like cells under a
microscope.
Clouds with Vertical Growth (“Cumu”) Surface – 13 000m
• These clouds grow high up into the atmosphere rather than spreading out.
Cumulus – cloud puffs that are about the size of your
fist when you hold up your hand at arm’s length.
Cumulonimbus – thunderstorm clouds. Dark and
huge.
Canoe Trip Equipment (related to Weather)
 PFD with whistle
 Rain suit
 Tarp and rope (for shelter)
 Weather radio
 Satellite phone
 Canoe should be equipped with a buoyant line and bailer
 Clothes that dry quickly made of nylon, (avoid cotton and wool)
Canoe Trip Safety (related to Weather)
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canoes will come off the water immediately when thunder is heard or lightening is seen
knowledge of windy and choppy water paddling techniques
rain gear is readily accessible at all times
knowledge of buddy system and buddy canoe system
canoe tipping and search and rescue plan in place
http://www.theweathernetwork.com/weather/caon0081
http://www.weatheroffice.gc.ca/radar/index_e.html?id=ONT
http://www.windows2universe.org/earth/Atmosphere/clouds/cloud_types.html