WeatherWeather

Weather is the state of the Weather is the state of the atmosphere at any given atmosphere at any given time or place.time or place.

ClimateClimate

Climate is the average weather conditions that Climate is the average weather conditions that occur in a region over a long period of time.occur in a region over a long period of time.

How is weather How is weather measured and measured and

described?described?•Temperature (Temperature (00C)C)

•Precipitation (mm for rain) (cm for snow)Precipitation (mm for rain) (cm for snow)

•Atmospheric Pressure or Air Pressure (kPa)Atmospheric Pressure or Air Pressure (kPa)

•Wind (km/hr)Wind (km/hr)

•Relative Humidity (%)Relative Humidity (%)

•Clouds (type)Clouds (type)

•U.V. Sunlight Rating (1 low to 11 extreme)U.V. Sunlight Rating (1 low to 11 extreme)

Atmospheric PressureAtmospheric Pressure

The amount of force pushing on you due to The amount of force pushing on you due to the weight of the air.the weight of the air.

High and Low Pressure SystemsHigh and Low Pressure Systems

When the air is compressed it is under “high When the air is compressed it is under “high pressure”.pressure”.

Weather forecasters measure air pressure Weather forecasters measure air pressure with a with a BarometerBarometer..

Standard Atmospheric Pressure is 101.325 Standard Atmospheric Pressure is 101.325 kPakPa

Atmospheric Pressure and Atmospheric Pressure and WeatherWeather

Air pressure can tell us about what Air pressure can tell us about what kind of weather to expect as well. kind of weather to expect as well.

If a If a high pressurehigh pressure system system is on its is on its way, you can expect cooler way, you can expect cooler temperatures and clear skies. temperatures and clear skies.

If a If a low pressure systemlow pressure system is coming, is coming, then look for warmer weather, then look for warmer weather, storms and rain. storms and rain.

WindWind

Wind is air that is moving from a high Wind is air that is moving from a high pressure system to a low pressure pressure system to a low pressure system.system.

The spinning of the Earth also creates The spinning of the Earth also creates wind (wind (The Coriolis Effect)The Coriolis Effect). This . This causes the prevailing westerly winds causes the prevailing westerly winds in North America.in North America.

CloudsClouds

Most clouds are associated with Most clouds are associated with weather.weather.

They are divided into groups based on They are divided into groups based on the height of the cloud’s base about the height of the cloud’s base about the Earth’s surface.the Earth’s surface.

High Clouds High Clouds (“Cirr”)(“Cirr”)• 5 000 – 13 000m5 000 – 13 000m

• made of ice crystals due to the cold air in made of ice crystals due to the cold air in the upper sky the upper sky

• not really associated with daily weathernot really associated with daily weather

Middle Clouds Middle Clouds (“Alto”)(“Alto”)• 2 000 – 7 000m 2 000 – 7 000m

• AltostratusAltostratus – covers whole – covers whole sky, blue-gray appearance. sky, blue-gray appearance. They usually form ahead of They usually form ahead of storms with continuous storms with continuous rain or snow.rain or snow.

• AltocumulusAltocumulus – form in – form in groups (grayish-white). groups (grayish-white). They are about as wide as They are about as wide as your thumb when you hold your thumb when you hold up your hand at arm’s up your hand at arm’s length. If you see them on length. If you see them on a warm humid morning, a warm humid morning, expect thunderstorms by expect thunderstorms by afternoon.afternoon.

Low Clouds Low Clouds (“Strat”)(“Strat”)• Surface – 2 000mSurface – 2 000m• StratusStratus – look like a fog that doesn’t reach the ground. – look like a fog that doesn’t reach the ground.

Light mist or drizzle is sometimes associated with Light mist or drizzle is sometimes associated with these clouds.these clouds.

• StratocumulusStratocumulus – are low, lumpy and gray. They can – are low, lumpy and gray. They can look like cells under a microscope.look like cells under a microscope.

• NimbostratusNimbostratus – dark gray with a “ragged” base. They – dark gray with a “ragged” base. They are associated with continuous rain or snow.are associated with continuous rain or snow.

Clouds with Vertical GrowthClouds with Vertical Growth(“Cumu”)(“Cumu”)

• Surface – 13 000mSurface – 13 000m• These clouds grow These clouds grow

high up into the high up into the atmosphere rather atmosphere rather than spreading out.than spreading out.

• CumulusCumulus – cloud puffs – cloud puffs that are about the that are about the size of your fist when size of your fist when you hold up your you hold up your hand at arm’s length.hand at arm’s length.

• CumulonimbusCumulonimbus – – thunderstorm cloudsthunderstorm clouds