Weather ForecastsWeather Forecasts

Weather Dynamics UnitWeather Dynamics Unit

Science 10Science 10

Mrs. S. Pipke-PainchaudMrs. S. Pipke-Painchaud

Weather ForecastsWeather Forecasts

How do we predict the weather now? How do we predict the weather now?

How did people predict weather in the How did people predict weather in the past?past?

(Nelson Science 10 543)(Nelson Science 10 543)

Meteorology:Meteorology: ““the study of the ___________ and weather the study of the ___________ and weather

forecasting” (NS10 543)forecasting” (NS10 543)__________________:__________________:

People who study weather and work in this People who study weather and work in this field.field.

Meteor (Greek) Meteor (Greek) high in the air high in the air

North American Weather SystemsNorth American Weather Systems

______________:______________: Humid and hot, cloudy with sunshineHumid and hot, cloudy with sunshine

North Pole:North Pole: __________ and _______________________ and _____________

Mid-Latitudes are harder to predictMid-Latitudes are harder to predict Weather System:Weather System:

““a set of _____________, wind, _____________, and a set of _____________, wind, _____________, and ______________ conditions for a certain region that ______________ conditions for a certain region that moves as a unit for a period of days” (NS10 546).moves as a unit for a period of days” (NS10 546).

Mid-Latitude areas: air masses move west to east Mid-Latitude areas: air masses move west to east (mid-latitude westerly winds)(mid-latitude westerly winds)

NS10 546NS10 546

Air MassesAir Masses ““a _____________ body of air in which the a _____________ body of air in which the

______________ and __________ content at a ______________ and __________ content at a specific altitude are fairly ______________” specific altitude are fairly ______________” (NS10 546).(NS10 546). _______kms across_______kms across Form where air is relatively stable for days or weeks.Form where air is relatively stable for days or weeks.

i.e. Cold polar air from the north is ___________ and cold i.e. Cold polar air from the north is ___________ and cold because little evaporation occurs in the atmosphere (sun’s because little evaporation occurs in the atmosphere (sun’s rays are at a low angle)rays are at a low angle)

i.e Warm air from the ocean brings ________ and i.e Warm air from the ocean brings ________ and precipitation.precipitation.

Air masses mix via ____________ and Air masses mix via ____________ and _______________ winds._______________ winds.

Cold air moves southCold air moves south Warm air moves northWarm air moves north

NS10 546NS10 546

Low-Pressure SystemsLow-Pressure Systems ___________ skies, ________ weather ___________ skies, ________ weather

(cyclone - counterclockwise)(cyclone - counterclockwise) Refer to page 547 for the stages of a stormRefer to page 547 for the stages of a storm

http://en.wikipedia.org/wiki/Image:Low_pressure_system_over_Iceland.jpg

http://nsidc.org/arcticmet/factors/pressure.html

Stationary FrontStationary Front

When the boundary between a cold and warm When the boundary between a cold and warm front remains ________________ for a period of front remains ________________ for a period of time = ________________________ weather time = ________________________ weather until the air begins to moveuntil the air begins to move

NS10 548NS10 548

High Pressure SystemsHigh Pressure Systems

__________________ – high pressure __________________ – high pressure system (clockwise)system (clockwise)

_____________ skies_____________ skiesDuring the Canadian winter, we experience During the Canadian winter, we experience

cold high pressure systems. The high atm cold high pressure systems. The high atm pressure near the surface occurs as a result pressure near the surface occurs as a result of cold, dry, descending arctic air. Dry air of cold, dry, descending arctic air. Dry air generally brings clear skies.generally brings clear skies.

(NS10 548)(NS10 548)

Regional WeatherRegional Weather

Influence globally by:Influence globally by: __

Conditions that affect weather in a Conditions that affect weather in a localized area.localized area.

i.e. shore of a lakei.e. shore of a lakeBeside a mountain rangeBeside a mountain range

ThermalsThermals

An updraft ~ local _______________- An updraft ~ local _______________- currentcurrent

Sun’s energy heats the ground, the _________ Sun’s energy heats the ground, the _________ ground heats the air above it, warm less dense air ground heats the air above it, warm less dense air ____________. The air that moves upward leaves ____________. The air that moves upward leaves a space for cooler less dense air to move in at the a space for cooler less dense air to move in at the base. i.e. a local convection currentbase. i.e. a local convection current

NS10 553NS10 553

Sea BreezesSea Breezes A thermal formed near an _________ or ___________.A thermal formed near an _________ or ___________. Land heats and cools ____________ than water.Land heats and cools ____________ than water.

Warm air near land moves out over the cool water and the cool air Warm air near land moves out over the cool water and the cool air over the water moves in over the land (local convection current).over the water moves in over the land (local convection current).

i.e. ____________ near the lake in the summeri.e. ____________ near the lake in the summer i.e. ____________ near the lake in the winteri.e. ____________ near the lake in the winter

Land Breeze: Land Breeze: A thermal flowing from ____________ to ____________ A thermal flowing from ____________ to ____________ Occurs in the evening (water is warm so air rises and is replaced Occurs in the evening (water is warm so air rises and is replaced

by the cooler air from the land).by the cooler air from the land). ______________ breezes______________ breezes

NS10 554NS10 554

Lake – Effect SnowLake – Effect Snow

Air moves across a warm lake in the Air moves across a warm lake in the winter and picks up _________________.winter and picks up _________________.

When it reaches the cool land on the other When it reaches the cool land on the other side it _____________.side it _____________.

Cities on the leeward or downwind side of the Cities on the leeward or downwind side of the lake will receive _____________ snow.lake will receive _____________ snow.

NS10 554NS10 554

Chinook WindsChinook Winds Occurs ________ of the rocky mountainsOccurs ________ of the rocky mountains ____________, ___________ wind____________, ___________ wind Wind on the west side of the mountains undergoes Wind on the west side of the mountains undergoes

orographic lifting, which causes the water vapour to orographic lifting, which causes the water vapour to ____________ = ____________.____________ = ____________.

Condensation = ___________ release = __________ airCondensation = ___________ release = __________ air Air on the east side of the mountains is dry, but warm = Air on the east side of the mountains is dry, but warm =

increase in local temperatures.increase in local temperatures. ““on January 6, 1966, chinook winds raised the temperature in on January 6, 1966, chinook winds raised the temperature in

parts of Alberta by 21 Celsius degrees in only 4 minutes” (NS10 parts of Alberta by 21 Celsius degrees in only 4 minutes” (NS10 554).554).

NS10 555NS10 555

HumidityHumidity

““a measure of the ____________ of water a measure of the ____________ of water vapour in the ____________. . . (also vapour in the ____________. . . (also called absolute humidity)” (NS10 558).called absolute humidity)” (NS10 558).

Relative Humidity:Relative Humidity: ““a measure of the amount of water vapour a measure of the amount of water vapour

_______________ in the air as a _______________ in the air as a _________________ of the maximum amount _________________ of the maximum amount of water vapour the air could hold at that of water vapour the air could hold at that temperature” (NS10 558).temperature” (NS10 558).

______________ Air:______________ Air: Relative humidity = 100%Relative humidity = 100% Air is holding the max mass of water vapourAir is holding the max mass of water vapour Clouds or ____________ formClouds or ____________ form Precipitation occursPrecipitation occurs

_____________ _____________ Forms when at a 100% relative humidityForms when at a 100% relative humidity Dew Point: temp at which dew formsDew Point: temp at which dew forms i.e. condensation occurs when vapour from the air comes into i.e. condensation occurs when vapour from the air comes into

contact with a surface temperature at or below the dew point.contact with a surface temperature at or below the dew point. The outside of a glass, the mirror in the bathroom, etc.The outside of a glass, the mirror in the bathroom, etc.

NS10 559NS10 559

Effects of HumidityEffects of HumidityFormation of dewFormation of dewSweat:Sweat:

________________ of water from your body ________________ of water from your body = ______________ the body= ______________ the body

___________ humidity = slower evaporation = ___________ humidity = slower evaporation = you feel _________________you feel _________________

Cold temperature contain less water Cold temperature contain less water vapour vapour therefore, home, school or office therefore, home, school or office air has less humidity and feels dry.air has less humidity and feels dry.

What technology do people use to add humidity to What technology do people use to add humidity to the air?the air?

(NS10 560)(NS10 560)

SourcesSources

Nelson Science 10 Textbook Chapter 14Nelson Science 10 Textbook Chapter 14