Weather Forecasts Weather Dynamics Unit Science 10 Mrs. S. Pipke-Painchaud

Weather Forecasts How do we predict the weather now? How do we predict the weather now? How did people predict weather in the past? How did people predict weather in the past? (Nelson Science ) (Nelson Science )

Meteorology: Meteorology: “the study of the ___________ and weather forecasting” (NS10 543) “the study of the ___________ and weather forecasting” (NS10 543) __________________: __________________: People who study weather and work in this field. People who study weather and work in this field. Meteor (Greek)  high in the air Meteor (Greek)  high in the air

North American Weather Systems ______________: ______________: Humid and hot, cloudy with sunshine Humid and hot, cloudy with sunshine North Pole: North Pole: __________ and _____________ __________ and _____________ Mid-Latitudes are harder to predict Mid-Latitudes are harder to predict Weather System: Weather System: “a set of _____________, wind, _____________, and ______________ conditions for a certain region that moves as a unit for a period of days” (NS10 546). “a set of _____________, wind, _____________, and ______________ conditions for a certain region that moves as a unit for a period of days” (NS10 546). Mid-Latitude areas: air masses move west to east (mid-latitude westerly winds) Mid-Latitude areas: air masses move west to east (mid-latitude westerly winds) NS NS10 546

Air Masses “a _____________ body of air in which the ______________ and __________ content at a specific altitude are fairly ______________” (NS10 546). “a _____________ body of air in which the ______________ and __________ content at a specific altitude are fairly ______________” (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 because little evaporation occurs in the atmosphere (sun’s rays are at a low angle) i.e. Cold polar air from the north is ___________ and cold because little evaporation occurs in the atmosphere (sun’s rays are at a low angle) i.e Warm air from the ocean brings ________ and precipitation. i.e Warm air from the ocean brings ________ and precipitation. Air masses mix via ____________ and _______________ winds. Air masses mix via ____________ and _______________ winds. Cold air moves south Cold air moves south Warm air moves north Warm air moves north NS NS10 546

Low-Pressure Systems ___________ skies, ________ weather (cyclone - counterclockwise) ___________ skies, ________ weather (cyclone - counterclockwise) Refer to page 547 for the stages of a storm Refer to page 547 for the stages of a storm ow_pressure_system_over_Iceland.jpg ssure.html

Stationary Front When the boundary between a cold and warm front remains ________________ for a period of time = ________________________ weather until the air begins to move When the boundary between a cold and warm front remains ________________ for a period of time = ________________________ weather until the air begins to move NS NS10 548

High Pressure Systems __________________ – high pressure system (clockwise) __________________ – high pressure system (clockwise) _____________ skies _____________ skies During the Canadian winter, we experience cold high pressure systems. The high atm pressure near the surface occurs as a result of cold, dry, descending arctic air. Dry air generally brings clear skies. During the Canadian winter, we experience cold high pressure systems. The high atm pressure near the surface occurs as a result of cold, dry, descending arctic air. Dry air generally brings clear skies. (NS10 548)

Regional Weather Influence globally by: Influence globally by: _ Conditions that affect weather in a localized area. Conditions that affect weather in a localized area. i.e. shore of a lake i.e. shore of a lake Beside a mountain range Beside a mountain range

Thermals An updraft ~ local _______________- current An updraft ~ local _______________- current Sun’s energy heats the ground, the _________ ground heats the air above it, warm less dense air ____________. The air that moves upward leaves a space for cooler less dense air to move in at the base. i.e. a local convection current Sun’s energy heats the ground, the _________ ground heats the air above it, warm less dense air ____________. The air that moves upward leaves a space for cooler less dense air to move in at the base. i.e. a local convection current NS NS10 553

Sea 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 over the water moves in over the land (local convection current). 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). i.e. ____________ near the lake in the summer i.e. ____________ near the lake in the summer i.e. ____________ near the lake in the winter i.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 by the cooler air from the land). Occurs in the evening (water is warm so air rises and is replaced by the cooler air from the land). ______________ breezes ______________ breezes NS NS10 554

Lake – Effect Snow Air moves across a warm lake in the winter and picks up _________________. Air moves across a warm lake in the winter and picks up _________________. When it reaches the cool land on the other side it _____________. When it reaches the cool land on the other side it _____________. Cities on the leeward or downwind side of the lake will receive _____________ snow. Cities on the leeward or downwind side of the lake will receive _____________ snow. NS NS10 554

Chinook Winds Occurs ________ of the rocky mountains Occurs ________ of the rocky mountains ____________, ___________ wind ____________, ___________ wind Wind on the west side of the mountains undergoes orographic lifting, which causes the water vapour to ____________ = ____________. Wind on the west side of the mountains undergoes orographic lifting, which causes the water vapour to ____________ = ____________. Condensation = ___________ release = __________ air Condensation = ___________ release = __________ air Air on the east side of the mountains is dry, but warm = increase in local temperatures. Air on the east side of the mountains is dry, but warm = increase in local temperatures. “on January 6, 1966, chinook winds raised the temperature in parts of Alberta by 21 Celsius degrees in only 4 minutes” (NS10 554). “on January 6, 1966, chinook winds raised the temperature in parts of Alberta by 21 Celsius degrees in only 4 minutes” (NS10 554). NS NS10 555

Humidity “a measure of the ____________ of water vapour in the ____________... (also called absolute humidity)” (NS10 558). “a measure of the ____________ of water vapour in the ____________... (also called absolute humidity)” (NS10 558). Relative Humidity: Relative Humidity: “a measure of the amount of water vapour _______________ in the air as a _________________ of the maximum amount of water vapour the air could hold at that temperature” (NS10 558). “a measure of the amount of water vapour _______________ in the air as a _________________ of the maximum amount of water vapour the air could hold at that temperature” (NS10 558).

______________ Air: ______________ Air: Relative humidity = 100% Relative humidity = 100% Air is holding the max mass of water vapour Air is holding the max mass of water vapour Clouds or ____________ form Clouds or ____________ form Precipitation occurs Precipitation occurs _____________ _____________ Forms when at a 100% relative humidity Forms when at a 100% relative humidity Dew Point: temp at which dew forms Dew Point: temp at which dew forms i.e. condensation occurs when vapour from the air comes into contact with a surface temperature at or below the dew point. i.e. condensation occurs when vapour from the air comes into 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. NS NS10 559

Effects of Humidity Formation of dew Formation of dew Sweat: Sweat: ________________ of water from your body = ______________ the body ________________ of water from your body = ______________ the body ___________ humidity = slower evaporation = you feel _________________ ___________ humidity = slower evaporation = you feel _________________ Cold temperature contain less water vapour  therefore, home, school or office air has less humidity and feels dry. Cold temperature contain less water vapour  therefore, home, school or office air has less humidity and feels dry. What technology do people use to add humidity to the air? What technology do people use to add humidity to the air? (NS10 560) (NS10 560)

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