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Weather & Climate Basics

Weather vs. ClimateWeather FrontsSevere Weather

Orographic LifitngGlobal Winds

El Nino/La Nina

Weather vs. Climate

Weather

• Day to day physical conditions in the lower troposphere (temperature, humidity, wind, etc.)

Climate

• Long-term weather patterns for a region

• Impacted by– Latitude—inverse

relationship between latitude and solar intensity

– Topographic Effects—land vs. water; mountain vs. valley

– Air masses—origin

Air Masses

mP - maritime polar air mass cT - continental tropical air mass

mT - maritime tropical air mass cP - continental polar air mass

mE - maritime Equatorial air mass cA - continental artic air mass

Weather Fronts

• Boundary between 2 dissimilar air masses.

• Cold Front: cold air pushes warm air out; thunderstorms along the front; brings in cooler, drier air

• Warm Front: warm air pushes cold air out; brings in warm, moist air

• Stationary Front: warm and cold air meet but cannot displace one another; slow to move out

• Occluded Front: cyclogenesis process - cold front overtakes a warm front. Warm air is wedged upward between two cold fronts.

Types of Fronts

Midlatitude Cyclone

High vs. Low Pressure Systems

High: winds moving down and outward

Low: winds moving inward and upward

High pressure system:Clear skies and light winds

Low pressure system:Cloudy with precipitation likely

Severe Weather - Thunderstorms

Severe Weather - Tornado

Monsoon Season in India

Rain Shadows

Death Valley, CA

Orographic Lifting & Rain Shadows

14

Global Winds

• Wind = air in motion• Caused by

– Pressure differences—combination of solar radiation vs. latitude and density)

– Coriolis effect—deflection of fluid (including air) due to Earth’s rotation; N. hemisphere/clockwise, S. hemisphere/counterclockwise

– Topography—orographic lifting; differential heating of land vs. water

• Patterns fluctuate with seasons

Atomspheric Circulation

Hadley Cells

Global Air Circulation: 3-Cell Model

Global Air Circulation: 3-Cell Model

• Idealized model: Ferrel & Polar cells are poor representations of actual winds.

• Continents & topographic irregularities cause significant real-world variations

Geologic effects on climate

El Nino

La Nina