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Weather & Climate Basics Weather vs. Climate Weather Fronts Severe Weather Orographic Lifitng Global Winds El Nino/La Nina
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
Monsoon Season in India
Rain Shadows
Orographic Lifting & Rain Shadows
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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
