Weather, Seasons, & Climate Global convection currents: movement of air between the equator and poles, caused by temperature differences, that produce global wind patterns. Coriolis Effect: The way Earth’s rotation makes winds in the Northern Hemisphere curve to the right (eastward) and winds in the Southern Hemisphere curve to the left. (westward).

Global Atmospheric Wind Patterns: Doldrums: near equator, a calm area where warm air rises Tradewinds: blow from the horse latitudes (calm areas of falling air) toward the equator Horse Latitudes: areas of calm where cool air sinks at the tropics Prevailing Westerlies: blow away from the horse latitudes toward the poles Polar Easterlies: cold polar air blowing away from the poles

Air Masses affect weather and climate. Maritime Polar: cool moist air from over polar water Maritime Tropical: warm moist air from over tropical water Continental Polar: cold dry air from over polar land Continental Tropical: hot dry air from over tropical land Arctic: cold dry air, receives little solar radiation in winter, but near constant solar radiation in summer.

Fronts affect weather Cold Front: cold air moves under warmer air – storms Warm Front: warm air moves over colder air – light precipitation, followed by warm/dry weather Occluded Front: cold & cool air masses come together & force warm air up – light precipitation Stationary Front: stays in one place for extended time.

High and Low Pressure Areas: H=dry weather; L=wet weather. Winds are caused by differences in pressure due to the imbalanced heating of Earth’s surface. High and Low Pressure Areas: H=dry weather; L=wet weather.

Weather: the current atmospheric phenomena of an area Humidity is the amount of water vapor in the atmosphere at a given temperature Clouds form as water vapor condenses on condensation nuclei (particulates of dust, smoke, or ash) as the air cools. Precipitation: H2O falling to Earth as rain, snow, sleet, hail.

Severe Weather 46% of all weather related US deaths are from cold. 2000+ per year

28% of all weather related US deaths are from heat. Severe Weather 28% of all weather related US deaths are from heat. 650+ deaths per year

Severe Weather Thunderstorms – severe storm of thunder, lightning, heavy rain and/or hail. Flooding – temporary rise in water level when the ground can’t soak up rainfall fast enough. 7% of weather related deaths in US; 200+ deaths per year. Lightning – static electric discharge between clouds & Earth. Temperature can exceed 50,000 ̊F. 50+ deaths in deaths per year in US. Lightning – Thunder ratio to determine distance. Seconds from flash divided by 5 = miles. Ex: 10s ÷ 5 = 2 miles away

Severe Weather Tornadoes – a rotating column of air from thunderclouds. 4% of weather related deaths in US; 80+ per year Hurricanes – storm with violent winds, flooding, and storm surges produced by tropical cyclones. 89% of deaths are from storm surge & flooding.

Weather Forecasting Maps

Seasons are caused by the tilt of the Earth on its axis Seasons are caused by the tilt of the Earth on its axis. Seasons are NOT caused by distance from the Sun.

Climate: typical weather pattern in an area over a long period of time Main factors that influence temperature: - distance from large bodies of water (water holds heat and keep coastal areas more moderate, in-land areas have wider temperature extremes) - ocean currents (currents from the equator bring warm air, from poles bring cold air) - latitude (distance from the equator) - altitude (elevation above sea level)

Main factors that affect precipitation are prevailing winds & the presence of mountains -Mountain Effects on Climate: * Windward: water vapor condenses in rising air on windward side of the mountain chain producing precipitation. Produces a very moist climate * Leeward: dry air moves over the top of the mountain chain producing a very dry climate.

Major Climate Zones: Tropical Rainforest: wet, over 100 inches precipitation, 70 – 80 ºF. Desert: dry, less than 10 inches precipitation, hot, up to 120 ºF. Grassland: moist, 10 – 30 inches precipitation, cold winters & hot summers, -40 – 110 ºF. Temperate Marine (mediteranean/subtropical): moist, 20 – 50 inches precipitation, moderate temps, 40 – 90 ºF. Deciduous Forest (temperate continental): moist, 20 – 40 inches precipitation, cold winters & hot summers, -20 – 100 ºF. Coniferous Forest (taiga/boreal forest): moist, 20 – 30 inches precipitation, cool climate, -30 – 70 ºF. Tundra (permafrost): moist, 10 – 20 inches of precipitation, cold, -70 – 55 ºF. Highlands: mountainous regions with similar climates to tundra. Polar: permanently covered in ice