Chapter 8 - Weather Short-term day-to-day condition of the...

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1 Chapter 8 Weather Weather Short-term day-to-day condition of the atmosphere Snapshot of atmospheric conditions A technical report of the Earth-atmosphere heat energy budget Long-term average conditions over the decades and extremes in a region? Weather Temperature Air pressure Relative humidity Wind speed and direction Seasonal factors – insolation receipt Humidity Water vapor in the air The capacity of the air for water vapor f (temperature of air, temperature of water vapor) How do we express humidity? Three States of Water Humidity Relative humidity Tells us about how near the air is to saturation The amount of water vapor in the air Relative humidity = x 100 The maximum possible water vapor in the air <100% Æ evaporation exceeds condensation = 100% Æ evaporation = condensation : SATURATION
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2 Relative Humidity Evaporation vs. condensation @ 5 p.m., 11 a.m., and 5 a.m.? Weather Air Masses Atmospheric lifting mechanisms Midlatitude Cyclonic systems Violent weather Air Masses Earth’s surface imparts its temperature & moisture characteristics to the air it touches The effect of the surface on the air Regional masses of air Temperature Humidity Stability These masses interact to produce weather patterns Air Masses Air Stability The tendency for air to rise or fall through the atmosphere under its own "power“ Stable air has a tendency to resist movement Unstable air will easily rise Temperature change Air Mass The distinctive body of air Reflect the characteristics of its source region Cold Canadian air mass Moist tropical air mass Homogeneous mix of temperature and humidity Sometimes extends through the lower half of the troposphere Possesses all the physical characteristics of the atmosphere Link the Earth-atmosphere energy budget Link water – weather systems Air Masses effecting North America Moisture m : maritime (wet) c : continental (dry) Temperature – latitude factor A : Arctic P : Polar T : Tropical E : Equatorial AA : Antarctic
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3 Principal Air Masses of North America Sea-surface temperatures are in o C SH : Specific humidity ( the ratio of water vapor to dry air in a particular volume) Continental Polar (cP) Form only in the Northern Hemisphere Most developed in winter In mid-and high-latitude weather The cold, dense cP air lifts moist, warm air in its path Lifting, cooling, and condensation Cool, dry, high pressure, stable, clear skies Maritime Polar (mP) Northwest and Northeast Cool, moist, unstable
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This note was uploaded on 03/25/2008 for the course GEOG 203 taught by Professor Guneralph during the Spring '08 term at Texas A&M.

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Chapter 8 - Weather Short-term day-to-day condition of the...

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