Presentation on theme: "Warm Up 3/14 Which gas is most important for understanding atmospheric processes? a. water vapor c. carbon dioxide b. oxygen d. ozone What is true."— Presentation transcript:
1 Warm Up 3/14Which gas is most important for understanding atmospheric processes?a. water vapor c. carbon dioxideb. oxygen d. ozoneWhat is true about warm, saturated air?a. It contains less water vapor than cold air.b. It contains more water vapor than cold air.c. It does not contain any water vapor.d. It contains the same amount of water vapor as cold air.If the water-vapor content of air remains constant, lowering air temperature causes a(n) ____.a. decrease in relative humidityb. increase in relative humidityc. increase in evaporationd. temperature inversionAnswers: 1) a. 2) b. 3) b.
3 Air Compression and Expansion Temperature changes that happen even though heat isn’t added or subtracted are called adiabatic temperature changesWhen air is allowed to expand, it cools, and when it is compressed, it warmsAny time a volume of air moves upward, it passes through regions of successive lower pressureDry Adiabatic Rate – the rate of adiabatic warming or cooling in unsaturated air (1ºC/100 m)Wet Adiabatic Rate – the rate of adiabatic temperature change in saturated air; it is always less than the dry adiabatic rate
5 Concept CheckWhat happens to heat stored in water vapor when it is cooled to its dew point?Latent heat is released.
6 Orographic Lifting and Frontal Wedging Four mechanisms that can cause air to rise are orographic lifting, frontal wedging, convergence, and localized convective liftingOrographic Lifting – mountains acting as barriers to the flow of air, forcing the air to ascendMany of the rainiest places on Earth are located on windward mountain slopesBy the time the air has reached the leeward side of the mountain, much of its moisture has been lostFront – the boundary between two adjoining air masses having contrasting characteristicsThe cooler denser air acts as a barrier over which the warmer, less dense air rises
9 Convergence and Localized Convective Lifting Whenever air in the lower atmosphere flows together, lifting results, this is called convergenceThis leads to adiabatic cooling and possibly cloud formationOn warm summer days, unequal heating of Earth’s surface may cause pockets of air to be warmed more than the surrounding airConsequently, this warmer, less dense packet will move upwardThese rising parcels of warmer air are called thermalsThe process that produces rising thermals is localized convective liftingWhen warm parcels rise above the condensation level, clouds form
12 Concept Check What are thermals? Thermals are rising parcels of air that are warmer than surrounding air.
13 StabilityStable air is any air which resists vertical movement due to density differencesStable air tends to remain in its original position, while unstable air tends to riseAir stability is determined by measuring the temperature of the atmosphere at various heightsThe rate of change of air temperature with height is called the environmental lapse rateTemperature Inversion – a layer where the temperature increases with height; the most stable conditions for airClouds associated with the lifting of unstable air are towering and often generate thunderstorms and tornados
18 Concept Check What types of weather can result when stable air rises? Clear weather may occur or light-to-moderate precipitation.
19 CondensationRecall that condensation happens when water vapor in the air changes to a liquid in the form of dew, fog, or cloudsFor any of the forms of condensation to occur, the air must be saturatedGenerally, there must be a surface for water vapor to condense onCondensation Nuclei – tiny bits of particulate matter that serve as surfaces on which water vapor condensesWhen condensation takes place, the initial growth rate of cloud droplets is rapidIt diminishes quickly because the excess water vapor is absorbed by numerous competing particlesThis results in the formation of a cloud consisting of millions upon millions of tiny water droplets