Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

Learning Targets: I can discuss key functions that the atmosphere serves that enables life to exist on Earth. I can explain factors that cause the dynamic balance in the atmosphere to change. I can model and explain the relationships and energy flow existing in various Earth systems (atmosphere).

46.What is an air parcel? An air parcel is a block of air with uniform temperature and pressure throughout 47.In what 4 ways can the air parcel change over time? The air parcel can change over time by rising, falling, or emitting or absorbing heat. Photo: Pamela R. Cox 2013 Along Bluegrass Parkway, Kentucky

48. If the pressure of the surrounding environment changes, the pressure of the parcel changes, but it does not exchange heat or chemicals with the surroundings and therefore may behave differently from its surroundings. Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

49.Many weather patterns start with rising air. 50.Air does not rise simply because it is warm. Rather, air that becomes warmer than its surroundings becomes buoyant and floats on top of cooler, denser air in the same way that oil floats on top of water. This buoyant motion is called convection. Photo: Pamela R. Cox 2013 Along Bluegrass Parkway, Kentucky

51.This is also a key factor in weather and climate. water 52. What percent of the atmosphere typically consists of water vapor? 52. What percent of the atmosphere typically consists of water vapor? two to three percent Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

53.What does relative humidity compare? the amount of water vapor in the air to the maximum amount that air can hold at that temperature 54. When relative humidity reaches 100 percent, the air has reached saturation pressure and cannot absorb any more water vapor. 55. Why do high humidity levels make people feel uncomfortable? because little or none of their sweat can evaporate and draw heat from their skin. Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

56. As air warms, the amount of water vapor that it can hold rises exponentially. Consequently, atmospheric water vapor concentrations are highest in warm regions and decrease toward the poles Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

Atmospheric water vapor mean,

57.Discuss three ways atmospheric water vapor contributes to weather patterns. 1.adding water vapor to the air reduces its density, so adding moisture to dry air may make it become buoyant and rise. 2.moist air carries latent energy, the potential for condensation of water vapor to heat the air. 3.When an air parcel cools to its dew point, water vapor begins condensing and forming cloud droplets or ice crystals, which may ultimately grow large enough to fall as rain or snow.

58. Define latent energy. the potential for condensation of water vapor to heat the air 59.Define dew point. denotes the temperature to which air would have to cool to reach 100 percent relative humidity Photo: Pamela R. Cox 2013 Lexington, Kentucky

60.Explain what determines whether atmospheric conditions can be stable or unstable. How quickly the temperature of the environment declines with altitude determines stability of the atmosphere.An unstable atmosphere is more likely to produce clouds and How quickly the temperature of the environment declines with altitude determines stability of the atmosphere. An unstable atmosphere is more likely to produce clouds and storms than a stable atmosphere Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

Conditional instability

61. Convection is not the only process that lifts air from lower to higher altitudes. When winds run into mountains and are forced upward the air cools, often forming clouds over windward slopes and the crests of hills. Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky

62. Define and explain convergence. Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky Convergence occurs when air masses run together, pushing air upward generating thunderstorms. And when warm and cold air fronts collide, the denser cold air slides underneath the warm air layer and lifts it.

63. Compare and contrast low-altitude clouds with high-altitude clouds Photo: Pamela R. Cox 2013 Elizabethtown, Kentucky Low-altitude clouds emit and absorb infrared radiation much as the ground does, so they are roughly the same temperature as Earth's surface and thus do not increase atmospheric temperatures Low-altitude clouds emit and absorb infrared radiation much as the ground does, so they are roughly the same temperature as Earth's surface and thus do not increase atmospheric temperatures. High-altitude clouds tend to be thinner, so they do not reflect significant levels of incoming solar radiation.They efficiently High-altitude clouds tend to be thinner, so they do not reflect significant levels of incoming solar radiation. They efficiently absorb outgoing thermal radiation and warm the atmosphere, and they radiate heat back to the surface.