CEE 1030 1nd Edition Lecture 22 Atmosphere Outline of Last Lecture I Salinity II Movement of ocean water III Ocean zones IV Seawater density V Tidal currents VI Review Outline of Current Lecture I Origin of Earth s atmosphere II Atmosphere layers III Atmospheric pressure IV Weather fronts V Clouds and precipitation VI Global wind patterns Current Lecture I II III Origin of Earth s atmosphere a Gases trapped in planet s interior released by volcanic eruptions b Ancient atmosphere consisted mainly of water vapor and carbon dioxide c Atmosphere the layer of gases surrounding the planet retained by gravity d Now the atmosphere consists of 78 nitrogen and 21 oxygen Atmosphere layers a 90 of gases concentrated in troposphere b Denser gases sink so composition varies with altitude c Troposphere stratosphere mesosphere thermosphere exosphere d No distinct upper limit the atmosphere gradually thins and fades into space e Ozone layer i Layer in stratosphere with high concentration of ozone molecules ii Absorbs ultraviolet light Atmospheric pressure a Barometric pressure force per unit are exerted by atmosphere on the surface beneath or within it b Pressure decreases as altitude increases c Air in the troposphere i Warm air is less dense than cold air These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV V ii Moving air parcels displace others resulting in atmospheric convection d Coastal breezes i On coasts prevailing wind direction changes from day to night because of temperature differences in air over water and land ii Sea breeze during the day air moves from sea onto land iii Land breeze during the night air moves from land out to sea e Atmospheric convection i Moving air mass creates a low pressure zone where it began and high pressure zone where it is going ii Cloud formation 1 Convectional lifting air mass at Earth s surface is warmed and rises then expands and cools at higher altitudes forming clouds 2 Adiobatic cooling when air rises pressure decreases and air parcel is allowed to expand resulting in cooling a If rising air is moist then water vapor condenses to water droplets as air parcel cools Weather fronts a Front transition zone between air masses of different densities b Fronts extend both horizontally and vertically and are often marked by cloud formation Clouds and precipitation a Cloud a visible mass of condensed water droplets or ice crystals suspended in the atmosphere b Clouds form when moist air reaches saturation point c Types of clouds i Clouds are differentiated by their altitude and whether they are layered or convective d Cloud formation i Frontal lifting convergence of air masses fronts ii Warmer moister air mass will override cooler dryer air masses iii Radiative cooling when the sun sets and no longer warms the air and ground air just above the ground cools forming fog e Precipitation i Precipitation condensation of atmospheric water vapor that falls to Earth s surface ii Liquid precipitation 1 Rain or drizzle differentiated by droplet size forms when separate drops of water fall to Earth s surface iii Frozen precipitation 1 Forms when atmospheric water is cooled below its freezing point 2 When it comes into contact with dust particles supercooled water condenses around the nucleus VI iv Freezing precipitation 1 As it falls crystal moves through warm air layer and melts completely but then encounters colder air and is supercooled v Thunderstorms form when air mass with significant condensation is forced upward rapidly in unstable atmosphere where the temperature drops 1 Lightning atmospheric discharge of electricity resulting from differently charged particles in air masses vi Tornado a small cyclone with very strong winds typically has tube like condensation funnel extending from rotating cloud base to the ground 1 The more different the density of the air masses the more turbulent the weather front 2 Sudden changes n wind direction or speed causes air mass to spin 3 Updrafts created by the thunderstorm tilt spinning air mass upward 4 Fujita scale wind speed etc based on tornado damage vii Cyclone low pressure system with inward spiraling winds created by converging fronts Global wind patterns a Convection circulates air by the unequal warming at different latitudes i At poles dense cool air descends and moves toward the equator ii At equator less dense warm air rises b Variation in moisture levels resulting from evaporation and condensation patterns cause cool dry air to sink at 30 degrees N and 30 degrees S of equator c Coriolis effect deflects air currents to the right in the northern hemisphere and to the left in the southern hemisphere d Jet streams fast narrow air currents found near the stratosphere troposphere transition caused by atmospheric heating and planet s rotation on the axis e Seasonal changes in solar heating of Earth s surface affects distribution of high and low pressure areas f Monsoon heavy rainy season that lasts for several months with lasting climatic effects g Water retains heat better than air i Temperature varies more in continental interiors than on coasts ii Large bodies of water moderate temperature variation