Warm Up 1. At 25 0 C, air contains 15 gH 2 O / m 3 air. Saturation point: 20 g/m 3 Calculate the relative humidity. 2. What is the dry adiabatic rate? 3. How does the temperature change within the thermosphere?

WARM UP 1. What is the most abundant gas in the atmosphere? 2. What causes different layers in the atmosphere to form? 3. What is used to measure atmospheric pressure? 4. Where is the ozone layer located?

Chapters 17 and 18

Chapter 17: Atmosphere  ATMOSPHERE - layer of gases and tiny particles surrounding the earth  WEATHER - general atmospheric conditions at a particular time and place  CLIMATE - general weather conditions over many years

Composition of the Atmosphere  Elements: NITROGEN (N 2 ) OXYGEN (O 2 ) ARGON (Ar)  Compounds: CARBON DIOXIDE (CO 2 ) WATER (H 2 O) OZONE (O 3 )  absorbs harmful UV RAYS (ultraviolet)

Composition of the Atmosphere  Atmospheric Dust: SOIL ASH MICROBES CRYSTALS Ca Carbon Dioxide Nitrogen ARGON All Others Oxygen

Atmospheric Pressure  Gravity that is PULLING particles TOWARD EARTH  Ratio of: air weight. surface area on which it presses  Measuring Device for Atmospheric Pressure: BAROMETER (p.532)  Atm.Pressure measured in N/m 2.  1 Atm = 760 mmHg

Atmospheric Pressure  Δ Pressure:Higher altitude = FEWER gases = LOWER pressure  Lower altitude = MORE gases = HIGHER pressure  Δ Temperature: Higher altitude = LOWER pressure = LOWER temperature  Lower altitude = HIGHER pressure = HIGHER temperature

Atmospheric Layers  Atmospheric Layering is caused by TEMPERATURE differences.

Atmospheric Layers  (1) TROPOSPHERE  Closest to earth  Holds the most CO 2 and H 2 O vapor  All WEATHER changes happen here  Temperature ↓ as altitude increases.  Why? FARTHER FROM THE HEAT ABSORBED BY EARTH

 2) STRATOSPHERE  From tropopause to 50km in altitude  Includes the OZONE LAYER (O 3 )  Temperature ↑ as altitude increases.  Why? CLOSER TO O 3 LAYER WHICH ABSORBS UV LIGHT & HEAT

 3) MESOSPHERE  From stratopause to 80km in altitude  Coldest layer  Temperature ↓ as altitude increases.  Why? FARTHER FROM O 3 LAYER

 (4) THERMOSPHERE  From mesopause to outer space  Temperature ↑ as altitude increases.  Why? OXYGEN AND NITROGEN ABSORB SHORT-WAVE, HIGH-ENERGY SOLAR RADIATION

 Two layers:  IONOSPHERE - lower layer.  Holds electrically charged particles.  EXOSPHERE - upper layer.  Holds light gases (helium/hydrogen).  No clear boundary between exosphere and space…  Air gets thinner and thinner until you’re in outer space.

Atmospheric Moisture  3 forms of water: ICE, LIQUID, or WATER VAPOR (most is in VAPOR form)  Phase Changes: HEAT energy causes an INCREASE in molecular motion. *Motion causes molecular COLLISIONS and energy transfer.

 Evaporation: molecules speed up and change from a LIQUID to WATER VAPOR  Condensation: molecules slow down and change from a GAS to a LIQUID.  Sublimation: SOLIDS change directly to a GAS. (Ex: DRY ICE)  Deposition: GASES change directly to a SOLID. (Ex: FROST)

 Humidity = AMOUNT OF WATER VAPOR IN AIR  SATURATED = air contains all of the water vapor it can hold.  When saturated, WARM air can hold more water vapor than COLD air.  Measuring Devices: HYGROMETER or PSYCHROMETER

 Specific Humidity = ACTUAL amount of moisture in the air. (Grams H 2 O / kg air)  Relative Humidity = percent mass of water vapor compared to mass water vapor at saturation. Ex: At 20 0 C, air contains 14.3g H 2 O / m 3 air. Saturation point: 17.1 g/m 3  Specific Humidity: 14.3 g/m 3  Relative Humidity: 14.3 g/m 3 = 84% Relative Humidity 17.1 g/m 3

 Dew Point = TEMPERATURE to which the air must be cooled to reach saturation.  Depends on Relative Humidity.  When temp. is below Dew Point: CONDENSATION (dew) or DEPOSITION (frost) occur

 Temperature Changes occur in 3 ways:  CONDUCTION: Transfer of heat through matter by molecular activity.  CONVECTION: transfer of heat by mass movement or circulation within a substance.  RADIATION: transfer of heat through matter or a vacuum by electromagnetic waves.

Section 18.2

Cloud Formation = from CONDENSATION of water vapor over a large area of air.

Land/Sea Breezes  Why does Winnipeg’s temperature vary so much more than Vancouver’s?  Vancouver is near the large ocean, which heats/cools slower than land. It holds that heat easily, keeping Vancouver’s air from fluctuating significantly.

 How do clouds affect Earth’s temperature during the day? Why?  Clouds reflect light away from the ground, keeping the temperature lower.  How do clouds affect Earth’s temperature during the night? Why?  Clouds insulate the air, keeping heat from escaping, keeping the temperature higher.

Types of Precipitation  ***The type of precipitation that reaches Earth’s surface is determined by the temperatures in the lowest few kilometers of the atmosphere.  Rain & Snow  Sleet = small particles of clear-to-translucent ice.

 Glaze = A.K.A. “FREEZING RAIN” – rain is supercooled (below 0°C) & become ice when they impact frozen objects.  Hail = small ice pellets grow as they impact supercooled water droplets as they fall through a cloud. UPDRAFTS push them back up, so they can gain new ice layers.

PRESSURE CENTERS & WIND ~section 19.2~  - Most common features on any weather map & weather generalizations can be made using them  - Winds are influenced by pressure (pressure gradients) centers and the Coriolis effect

 What goes in, must come out!!!!  When there is a converging air mass at the surface, it must be balanced by outflow  - a surface CONVERGENCE can be maintained if a DIVERGENCE occurs above the low at the same rate as the inflow below and vice versa. Air spreads out (diverges) above surface cyclones and comes together (converges) above surface anticyclones

Weather Maps  ISOBARS = lines that connect points of equal air pressure  Closely spaced lines indicate 2 things:  Strong pressure gradient  High winds  ISOTHERM = lines that connect points of equal temperature