1
Focus Question 11.1 Distinguish between weather and climate. 2
Focus on the Atmosphere Weather Occurs over a short period of time Constantly changing Climate Averaged over a long period of time Generalized, composite of weather 3
Focus on the Atmosphere Elements of weather and climate Properties that are measured regularly: Temperature Humidity Cloudiness Precipitation Air pressure Wind speed and direction
Focus on the Atmosphere
Focus Question 11.1 Distinguish between weather and climate. Weather Occurs over a short period of time Constantly changing Climate Averaged over a long period of time Composite of weather 6
Focus Question 11.2 What is ozone? Why is ozone important to life on Earth? 7
Composition of the Atmosphere Air is a mixture of discrete gases Major components of clean, dry air 78% Nitrogen (N) 21% Oxygen (O2) Argon and other gases 0.036% Carbon dioxide (CO2)
Composition of the Atmosphere
Composition of the Atmosphere Variable components of air Water vapor Up to 4% of air’s volume Forms clouds and precipitation Greenhouse gas Aerosols Tiny solid and liquid particles Water vapor can condense on solids Reflect sunlight Color sunrise and sunset
Composition of the Atmosphere
Composition of the Atmosphere Variable components of air Ozone Three atoms of oxygen (O3) Distribution not uniform Concentrated between 10 and 50 km above the surface Absorbs harmful UV radiation Human activity is depleting ozone by adding Chlorofluorocarbons (CFCs)
Composition of the Atmosphere
Focus Question 11.2 What is ozone? Why is ozone important to life on Earth? Three atoms of oxygen (O3) Absorbs harmful UV radiation that negatively impacts life on Earth 14
Focus Question 11.3 What is the environmental lapse rate, and how is it determined? 15
Vertical Structure of the Atmosphere Atmospheric pressure is the weight of the air above. Average sea level pressure is 1000 millibars or 14.7 psi Pressure decreases with altitude Half of atmosphere is below 3.5 mi (5.6 km) 90% of atmosphere is below 10 mi (16 km)
Vertical Structure of the Atmosphere
Vertical Structure of the Atmosphere Atmospheric layers based on temperature Troposphere Bottom layer Temperature decreases with altitude Environmental lapse rate Average 6.5˚C per km or 3.5˚F per 1000 feet Thickness varies Average height is about 12 km Outer boundary is the tropopause
Vertical Structure of the Atmosphere
Vertical Structure of the Atmosphere The environmental lapse rate is variable Actual environmental lapse rate for any particular time and place Measured with a radiosonde Attached to a balloon and transmits data by radio
Vertical Structure of the Atmosphere
Vertical Structure of the Atmosphere Stratosphere 12 to 50 km Temperature increases at top Outer boundary is the stratopause Mesosphere 50 to 80 km Temperature decreases Outer boundary is the mesopause Thermosphere No well-defined upper limit Fraction of atmosphere’s mass Gases moving at high speeds
Vertical Structure of the Atmosphere
Focus Question 11.3 What is the environmental lapse rate, and how is it determined? The environmental lapse rate is the temperature decrease in the troposphere It is determined by measurement with a radiosonde 24
Focus Question 11.4 Briefly explain the primary cause of the seasons. 25
Earth–Sun Relationships Earth motions Rotates on its axis Revolves around the Sun Seasons Result of: Changing Sun angle Changing length of daylight
Earth–Sun Relationships
Earth–Sun Relationships Seasons Caused by Earth’s changing orientation to the Sun Axis is inclined 23.5º Axis is always pointed in the same direction
Earth–Sun Relationships Special days (Northern Hemisphere) Summer solstice: June 21–22 Sun’s vertical rays located at Tropic of Cancer 23.5º N latitude Winter solstice: December 21–22 Sun’s vertical rays located at Tropic of Capricorn 23.5º S latitude Autumnal equinox: September 22–23 Sun’s vertical rays located at equator (0º latitude) Spring equinox: March 21–22
Earth–Sun Relationships
Focus Question 11.4 Briefly explain the primary cause of the seasons. Earth’s changing orientation to the Sun Changing Sun angle Changing length of daylight 31
Focus Question 11.5 Distinguish between heat and temperature. 32
Energy, Heat, and Temperature Heat is synonymous with thermal energy Temperature refers to the intensity, or degree of "hotness" Heat is always transferred from warmer to cooler objects Mechanisms of heat transfer Conduction Molecular activity Convection Mass movement within a substance Radiation (electromagnetic radiation) Gamma waves, X-rays Ultraviolet,visible, infrared Microwaves and radio waves
Energy, Heat, and Temperature
Energy, Heat, and Temperature Laws of Radiation All objects emit radiant energy Hotter objects radiate more total energy per unit area than colder objects Hotter objects radiate more short-wavelength radiation than cooler objects Good absorbers of radiation are good emitters as well
Energy, Heat, and Temperature
Focus Question 11.5 Distinguish between heat and temperature. Heat refers to the quantity of energy present Temperature is the degree of “hotness” 37
Focus Question 11.6 What factors cause albedo to vary from time to time and from place to place? 38
Heating the Atmosphere Incoming solar radiation Atmosphere is largely transparent to incoming solar radiation Atmospheric effects Reflection Albedo (percent reflected) Scattering Absorption Most visible radiation reaches the surface About 50% absorbed at Earth’s surface
Heating the Atmosphere
Heating the Atmosphere
Heating the Atmosphere
Heating the Atmosphere Radiation from Earth’s surface Earth re-radiates longer wavelengths Terrestrial radiation Terrestrial radiation is absorbed by Carbon dioxide and water vapor Lower atmosphere is heated from Earth’s surface Heating of the atmosphere is termed the greenhouse effect
Heating the Atmosphere
Focus Question 11.6 What factors cause albedo to vary from time to time and from place to place? Amount of cloud cover and particulate matter Angle of the Sun’s rays Nature of Earth’s surface 45
Focus Question 11.7 Why has the CO2 level of the atmosphere been increasing for the past 200 years? 46
Human Impact on Global Climate CO2 levels are rising Industrialization of the past 200 years Burning fossil fuels coal, natural gas, and petroleum Deforestation Present CO2 level is 30% higher than its highest level over the past 650,000 years
Human Impact on Global Climate
Human Impact on Global Climate
Human Impact on Global Climate
Focus Question 11.7 Why has the CO2 level of the atmosphere been increasing for the past 200 years? Industrialization Burning fossil fuels coal, natural gas, and petroleum Deforestation 51
Human Impact? How might the current climate change situation be different if humans had developed the steam engine instead of the gasoline engine? 52
For the Record: Air Temperature Data Temperature measurement Daily maximum and minimum Other measurements Daily mean temperature Daily range Monthly mean Annual mean Annual temperature range
For the Record: Air Temperature Data Isotherms used to examine distribution of air temperatures over large areas Line that connects points of the same temperature iso = equal, therm = temperature
For the Record: Air Temperature Data
Focus Question 11.9 How can cloud cover influence the maximum temperature on an overcast day? 56
Why Temperatures Vary: The Controls of Temperature Receipt of solar radiation Other important controls Differential heating of land and water Land heats more rapidly than water Land gets hotter than water Land cools faster than water Land gets cooler than water
Why Temperatures Vary: The Controls of Temperature
Why Temperatures Vary: The Controls of Temperature Other important controls Altitude Geographic position Cloud cover Albedo
Why Temperatures Vary: The Controls of Temperature
Focus Question 11.9 How can cloud cover influence the maximum temperature on an overcast day? Clouds reflect a significant portion of sunlight Reducing amount of incoming solar radiation Daytime temperatures will be lower 61
World Distribution of Temperature Temperature maps Temperatures are adjusted to sea level January and July used for analysis Represent temperature extremes
World Distribution of Temperature Global temperature patterns Temperature decreases poleward from tropics Isotherms exhibit latitudinal shift with seasons Warmest and coldest over land
World Distribution of Temperature
World Distribution of Temperature Global temperature patterns Southern Hemisphere Isotherms are straighter Isotherms are more stable Isotherms show ocean currents Annual temperature range Small near equator Increases with an increase in latitude Greatest over continental locations