Monday, 8/31/091 ATMO Class #2 Monday, August 31, 2009 Chapter 1 Introduction to the Atmosphere

Definitions Meteorology is the study of weather variables—temperature, humidity, pressure, wind speed and direction, cloud cover, precipitation Climate is the condition of the atmosphere over many years, including averages, seasonal changes and records of extremes Monday, 8/31/092

Meteorology and Atmospheric Science Usually used interchangeably Atmospheric science includes not only meteorology but some other topics as well –Charged particles and electricity in the ionosphere, parts of the upper atmosphere –Atmospheres of other planets –Includes the study and simulation of climate –Includes the study of climate change Monday, 8/31/093

4 What’s in the atmosphere? Invisible gases –Some permanent, some variable –Some abundant, some not (trace gases) –Some greenhouse, some not –Some pollutants, some not Liquids –Water: cloud droplets, raindrops, haze, fog –Pollutants Solids –Water: ice crystals in clouds, snow –Soil, sand, acid, pollen, other substances

Monday, 8/31/095 Abundance of gases in the atmosphere

Monday, 8/31/096 Gases in the atmosphere Nitrogen: most abundant (78%), not very reactive, permanent, not a greenhouse gas, emitted from volcanoes Oxygen (O 2 : 2 nd most abundant (21%), essential for combustion, respiration, a greenhouse gas only in the stratosphere and above (not near the surface), permanent, comes from plants as a product of photosynthesis

Monday, 8/31/097 Other gases in the atmosphere Argon (1%), permanent, not reactive Water vapor, highly variable (0-4%), extremely important to the weather and essential to life, most abundant of the greenhouse gases, comes from volcanoes and maybe comets, hugely important to climate, invisible, makes air lighter –Part of a cycle called the hydrologic cycle –Has a whole chapter, Chapter 4

Monday, 8/31/098 The Hydrologic Cycle: sources and sinks

Monday, 8/31/099 Still another gas in the atmosphere Carbon dioxide, the 2 nd most abundant greenhouse gas, variable with concentrations increasing every year and higher now than ever before in Earth’s history, important for climate change and global warming –Has a cycle of sources and sinks called the Carbon Dioxide (CO 2 ) Cycle

Monday, 8/31/0910 Carbon dioxide measurements at Mauna Loa, Hawaii

Monday, 8/31/0911 The carbon dioxide cycle

Monday, 8/31/0912 Another gas: Methane –Is another important greenhouse gas –Concentrations are increasing –Comes from human activities, including the cultivation of rice, burning of forests, coal mining, and cattle raising (digestive processes of domestic animals) –Also comes from termites

Monday, 8/31/0913 Increasing concentrations of methane

Monday, 8/31/0914 Ozone (O 3 ) Is another important greenhouse gas Forms naturally in the stratosphere from oxygen, and warms the stratosphere Allowed life to develop over land Gets depleted over Antarctica in winter— known as the “ozone hole” Is a dangerous pollutant near Earth’s surface

Monday, 8/31/0915 Layers of the Atmosphere

Monday, 8/31/0916 Chlorofluorocarbons (CFCs) Are yet more greenhouse gases, and very powerful Do not occur naturally Are chemically stable near the surface Are broken down in the stratosphere –Loose chlorine atoms destroy stratospheric ozone Are decreasing in emissions rapidly Are decreasing in concentrations slowly

Monday, 8/31/0917 Global use of CFCs

Monday, 8/31/0918 Concentration of CFCs

Monday, 8/31/0919 Particles of liquid and solid in the atmosphere Are together known as aerosols [ai(e)rborne solutions] Varies in size with the type of substance Are measured in units of microns (1/1,000,000 of a meter or 1/1,000 of a mm) Most are invisible because they are so small Are more abundant over deserts Are less abundant over the oceans Are needed to form clouds Can influence climate Can be pollutants Are anthropogenic when caused by human activity

Monday, 8/31/0920 Particles in the atmosphere

Monday, 8/31/0921 Smoke from fires in Southern California viewed by satellite

Monday, 8/31/0922 Pressure and density in the atmosphere Pressure is force per unit area Pressure always decreases upward Pressure is related to the weight of air in a column above a particular location Density is mass per unit volume Density always decreases upward Density is related to pressure by the gas law: pressure = constant x density x temperature

Monday, 8/31/0923 How pressure and density decrease upward

Monday, 8/31/0924 Surface pressure corrected to sea level

Monday, 8/31/0925 Pressure in the different layers of the atmosphere