•Vital functions of the atmosphere include the following:
◦keeps Earth's temperature steady and habitable
◦protects from ultraviolet radiation
◦protects from meteorite impacts
◦provides oxygen for respiration and carbon dioxide for photosynthesis
•The atmosphere consists primarily of nitrogen (78%) and oxygen (21%) gases. Together they make up 99% of the atmosphere.
•Trace gases make up the remaining 1% of the atmosphere. Trace gases include argon, neon, and hydrogen.
•Variable gases, as their name suggests, vary in concentration. Important variable gases are carbon dioxide, water vapor, and ozone.
•The layers of the atmosphere have distinguishing features. Here's a summary:
◦Troposphere—This is the layer we most interact with, whether we are breathing or hang gliding. Temperature decreases with altitude. Almost all weather occurs here.
◦Stratosphere—This layer has steady winds, good for long-distance flights. Temperature increases with altitude due to the ozonosphere in the upper part of the layer.
◦Mesosphere—This layer burns up meteors, seen as falling or shooting stars. Temperature decreases with altitude. It is the coldest layer of the atmosphere.
◦Thermosphere—In this layer, gases are layered, not mixed. It consists of two sub-layers: ionosphere—where auroras occur and radio waves are reflected—and exosphere—where satellites hover. It is the hottest layer of the atmosphere, until it blends into space.
•The atmosphere is dynamic. It transports and recycles materials.
•The atmosphere is a superhighway. It can transport matter across the country in days. It helps to transport, distribute, and recycle materials.
•The water cycle describes the evaporation, condensation, and precipitation of water. This process distributes heat and energy, maintaining a warm global atmosphere.
•The nitrogen cycle provides nitrates for living organisms, which use nitrates for nucleic and amino acids. The atmosphere provides the nitrogen for this cycle.
•Carbon and oxygen are also essential for living organisms. The carbon-oxygen cycle moves carbon dioxide and oxygen from the atmosphere or hydrosphere, distributing it to plants and other living organisms for cellular growth. These gases also assist with blocking ultraviolet radiation and maintaining a warm temperature on Earth.
•The earth's energy budget refers to the balance of energy coming in and the amount going out. The stability of temperature on Earth depends on the earth's energy budget.
•Earth's energy budget, greenhouse gases, and the water cycle affect atmospheric temperatures.
•Radiation, conduction, and convection are processes that transfer heat.
•Atmospheric moisture or humidity depends on water sources and temperature. Hot and moist regions tend to experience more thunderstorm activity due to greater latent heat in water vapor.
•Earth's gravitational force pulls air molecules toward its surface. So, air has weight. This weight is air pressure.
•Lower layers of the atmosphere are denser and have more air pressure than upper layers. Air pressure decreases with altitude.
•A common tool that measures air pressure is a barometer. Most meteorologists can predict weather by studying pressure changes. High pressure usually means good weather, and low pressure usually means bad weather.
•The wind blows because of uneven heat distribution. Convection currents or cells transfer heat by moving air. Wind moves from high-pressure (cold air is denser) to low-pressure (warm air is lighter) areas.
•Circular patterns of ocean and wind currents are created due to the Earth's rotation. This is known as the Coriolis effect.
•Wind currents can also change due to static features, like mountains or buildings. Areas near large bodies of water have a land breeze (land to sea) at night and sea breeze (sea to land) during the day.
•The greenhouse effect refers to the atmospheric blanket of gases that act like the glass of a greenhouse—allowing heat to enter Earth's atmosphere and trapping some of it.
•Air pollution is waste material not normally found in the air. Two main pollutants are particles and gases.
•Pollutants are produced by human activities, such as burning fossil fuels for driving, heating homes, or running businesses.
•Air pollution contributes to global warming, which can affect climate change. Plate tectonics and Milankovitch cycles are natural processes that also affect climate.
•Air pollution can have ill effects on health, causing respiratory and heart distress. It can destroy plant, animal, and aquatic ecosystems.
•Sulfur oxides and nitrogen oxides produce acid rain, which harms plants and aquatic ecosystems and damages buildings and other structures.
•CFCs have created a hole in the ozone layer, the layer that blocks some of the Sun's UV rays. This has increased skin cancer and harmed plants and animals.
•Congress and state legislatures have passed many laws to reduce air pollution, like vehicle emissions requirements, higher fuel efficiency, mass transit, and lower power plant emissions.