Chapter 13

1. About how thick is Earth’s atmosphere? Name one characteristic of the troposphere and one characteristic of the stratosphere.
The Earth's atmosphere is about 300 miles (480 km) thick, but most of the atmosphere (about 80%) is within 10 miles (16 km) of the surface of the Earth.
The troposphere is the layer of the atmosphere in which we live, temperature decreases with altitude.
Stratosphere is where the ozone layer is.

2. Where is the “ozone layer” located? How and why is stratospheric ozone beneficial for people, whereas tropospheric ozone is harmful?
The “ozone layer” located on the stratosphere.
Stratospheric ozone (sometimes referred to as "good ozone") plays a beneficial role by absorbing most of the biologically damaging ultraviolet sunlight (called UV-B), allowing only a small amount to reach the Earth's surface.
At the Earth's surface, ozone comes into direct contact with life-forms and displays its destructive side (hence, it is often called "bad ozone"). Because ozone reacts strongly with other molecules, high levels of ozone are toxic to living systems.

3. How does solar energy influence weather and climate? How do Hadley, Ferrel, and polar cells help to determine long-term climatic patterns and the location of biomes?
Weather is driven by the circulation of air by convection currents. Solar radiation heats up the Earth's surface and the heated air picks up moisture and rises. This rising air cools, the moisture condenses and forms clouds and precipitation. The cool, drying air starts to sink and compress. As it compresses and sinks it becomes dry, warm air that will be heated up again and the cycle continues.
These large scale convection currents distribute heat and material throughout the globe and determine the humid and arid climate patterns. For example, the warm air near the equator rises, expands and cools leading to moisture condensing. This explains the wet climate in the tropical regions. The air travels towards the poles and since its cooler sinks at the 30 degree latitude, north and south. Since this cool air lost moisture in the tropics, the 30 degrees latitude regions are arid. This first cell is the Hadley Cell, but this pattern of warm air rising and cool air sinking continues in both hemispheres forming the Ferrel and polar cells and creating the moist and dry climates.

4. Describe a thermal inversion. How do inversions contribute to severe smog episodes like the ones in London and in Donora, Pennsylvania?
Thermal inversion occurs when a layer of warm air settles over a layer of cooler air that lies near the ground. The warm air holds down the cool air and prevents pollutants from rising and scattering.

5. How does a primary pollutant differ from a secondary pollutant? Give an example of each.
Primary: Materials that when released pose health risks in their unmodified forms. Such as CO2, CO as these gaseous are directly emitted from burning of fossil fuel.
Secondary: Primary pollutants interact with one another, sunlight, or natural gases to produce new, harmful compounds. Like smog which is formed by combination of smog and fog. And pesticides, insecticide.

6. What has happened with concentrations of “criteria pollutants” in U.S. ambient air in recent decades? What has happened with our emissions of major pollutants? Name one health risk from toxic air