That evaporation, the thinking goes, absorbs energy and keeps the countryside cooler. Local climate may matter more. Zhao and colleagues began with a question: Would similar cities located in different climates experience the same increase in temperature from the urban heat island effect?
At mid-day, though, wetter cities experienced a greater heat island effect. The researchers then created a computer model that let them evaluate the importance of various factors that might influence the urban heat island effect.
These included features such as evaporation, heat created by humans and their structures and heat stored by cities.
Also included were differences in the land and in convection—the transfer of heat from the city or rural region to the atmosphere. The air in the mesosphere has extremely low density: As a result, air pressure is very low Figure below. A person traveling through the mesosphere would experience severe burns from ultraviolet light since the ozone layer which provides UV protection is in the stratosphere below.
There would be almost no oxygen for breathing. Meteors burn in the mesosphere even though the gas is very thin; these burning meteors are shooting stars. The density of molecules is so low in the thermosphere that one gas molecule can go about 1 km before it collides with another molecule. Since so little energy is transferred, the air feels very cold Figure above. Within the thermosphere is the ionosphere. The ionosphere gets its name from the solar radiation that ionizes gas molecules to create a positively charged ion and one or more negatively charged electrons.
The freed electrons travel within the ionosphere as electric currents. Because of the free ions, the ionosphere has many interesting characteristics. At night, radio waves bounce off the ionosphere and back to Earth.
This is why you can often pick up an AM radio station far from its source at night. The Van Allen radiation belts are two doughnut-shaped zones of highly charged particles that are located beyond the atmosphere in the magnetosphere.
The particles originate in solar flares and fly to Earth on the solar wind. These lines extend from above the equator to the North Pole and also to the South Pole then return to the equator. When massive solar storms cause the Van Allen belts to become overloaded with particles, the result is the most spectacular feature of the ionosphere — the nighttime aurora Figure below.
The particles spiral along magnetic field lines toward the poles. The charged particles energize oxygen and nitrogen gas molecules, causing them to light up. Each gas emits a particular color of light. There is no real outer limit to the exosphere , the outermost layer of the atmosphere; the gas molecules finally become so scarce that at some point there are no more.
Most Earth satellites orbit in the exosphere. The Edge of Outer Space. Called INCUS, it aims to directly address why convective storms, heavy precipitation, and clouds occur exactly when and where they form. Climate change is contributing to hot and dry conditions in the American West, ideal for the spread of fires.
An experimental tool can help communities track potential air quality impacts from wildfire smoke. The three types are:. The remaining solar radiation is the longest wavelength, infrared.
Most objects radiate infrared energy, which we feel as heat. Some of the wavelengths of solar radiation traveling through the atmosphere may be lost because they are absorbed by various gases.
Oxygen, carbon dioxide, and water vapor also filter out some wavelengths. Heat moves in the atmosphere the same way it moves through the solid Earth Plate Tectonics chapter or another medium. What follows is a review of the way heat flows and is transferred, but applied to the atmosphere. Radiation is the transfer of energy between two objects by electromagnetic waves.
Heat radiates from the ground into the lower atmosphere. In conduction , heat moves from areas of more heat to areas of less heat by direct contact. Warmer molecules vibrate rapidly and collide with other nearby molecules, transferring their energy. In the atmosphere, conduction is more effective at lower altitudes where air density is higher; transfers heat upward to where the molecules are spread further apart or transfers heat laterally from a warmer to a cooler spot, where the molecules are moving less vigorously.
Heat transfer by movement of heated materials is called convection. Heat that radiates from the ground initiates convection cells in the atmosphere. This energy can be absorbed by atmospheric gases, reflected by clouds, or scattered.
Scattering occurs when a light wave strikes a particle and bounces off in some other direction. The rest is absorbed by rocks, soil, and water and then radiated back into the air as heat. These infrared wavelengths can only be seen by infrared sensors. The answer is no although the next section contains an exception because energy from Earth escapes into space through the top of the atmosphere. If the amount that exits is equal to the amount that comes in, then average global temperature stays the same.
What happens if more energy comes in than goes out? If more energy goes out than comes in? The amount of incoming solar energy is different at different latitudes. Where do you think the most solar energy ends up and why?
Where does the least solar energy end up and why? The difference in solar energy received at different latitudes drives atmospheric circulation. Different greenhouse gases have different abilities to trap heat. For example, one methane molecule traps 30 times as much heat as one CO 2 molecule. Still, CO 2 is a very important greenhouse gas because it is much more abundant in the atmosphere. Human activity has significantly raised the levels of many of greenhouse gases in the atmosphere.
CFCs have only recently existed. What do you think happens as atmospheric greenhouse gas levels increase? More greenhouse gases trap more heat and warm the atmosphere. The increase or decrease of greenhouse gases in the atmosphere affect climate and weather the world over. Skip to main content. The Atmosphere. Search for:. All weather takes place in the atmosphere, virtually all of it in the lower atmosphere.
Weather describes what the atmosphere is like at a specific time and place, and may include temperature, wind, and precipitation. Weather is the change we experience from day to day.
Climate is the long-term average of weather in a particular spot. Although the weather for a particular winter day in Tucson, Arizona, may include snow, the climate of Tucson is generally warm and dry.
Ozone in the upper atmosphere absorbs high-energy ultraviolet UV radiation coming from the Sun. Without ozone for protection, only the simplest life forms would be able to live on Earth.
Greenhouse gases trap heat in the atmosphere so they help to moderate global temperatures. Important greenhouse gases include carbon dioxide, methane, water vapor, and ozone. The rest of the gases are minor components but sometimes are very important. Humidity is the amount of water vapor in the air. Humidity varies from place to place and season to season. This fact is obvious if you compare a summer day in Atlanta, Georgia, where humidity is high, with a winter day in Phoenix, Arizona, where humidity is low.
When the air is very humid, it feels heavy or sticky. Dry air usually feels more comfortable. Where around the globe is mean atmospheric water vapor higher and where is it lower and why? Higher humidity is found around the equatorial regions because air temperatures are higher and warm air can hold more moisture than cooler air.
Of course, humidity is lower near the polar regions because air temperature is lower. The air density the number of molecules in a given volume decreases with increasing altitude.
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