| A | B |
|---|
| atmosphere | the layer of gases that surrounds Earth |
| air pressure | the pressure caused by the weight of a column of air in Earth's atmosphere |
| barometer | an instrument used to measure air pressure |
| troposhere | the lowest layer of Earth's atmosphere, where most weather occurs |
| weather | the condition of the atmosphere at a particular place at a particular time |
| stratosphere | the layer of Earth's atmosphere above the troposphere |
| ozone layer | a region of ozone concentration in the stratosphere |
| mesosphere | the layer of Earth's atmosphere immediately above the stratosphere |
| thermosphere | the outermost layer of Earth's atmosphere |
| ionosphere | a region of charged particles, or ions, in Earth's atmosphere that overlaps the lower thermosphere |
| aurora | a colorful display of light in the ionosphere, producedwhen charged particles from the suna re attracted to Earth's magnetic poles |
| rotation | the spining of a planet or moon on its axis |
| revolution | the movement of one body around another |
| tropic zone | a warm region between latitude 23.5 degrees south and latitde 23.5 degrees north |
| temperate zones | the regions between latitude 23.5 north and latitiude 66.5 north, and between latitude 23.5 south and latitude 66.5 south, which are generally cooler that the tropics |
| polar zones | the regions from latitude 66.5 north to the north pole, and from latitude 66.5 south to the south pole, which are generally cold |
| solstice | the day that marks the start of summer or winter, the day when the sun is directly overhead at latitude 23.5 north or latitude 23.5 south |
| equinox | a day that marks the beginning of spring, or autumn, a day on which the length of daylight and darkness are apporximately equal |
| greenhouse effect | a process in which Earth's atmosphere, such as water vapor and carbon dioxide, allow visible light to pass through but absorb reradiated infrared radiation that warms the lower atmosphere |
| wind | the mainly horizontal movement of air from areas of higher pressure to areas of lower pressure |
| local wind | a wind that blows over a short distance |
| sea breeze | a local wind that occurs when cooler air over the water flows toward the land |
| land breeze | a local wind that occurs when cooler air over land moves toward water |
| global wind | a wind that blows over long distances from a specific direction |
| Coriolis effect | the change that Earth's rotation causes in the motion of objects |
| monsoon | a wind system that shows a seasonal reversal of direction |
| jet stream | a belt of high-speed wind in the upper troposphere |
| humidity | the amount of water vapor in a given volume of air |
| relative humidity | the ratio of the amount of water vapor in the air to the maximum amount of water vapor that air can contain at that temperature |
| dew point | the temperature at which air becomes saturated with water vapor |
| cloud | a dense, visible mass of tiny water droplets or ice crystals that are suspended in the atmosphere |
| fog | a cloud that is touching or is near to the ground |
| stratus clouds | flat layers of clouds that cover much or all of the sky |
| cumulus clouds | puffy white clouds, usually with flat bottoms, that look like piles of cottong balls |
| cirrus clouds | thin, white, wispy clouds, often with a feathery or veil-like appearance |
| air mass | a large body of air that has consistent properties throughout, such as temperature and moisture content, at a given altitude |
| front | a sharply defined boundary that forms when two unlike air masses meet |
| cold front | a front that occurs when a cold air mass overtakes a warm air mass |
| warm front | a front that occurs when a warm air mass overtakes a cold air mass |
| stationary front | a front that occurs when two air masses have formed a boundary but neither is moving |
| occluded front | a front that occurs when a warm air mass is caught between two cooler air masses |
| cyclone | a weather system with a center of low air pressure |
| anticyclone | a weather system with a swirling center of high air pressure |
| thunderstorm | a small weather system that includes thunder and lightning |
| lightning | a sudden naturally occurring electrical discharge in the atmosphere |
| thunder | the sound produced by rapidly expanding air along the path of a lightning discharge |
| tornado | a small but intense windstorm that takes the form of a rotating column of air that touches the ground |
| hurricane | a large tropical cyclone with winds of at least 119 kilometers per hour (74 miles per hour) |
| meteoroligists | scientists who study and try to predict weather |
| isotherm | a line on a weather map that connects points of equal air temperature |
| isobar | a line on a weather map that connects points of equal air pressure |
| climate | the long-term weather conditions of a place or region |
| desert | an extremely dry region |
| ice ages | periods when climates are colder that usual and glaciers cover a large portion of Earth's surface |
| El Nino | the periodic warming of water in the central and eastern Pacific Ocean |
| global warming | an increase in the temperature of Earth's lower atmosphere, caused in part by increased levels of carbon dioxide or water vapor |
