Word | Definition |
weather | The condition of Earth's atmosphere at a particular time and place. |
atmosphere | The layer of gases that surrounds Earth. |
ozone | A form of oxygen that has three oxygen atoms in each molecule instead of the usual two. |
water vapor | Water in the form of gas. |
pollutants | Harmful substances in the air, water, or soil. |
density | The amount of mass of a substance to a given volume. |
pressure | The force pushing on an area or surface. |
air pressure | A force that is the result of the weight of a column of air pushing down on an area. |
barometer | An instrument used to measure changes in air pressure. |
mercury barometer | An instrument that measures changes in air pressure, consisting of a glass tube partially filled with mercury, with its open end resting in a dish of mercury. Air pressure pushing on the mercury in the dish forces the mercury in the tube to be higher. |
aneroid barometer | An instrument that measures changes in air pressure without using a liquid. Changes in the shape of an airtight metal box cause a needle on the barometer dial to move. |
condensation | The process by which molecules of water vapor in the air become liquid water. |
dew point | The temperature at which condensation begins. |
altitude | Elevation above sea level. |
troposphere | The lowest layer of Earth's atmosphere, where weather occurs. |
stratosphere | The second-lowest layer of Earth's atmosphere; the ozone layer is located in the upper stratosphere. |
mesosphere | The middle layer of Earth's atmosphere; the layer in which most meteoroids burn up. |
thermosphere | The outermost layer of Earth's atmosphere. |
electromagnetic wave | A form of energy that can travel through space. |
radiation | The direct transfer of energy by electromagnetic waves. |
greenhouse effect | The process by which heat is trapped in the atmosphere by water vapor, carbon dioxide, methane, and other gases that form a "blanket" around Earth. |
thermal energy | The energy of motion in the molecules of a substance. |
heat | The energy transferred from a hotter object to a cooler one. |
conduction | The direct transfer of heat from one substance to another substance that it is touching. |
precipitation | Any form of water that falls from cluds and reaches Earth's surface. |
rain gauge | An instrument used to measure the amount of precipitation, consisting of an open-ended can topped by a collecting funnel and having a collecting tube and measuring scale inside. |
droughts | Long periods of low precipitation. |
convection | The transfer of heat by the movement of a fluid. |
wind | The horizontal movement of air from an area of high pressure to an area of lower pressure. |
anemometer | An instrument used to measure wind speed. |
wind-chill factor | Increased cooling caused by the wind. |
local winds | Winds that blow over short distances. |
global winds | Winds that blow steadily from specific directions over long distances. |
Coriolis effect | The way Earth's rotation makes winds in the Northern Hemisphere curve to the right and winds in the Southern Hemisphere curve to the left. |
latitude | The distance from the equator, measured in degrees. |
jet streams | Bands of high-speed winds about 10 kilometers above Earth's surface. |
evaporation | The process by which water molecules in liquid water escape into the air as water vapor. |
humidity | A measure of the amount of water vapor in the air. |
relative humidity | The percentage of water vapor in the air compared to the maximum amount the air could hold at that temperature. |
psychrometer | An instrument used to measure relative humidity, consisting of a wet-bulb thermometer and a dry-bulb thermometer. |
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