6th Grade
Weather
Key Terms

Acid Rain- Rain that contains more acid than normal 

Air Mass  A huge body of air that has similar temperature, pressure, and humidity throughout. Air Pressure- A force that is the result of the weight of a column of air pushing down on an area. 

Altitude- Elevation above sea level. 

Anemometer- An instrument used to measure wind speed. 

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.   

Anticylone- A high-pressure center of dry air. 

Atmosphere- The layer of gases that surrounds Earth. 

Aurora borealis- A colorful, glowing display in the sky caused when particles from the sun strike oxygen and nitrogen atoms in the ionosphere; also called the Northern Light. 

Barometer- An instrument used to measure changes in air pressure. 

Chlorofluorocarbons- Chlorine compounds formerly used in air conditioners, refrigerators, and spray cans; also called CFCs.   

Cirrus- Wispy, feathery clouds made mostly of ice crystals that form at high levels, above about 6 kilometers. 

Climate- The average, year-after-year conditions of temperature, precipitation, winds, and clouds in an area. 

Condensation- The process by witch molecules of water vapor in the air became liquid water. Conduction- The direct transfer of heat from one substance to another substance that it is touching. 

Continental (air mass)- A dry air mass that forms over land. 

Continental climate- The climate of the centers of continents, with cold winter and warm or hot summers. 

Controlled experiment- An experiment in which all factors except one ore kept constant.Convection- The transfer heat by the movement of a fluid. 

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. 

Cumulus- Clouds that form less than 2 kilometers above the ground and look like fluffy, rounded piles of cotton. 

Cyclone-  A swirling center of low air pressure. 

Density-  The amount of mass of a substance to a given volume. 

Desert- A region that gets less than 25 centimeters of rain a year. 

Dew point- The temperature at witch condensation begins. 

Drought- Long period of low precipitation.  

El Nino- An event that occurs every two to seven years in the Pacific Ocean, during which winds shift and push warm surface water toward the coast of South America; it can cause dramatic climate changes. 

Electromagnetic wave- A form of energy that can travel through space. 

Evacuate- To move away temporarily. 

Evaporation- The process by which water molecules in liquid water escape into the air as water vapor. 

Exosphere- The outer layer of the thermosphere, extending outward into space. 

Flash flood- A sudden, violent flood that occurs within a few hours, or even minutes , of a heavy rainstorm. Front- The area where air masses meet and do not mix. 

Global warming- A gradual increase in the temperature of Earth’s atmosphere. 

Global winds- Winds that blow steadily from specific directions over long distance

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. 

Green house gases- Gases in the atmosphere that trap heat.

 Heat- The energy transferred from a hotter object to a cooler one. 

Humid subtropical- A wet and warm climate area on the edge of the tropics. 

Humidity- A measure of the amount of water vapor in the air. 

Hurricane- A tropical storm that has winds of 119 kilometers per hour or higher; typically about 600 kilometers across. 

Hypothesis- A prediction about the out come of an experiment. 

Ice ages- cold time periods in earth’s history, during which glaciers covered large parts of the surface. 

Infrared radiation- A form of energy with wavelengths that are longer than visible light. 

Ionosphere- The lower part of the thermosphere, where electrically charged particles called ions are found. 

Isobars Lines- on a map joining places that have the same air pressure. 

Isotherms – Lines on a map joining places that have the same temperature. 

Jet Stream – bands of high-speed winds about 10 kilometers above Earth’s surface.

 Land breeze- The flow of air from land to a body of water. 

Latitude- The distance from the equator, measured in degrees. 

Leeward- The downwind side of mountains. 

Lightening- A sudden spark, or energy discharge, caused when electrical charges jump between parts of cloud or between a cloud and the ground. 

Local winds- Winds that blow over short distances. 

Manipulated variable- The one factor that a scientist changes during an experiment. 

Marine climate- The climate of some coastal regions, with relatively warm winter and cool summers. 

Maritime (air mass)  A humid air mass that forms over oceans. 

Mercury barometer- an instrument that measures changes in air pressure, consisting of a glass tube partially filled with mercury.  Air pressure pushing on the mercury in the dish forces the mercury in the tube higher.   

Mesosphere- The middle layer of Earth’s atmosphere: the layer in which most meteoroids burn up. Meteorologists- Scientists who study the causes of weather and try to predict it. 

Microclimate- The climate characteristic of a small, specific area; it may be different from the climate of the surrounding area. 

Monsoons- Sea and land breezes over a large region that change direction with the seasons. 

Occluded- Cut off, as the warm air mass at an __ front is cut off from the ground by cooler air beneath it. 

Operational definition.-A statement that describes how a particular variable is to be measured or a term is to be defined. 

Ozone- A form of oxygen that has three oxygen atoms in each molecule instead of the usual to. 

Permafrost-  Permanently frozen soil found in the tundra climate region. 

Photochemical smog- A brownish haze that is a mixture of ozone and other chemicals, formed when nitrogen oxides, hydrocarbons, and other pollutants react with each other in the presence of sunlight. 

Polar (air mass)- A cold air mass that forms north of 50 degrees north latitude or south of 50 degrees south latitude and has high air pressure. 

Polar Zones- The areas near both poles, from about 66.5 to 90 north and 66.5 to 90 south latitudes 

Pollutants- Harmful substances in the air, water or soil. 

Precipitation- Any form of water that falls from clouds and reaches Earth’s surface. 

Pressure- The force pushing on an area or surface. 

Psychrometer- An instrument used to measure relative humidity, consisting of a wet-bulb thermometer and a dry-bulb thermometer.

 Radiation- The direct transfer of energy by electromagnetic waves. 

Rain forest- A forest in the tropical wet climate zone that gets plenty of rain all year. 

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. 

Relative humidity- the percentage of water vapor in the air compared to the maximum amount the air could hold at that temperature. 

Responding variable- The factor that changes as a result of changes to the manipulated variable in an experiment. 

Savanna- A tropical grassland with scattered clumps of trees;  found in the tropical wet-and dry climate zone. Scattering- Reflection of light in all directions.

 Sea breeze- The flow of air from an ocean or lake to the land. 

Steppe-  A prairie or grassland found in the semiarid climate region. 

Storm- A violent disturbance in the atmosphere. 

Storm Surge- A dome of water that sweeps across the coast where a hurricane lands. 

Stratosphere- The second-lowest layer of Earth’s atmosphere; the ozone layer is located in the upper stratosphere. 

Stratus- Clouds that form in flat layers. 

Subarctic- A climate zone that lies north of the humid continental climate zone, with short, cool summers and long, bitter cold winters. 

Sunspots- Dark, cooler regions on the surface of the sun.  

Temperate zones- The area between the tropical and polar zones, from about 23.5 to 66.5 north and 23.5 to 66.5 south latitudes. 

Temperature- the average amount of energy of motion in the molecules of a substance. 

Thermal energy-   The energy of motion in the molecules of a substance. 

Thermometer-   An instrument used to measure temperature, consisting of a thin, glass tube with a bulb on one end that contains a liquid  ( usually mercury or alcohol). 

Thermosphere- The outermost layer of Earth’s atmosphere. 

Tornado- A rapidly whirling, funnel –shaped cloud that reaches down from a storm cloud to touch Earth’s surface, usually leaving a destructive path. 

Tropical (air mass)-  A warm air mass that forms in the tropics and has low air pressure.

 Tropical zone- The area near the equator, between about 23.5 north latitude and 23.5 south latitude.

Troposphere- The lowest layer of Earth’s atmosphere, where weather occurs.   

Tundra- A polar climate region, found across northern Alaska, Canada, and Russia, with short cool summers and bitterly cold winter.

 Ultraviolet radiation- A form of energy with wavelengths that are shorter than visible light. 

Variable- Any factor that can change in an experiment. 

Water vapor- Water in the form of a gas 

Weather- The condition of Earth’s atmosphere at a particular time and place. 

Wind- The horizontal movement of air from an area of high pressure to an area of lower pressure.

 Wind- chill factor- Increased cooling caused by the wind. 

Windward- the side of mountains that faces the ocean