Jump to definitions starting with: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Advection
The transport of energy or matter from one place to another.
Altimeter
An instrument that indicates the altitude of an object above a fixed level. Pressure altimeters use an aneroid barometer with a scale graduated in altitude instead of pressure. (National Weather Service)
Anomaly
The deviation of a measurable unit (e.g., temperature or precipitation) over a period in a given region from the long-term average, often the thirty-year mean, for that region.
Antarctic Circumpolar Current
A cold current encircling the Antarctic, driven by westerly winds between 40° and 70° S. Because the flow of this current is not checked by the continents, it links the Atlantic, Indian, and Pacific Oceans. (JPL)
Anticyclone
An area of high atmospheric pressure around which the wind blows clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. It is usually associated with fair weather.
Array for Real-time Geostrophic Oceanography (Argo)
A global array of 3,000 free-drifting profiling floats to continuously monitor the temperature and salinity of the upper 2000 m of the ocean. The ARGO array is part of GCOS/GOOS, CLIVAR, and GODAE.
Atmosphere
The mixture of gases surrounding the Earth. The Earth's atmosphere consists of about 79.1% nitrogen (by volume), 20.9% oxygen, 0.036% carbon dioxide and trace amounts of other gases. The atmosphere can be divided into a number of layers according to its mixing or chemical characteristics, generally determined by its thermal properties (temperature). The layer nearest the Earth is the troposphere, which reaches up to an altitude of about 8 km (about 5 miles) in the polar regions and up to 17 km (nearly 11 miles) above the equator. The stratosphere, which reaches to an altitude of about 50 km (31 miles) lies atop the troposphere. The mesosphere, which extends up to 80-90 km, is atop the stratosphere, and finally, the thermosphere, or ionosphere, gradually diminishes and forms a fuzzy border with outer space. There is relatively little mixing of gases between layers.
Buoyancy
The tendency of a body to float or to rise when submerged in a fluid; the power of a fluid to exert an upward force on a body placed in it. (National Weather Service)
Buoys
Floating platforms that hold instruments for measuring conditions in the ocean and atmosphere such as currents, water temperature, wind, and atmospheric pressure. Often they relay information to satellites.
California Current
The cold ocean current flowing southward along the western coast of North America from the Gulf of Alaska to Baja California.
Centripetal Force
The force pulling an object moving in a circular path inward towards the center.
Circulation
The flow, or movement, of a fluid (e.g., water or air) in or through a given area or volume. (National Weather Service)
Climate
The average weather for a particular region and time period (usually taken over a 30-year time period). Climate is not the same as weather, but rather, it is the average of weather for a particular region. Weather describes the short-term state of the atmosphere. Climatic elements include precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, and hail storms, and other measures of the weather.
Climate Change
Sometimes used to refer to all forms of climatic inconsistency, but because the Earth's climate is never static, the term is more properly used to imply a significant change from one climatic condition to another. In some cases, 'climate change' has been used synonymously with the term, 'global warming'; scientists however, tend to use the term in the wider sense to also include natural changes in climate. Also referred to as 'global climate change’.
Climate Model
A quantitative way of representing the interactions of the atmosphere, oceans, land surface, and ice. Models can range from relatively simple to quite comprehensive.
Cloud
A visible mass of condensed water vapor particles or ice suspended above the Earth's surface. Clouds may be classified on their visual appearance, height, or form.
Condensation
The change of water vapor into a liquid. In order to condense water vapor, the air must be at or near saturation in the presence of condensation nuclei.
Conduction
The transfer of heat from one molecule to another or from one substance to another.
Controls
Experiments performed where the outcome is already known. These are tests done to verify one's procedure before making changes to the experiment.
Convection
Generally, transport of heat and moisture by the movement of a fluid. In fluid mechanics, convection refers to flow driven by buoyancy. In meteorology, the term is used specifically to describe vertical transport of heat and moisture in the atmosphere, especially by updrafts and downdrafts in an unstable atmosphere. The terms "convection" and "thunderstorms" often are used interchangeably, although thunderstorms are only one form of convection. Cbs, towering cumulus clouds, and ACCAS clouds all are visible forms of convection. However, convection is not always made visible by clouds. Convection which occurs without cloud formation is called dry convection, while the visible convection processes referred to above are forms of moist convection. (National Weather Service +)
Convective Storms
Storms created by rising warm air, thunderstorms.
Coriolis Force
The deflection of moving objects (air and water currents) due to the rotation of the Earth--to the right in the northern hemisphere, and to the left in the southern. (JPL)
Cyclone
An area of low pressure around which the winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. It is usually associated with stormy weather
Data
Observations, values recorded by people or taken from instruments for example; time, temperature, amount of precipitation.
Dead Reckoning
Early navigators used dead reckoning to go from port to port, or across a lake. First they plotted their location based on the positions of the stars, moon, and sun, then determined their destination based on their speed and compass direction.
Deviation
Given data values and its calculated mean value, the deviation is found by finding the difference between the mean value and a data value.
Doldrums
The regions on either side of the equator where air pressure is low and winds are light. (National Weather Service)
Doppler Effect
A perceived shift in the frequency of an electromagnetic or sound wave due to the relative movement of the source or the observer.
Easterlies
The east to west winds that prevail over the tropics and polar regions in both hemispheres.
Eddy
A rotating water current that runs contrary to the main current. Eddies can average up to a few hundred kilometers in diameter, contain up to 5,000 cubic kilometers of water, and last several years. They can be cyclonic or anticyclonic, and the Coriolis force determines their rotation. (JPL)
El Niño
warm-water conditions off the western tropical coasts of the Americas, occurring irregularly but usually around Christmastime, caused by weakening trade winds and causing depleted fisheries, heavier-than-normal rain in the central and eastern Pacific, and drought in the western Pacific. (JPL)
El Niño, Southern Oscillation (ENSO)
An interannual seesaw in tropical sea-level pressure between the Eastern and Western Hemispheres. During El Niño, unusually high atmospheric sea-level pressures develop in the western tropical Pacific and Indian Ocean regions, and unusually low sea-level pressures develop in the southeastern tropical Pacific. So tendencies for unusually low pressures west of the date line and high pressures east of the date line have also been linked to periods of anomalously cold equatorial Pacific sea-surface temperatures sometimes referred to as La Niña. (JPL)
Energy Flux
The rate of energy flow across a defined area.
Equator
The Equator is an imaginary great circle on the Earth's surface, everywhere equally distant from the two poles, dividing Earth's surface into the Northern and Southern Hemispheres. (Webster)
Geostrophic Flow
Currents flow along contours of constant pressure, rather than from high to low pressure. The pressure gradient force (at right angles to the geostrophic velocity vector) is balanced by the Coriolis force due to the Earth's rotation; the Coriolis force is at right angles to the velocity vector, and equal and opposite to the pressure gradient force. Contours of constant pressure are streamlines for the geostrophic flow.
Global Warming
Global warming is a long-term increase in the global-average surface temperature of Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is often used to describe the warming predicted to occur as a result of increased emissions of greenhouse gases. Scientists generally agree that Earth's surface has warmed by about 1 degree Fahrenheit in the past 140 years. The Intergovernmental Panel on Climate Change (IPCC) recently concluded that increased concentrations of greenhouse gases are causing an increase in Earth's surface temperature and that increased concentrations of sulfate aerosols have led to relative cooling in some regions, generally over and downwind of heavily industrialized areas.
Gulf Stream
The Gulf Stream is a warm western boundary current flowing northward off the eastern coast of North America from the Bahamas to the Grand Banks off of Newfoundland.
Gyre
The slow averaged flow of water around an ocean basin centered on subtropical high-pressure regions, with circulation clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
Hadley Cell
A thermally driven, global band of rotating air approximately 30° latitude in width, in both the northern and southern hemispheres, that drives weather systems and controls climate. (JPL)
Hurricane
A tropical cyclone with surface winds in excess of 32 m/s (64 knots or 74 mph) in the Western Hemisphere. There are various regional names for these storms. (National Weather Service)
Hypothesis
A hypothesis is a proposed explanation for an observation or phenomena that can be tested through experimentation.
Independent Variable
In experimentation, this is the variable under the control of the
investigator. This variable is manipulated to understand the behavior of the system one is exploring.
Infrared Satellite Imagery
This satellite imagery senses surface and cloud top temperatures by measuring the wavelength of electromagnetic radiation emitted from these objects. This energy is called "infrared". High clouds are very cold, so they appear white. Mid-level clouds are somewhat warmer, so they will be a light gray shade. Low cloud are warmer still, so they appear as a dark shade of gray or black. Often, low clouds are the same temperature as the surrounding terrain and cannot be distinguished at all. The satellite picks up this infrared energy between 10.5 and 12.6 micrometer (um) channels. (National Weather Service)
Isothermal Layer
A layer of the ocean or atmosphere in which the temperature is constant.
Intertropical Convergence Zone
(abbrev. ITCZ) The boundary zone separating the northeast trade winds of the Northern Hemisphere from the southeast trade winds of the Southern Hemisphere. The region where the northeasterly and southeasterly tradewinds converge, forming an often continuous band of clouds or thunderstorms near the equator. (National Weather Service)
Joule
A unit of work or energy equal to 107 ergs, and practically the energy expended in one second by an electric current of one ampere in a resistance of one ohm. (Webster)
A 100-watt light bulb uses 100 joules every second. Measuring joules allows the comparison of energy needs, capacities, and efficiencies. For example, all of the world's humanity used 31.5 x 1018 joules of electrical, mechanical, fossil fuel and heat energy in 1990.
Kelvin Wave
An eastward-moving ocean wave that crosses the equatorial Pacific in about 2 months. (JPL)
Kinetic Energy
The energy of an object due to its motion.
Kuroshio Current
The Kuroshio current is the warm western boundary current flowing northeastward from Taiwan along the eastern coast of Japan to the northern Pacific. Also called the Japan Current.
La Niña
Cold-water conditions off the western tropical coasts of the Americas, occurring irregularly and occasionally following El Niño conditions, caused by stiffening trade winds. It results in regenerated fisheries, drought in the central and eastern Pacific, and rain in the western Pacific. (JPL)
Laminar Flow
The smooth and regular flow of a fluid in a constant direction without any mixing taking place.
Latent Heat
Heat energy required to change a substance from one state to another. It is the energy stored when water evaporates into vapor or ice melts into liquid. It is released as heat when vapor condenses or water freezes.
Latitude
The location north or south in reference to the equator, which is designated at zero (0) degrees. Lines of latitude are parallel to the equator and circle the globe. The North and South poles are at 90 degrees North and South latitude. (National Weather Service)
Longitude
The location east or west in reference to the Prime Meridian, which is designated as zero (0) degrees longitude. The distance between lines of longitude are greater at the equator and smaller at the higher latitudes, intersecting at the Earth's North and South Poles. Time zones are correlated to longitude. (National Weather Service)
Magnetic Declination
The observed angular distance between magnetic north on a compass and true north.
Mean
The arithmetic average of a set of data (numbers), or the middle point between its two extremes. (National Weather Service)
Median
A statistical analysis representing the value of the "middle" in a rank-ordered set of observations. It divides the group of observations into two equal groups.
Meridional Overturning Circulation
The global cycling of water from surface currents to deepwater currents. Winds, the Coriolis effect, and density differences (thermohaline circulation) drive it. Meridional refers to its north to south orientation, especially in the Atlantic Ocean.
Microwave
Electromagnetic radiation with a wavelength of between 0.3 and 30 centimeters (between infrared and radio), corresponding to a frequency of 1 to 100 gigahertz. It is favored for radar because of its cloud-penetrating properties. (JPL)
Mixed layer
The top layer of the ocean in which wind and convection stir it up, creating uniform temperature and salinity.
Modeling
An investigative technique that uses a mathematical or physical representation of a system such as ocean circulation or climate to explore its characteristics and limits. Many models (or system representations) are programmed as computer simulations of causes and effects within the system. These models are often used to test the effects of changing variables on the system. For example, models of global or regional climate may be used to attempt to simulate the effects on temperature of a change in the concentration of greenhouse gas emissions.
North Atlantic Current
The continuation of the Gulf Stream in the North Atlantic, starting at the Grand Banks and flowing northeast towards Northwest Europe.
Oceanography
The study of the ocean, embracing and integrating all knowledge pertaining to the ocean's physical boundaries, the chemistry and physics of sea water, and marine biology. (National Weather Service)
Precipitation
The process where water vapor condenses in the atmosphere to form water droplets that fall to the Earth as rain, sleet, snow, hail, etc. (National Weather Service)
Radar
A system using beamed and reflected radio-frequency radiation, usually microwave, to detect objects and measure ranges. (JPL)
Radiation
Energy transport through electromagnetic waves. (National Weather Service)
Rossby Waves
An extraordinarily slow westward-moving ocean wave of low amplitude (10 to 20 centimeters) and great width (hundreds of kilometers) that crosses the Pacific over several decades. (JPL)
Salinity
Salinity is the total amount of dissolved material in grams in one kilogram of sea water. (Stewart)
Satellite
A small heavenly body revolving around a larger one. A human-made object put into orbit around the Earth, moon and other planets.
Scatterometer
A microwave (radar) sensor that scans the surface of the earth from an aircraft or satellite and reads the reflection or scattering coefficient of the return pulse to measure surface roughness and derive wind speed and direction. (JPL)
Sea Surface Height (SSH)
Sea surface height is defined as the distance of the sea surface above the reference ellipsoid. The sea surface height is computed from altimeter range and satellite altitude above the reference ellipsoid. The "reference ellipsoid" is the first-order definition of the non-spherical shape of the Earth as an ellipsoid of revolution with equatorial radius of 6378.1363 kilometers and a flattening coefficient of 1/298.257. Sea surface height is often shown as a sea-surface anomaly or sea-surface deviation, this is the difference between the sea surface height at the time of measurement and the average sea surface height for that region and time of year. (JPL)
Sea Surface Height
the variable height of the sea surface above or below the geoid. (JPL)
Sea Surface Temperature (SST)
The temperature of the layer of seawater (approximately 0.5 m deep) nearest the atmosphere.
Sensible Heat Flux
The flux of heat from the earth's surface to the atmosphere that is not associated with phase changes of water; a component of the surface energy budget. (National Weather Service)
Solar Radiation
Energy from the Sun. Also referred to as short-wave radiation. Of importance to the climate system, solar radiation includes ultra-violet radiation, visible radiation, and infrared radiation.
Thermocline
The boundary between the warm upper layer and the colder deeper layer in a body of water.
Thermohaline
As one descends from the surface of the ocean, the temperature remains nearly the same as it was at the surface, but at a certain depth temperature starts decreasing rapidly with depth. This boundary is called the thermocline. In studying the tropical Pacific Ocean, the depth of 20ºC water ("the 20ºC isotherm") is often used as a proxy for the depth of the thermocline. Along the equator, the 20ºC isotherm is typically located at about 50 m depth in the eastern Pacific, sloping downwards to about 150 m in the western Pacific. (National Weather Service)
Tides
The periodic (occurring at regular intervals) variations in the surface water level of the oceans, bays, gulfs, and inlets. Tides are the result of the gravitiational attraction of the sun and the moon on the earth. The attraction of the moon is far greater than the attraction of the sun due to the close proximity of the earth and the moon. The sun is 360 times further from the earth than the moon. Therefore, the moon plays a larger role than the sun in producing tides. Every 27.3 days, the earth and the moon revolve around a common point. This means that the oceans and other water bodies which are affected by the earth-moon system experience a new tidal cycle every 27.3 days. Because of the physical processes which occur to produce the tidal system, there are two high tides and two low tides each day. Because of the angle of the moon with respect to the earth, the two high tides each day do not have to be of equal height. The same holds true for the two low tides each day. Tides also differ in height on a daily basis. The daily differences between tidal heights is due to the changing distance between the earth and the moon. Scientists use measurements of the height of the water level to examine tides and the various phenomena which influence tides, such as hurricanes and winter storms. (National Weather Service)
Trade Winds
The trade winds are a pattern of wind found in bands around Earth's equatorial region. The trade winds are the prevailing winds in the tropics, blowing from the high-pressure area in the horse latitudes towards the low-pressure area around the equator. The trade winds blow predominantly from the northeast in the northern hemisphere and from the southeast in the southern hemisphere. (JPL)
Turbulence
The irregular, seemingly random movement of fluids such as the air and atmosphere.
Upwelling
The vertical motion of water in the ocean by which subsurface water of lower temperature and greater density moves toward the surface of the ocean. Upwelling occurs most commonly among the western coastlines of continents, but may occur anywhere in the ocean. Upwelling results when winds blowing nearly parallel to a continental coastline transport the light surface water away from the coast. Subsurface water of greater density and lower temperature replaces the surface water, and exerts a considerable influence on the weather of coastal regions. Carbon dioxide is transferred to the atmosphere in regions of upwelling. This is especially important in the Pacific equatorial regions, where 1-2 GtC/year may be released to the atmosphere. Upwelling also results in increased ocean productivity by transporting nutrient-rich waters to the surface layer of the ocean.
Variability
When used in reference to climate, variability refers to the tendency of conditions to vary around some reference point (such as the tendency of the temperature to deviate from some average).
Vector
An arrow that represents a physical process such as an ocean current. The length represents the magnitude and the direction it points represents the direction of the process.
Walker Circulation
The atmospheric circulation over the equatorial Pacific in which surface winds blow from high pressure in the east to low pressure in the west. The air then rises at the area of low pressure, returns east, and descends at the area of high pressure.
Wavelength
Is a measure of the length of from crest to crest or trough to trough of a wave. Watt a common unit used in measuring power. Power is defined as the flow of energy over time. A watt is equivalent to 3.41 Btu/hour or one joule per second. Where an "e" follows the unit (as in kwe or Mwe), the watt is in the form of electrical energy. Where a "t" follows the unit (as in kwt or Mwt), the watt is in the form of thermal energy.
Weather
The specific condition of the atmosphere at a particular place and time. It is measured in terms of such things as wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation. In most places, weather can change from hour-to-hour, day-to-day, and season-to-season.
Westerlies
The west to east winds that prevail over the mid-latitudes in the northern and southern hemispheres. |
