QuikSCAT

A NASA satellite that is providing climatologists, meteorologists and oceanographers with daily, detailed snapshots of the winds swirling above the world's oceans. QuikSCAT carries a state-of-the-art radar instrument called a scatterometer. Known as "SeaWinds," this scatterometer operates by transmitting high-frequency microwave pulses to the ocean surface and measuring the "backscattered" or echoed radar pulse bounced back to the satellite. The instrument senses ripples caused by winds near the ocean's surface, from which scientists can compute the winds' speed and direction. The instruments can acquire hundreds of times more observations of surface wind velocity each day than can ships and buoys, and are the only remote-sensing systems able to provide continuous, accurate and high-resolution measurements of both wind speeds and direction regardless of weather conditions. The instrument is currently collecting data over ocean, land, and ice in a continuous 1,800-kilometer-wide band, making approximately 400,000 measurements and covering 90% of Earth's surface each day. See QuikSCAT fact sheet.

R&D

Research and Development.

radar interferometry

The study of interference patterns caused by radar signals; a technique that enables scientists to generate three dimensional images of the Earth's surface.

radiant

1. In optics, the point or object from which light proceeds. 2. In geometry, a straight line proceeding from a given point, or fixed pole, about which it is conceived to revolve. 3. In astronomy, the point in the heavens from which a shower of meteors seems to proceed.

radiation

Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object.

radiation budget

A measure of all the inputs and outputs of radiative energy relative to a system, such as Earth. See Earth Radiation Budget Experiment.

radiative cooling

Cooling process of the Earth's surface and adjacent air, which occurs when infrared (heat) energy radiates from the surface of the Earth upward through the atmosphere into space. Air near the surface transfers its thermal energy to the nearby ground through conduction, so that radiative cooling lowers the temperature of both the surface and the lowest part of the atmosphere.

radiative forcing

A change in the balance between incoming solar radiation and outgoing infra-red radiation. Without any radiative forcing, solar radiation coming to the Earth would continue to be approximately equal to the infra-red radiation emitted from the Earth. The addition of greenhouse gases traps and increased fraction of the infra-red radiation, reradiating it back toward the surface and creating a warming influence (i.e., positive radiative forcing because incoming solar radiation will exceed outgoing infra-red radiation).

radiative transfer

Theory dealing with the propagation of electromagnetic radiation through a medium.

radio spectrum

The complete range of frequencies or wave lengths of electromagnetic waves, specifically those used in radio and television.

radio wave

An electrical impulse sent through the atmosphere at radio frequency.

radioactive

Giving off or capable of giving off radiant energy in the form of particles or rays, as in alpha, beta, and gamma rays.

radiometer

An instrument that quantitatively measures electromagnetic radiation. Weather satellites carry radiometers to measure radiation from snow, ice, clouds, bodies of water, the Earth's surface, and the sun.

radiosonde

A balloon-borne instrument that measures meteorological parameters from the Earth's surface up to 20 miles in the atmosphere. The radiosonde measures temperature, pressure, and humidity, and transmits or 'radios' these data back to Earth. Upper air winds also are determined through tracking of the balloon ascent.

Radiosonde observations generally are taken twice a day (0000 and 1200 UTC) around the globe. NOAA's National Weather Service (NWS) operates a network of about 90 radiosonde observing sites in the U.S. and its territories. When the balloons burst, radiosondes return to Earth on a parachute. Approximately 25 percent are recovered and returned to NWS for reconditioning and reuse.

rain forest

An evergreen woodland of the tropics distinguished by a continuous leaf canopy and an average rainfall of about 100 inches per year. Rain forests play an important role in the global environment. The Earth sustains life because of critical balances and interactions among many factors. Were there not processes at work that limit the effects of other essential processes, Earth would become uninhabitable. Destruction of tropical rain forests reduces the amount of leaf area in the tropics, and consequently the amount of carbon dioxide absorbed, causing increases in levels of carbon dioxide and other atmospheric gases. It is estimated that cutting and burning of tropical forests contributes about 20 percent of the carbon dioxide added to the atmosphere each year. The World Resources Institute and the International Institute for Environment and Development have reported that the world's tropical forests are being destroyed at the rate of fifty-four acres per minute, or twenty-eight million acres lost annually. Rain forest destruction also means the loss of a wide spectrum of biological life, erosion of soil, and possible desertification.

rain gauge

Calibrated container that measures the amount of rainfall during a specific period of time.

real time

As it happens.

reflection

The return of light or sound waves from a surface. If a reflecting surface is plane, the angle of reflection of a light ray is the same as the angle of incidence.

relative humidity

The ratio of the amount of water vapor in the air compared to the amount required for saturation (at a particular temperature and pressure).

remote sensing

The technology of acquiring data and information about an object or phenomena by a device that is not in physical contact with it. In other words, remote sensing refers to gathering information about the Earth and its environment from a distance, a critical capability of the Earth Observing System.

For example, spacecraft in low-Earth orbit pass through the outer thermosphere, enabling direct sampling of chemical species there. These samples have been used extensively to develop an understanding of thermospheric properties. Explorer-17, launched in 1963, was the first satellite to return quantitative measurements of gaseous stratification in the thermosphere. However, the mesosphere and lower layers cannot be probed directly in this way--global observations from space require remote sensing from a spacecraft at an altitude well above the mesopause. The formidable technological challenges of atmospheric remote sensing, many of which are now being overcome, have delayed detailed study of the stratosphere and mesosphere by comparison with thermospheric research advances.

Some remote-sensing systems encountered in everyday life include the human eye and brain, and photographic and video cameras.

resolution

A measure of the ability to separate observable quantities. In the case of imagery, it describes the area represented by each pixel of an image. The smaller the area represented by a pixel, the more accurate and detailed the image.

respiration

The process by which animals use up stored foods (by combustion with oxygen) to produce energy.

retrograde orbit

An east-to-west orbit of Earth (Earth spins west to east). See prograde orbit.

revolution

Process of the Earth circling the sun in its orbit. Revolution determines the seasons, and the length of the year. In addition, differences in seasons occur because of Earth's inclination (tilt on its axis) of about 23.5 degrees as it revolves around the sun. Compare with rotation.

rotation

Process of the Earth turning on its axis. Rotation determines day and night, and the length of the day. Compare with revolution.