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Radar altimetry
Radar altimetry is a satellite remote sensing technique that times microwave pulses to measure sea surface, ice, and land heights, underpinning sea level monitoring and oceanography.
Radar interferometry
Radar interferometry (InSAR) is a remote sensing technique that combines radar signals from two antennas, or one antenna on repeated passes, to measure terrain elevation and surface deformation.
Radar meteorology
Radar meteorology is the branch of meteorology that uses radars for weather observations and forecasts; modern Doppler radars also measure wind motion within storms, aiding severe weather warnings.
Radar reflectivity factor
The radar reflectivity factor (Z) measures the power a weather radar receives back from raindrops, snowflakes, and ice particles, usually shown on the logarithmic dBZ scale.
Radiative equilibrium
Radiative equilibrium is the state of a planetary atmosphere in which net radiative heating is zero at every level, first formulated by Karl Schwarzschild in 1906.
Radiative forcing
Radiative forcing, also called climate forcing, is the change in Earth's energy balance from an external driver such as carbon dioxide, measured in watts per square meter.
Radiocarbon dating
Radiocarbon dating, also called carbon-14 dating, is a method that determines the age of carbon-bearing materials by measuring their carbon-14 content, usable back about 50,000 years.
Radiolarite
Radiolarite is a hard siliceous sedimentary rock made of radiolarian skeletons, the lithified equivalent of radiolarian ooze, and a raw material for prehistoric stone tools.
Radiometric dating
Radiometric dating, also called radioactive dating, is a family of techniques that determine the age of rocks and materials by measuring radioactive isotopes and their decay products at known rates.
Radiosonde
A radiosonde, also called a rawinsonde or balloon sonde, is a balloon-borne instrument measuring pressure, temperature, and humidity up to 35 km, invented in 1929 and launched twice daily worldwide.
Radius of influence
The radius of influence of a pumping well is the maximum distance up to which pumping significantly affects the aquifer, a concept used in wellhead protection and permitting.
Radius of maximum wind
The radius of maximum wind (RMW) is the distance from a tropical cyclone's center to its maximum winds, generally at the inner edge of the eyewall in strong hurricanes.
Rain
Rain, also called a rain storm, is precipitation in which liquid water drops larger than 0.5 mm fall from a cloud; smaller, closely spaced drops are drizzle.
Rain gauge
A rain gauge is an instrument that measures rainfall by collecting water over a known area and reporting it as depth, serving as the reference for calibrating radar and satellite estimates.
Rain of animals
A rain of animals, also called raining animals, is a reported weather event where fish or frogs fall from the sky, explained by tornadoes and waterspouts.
Rain shadow
A rain shadow, also called the rain shadow effect, is a region of reduced precipitation on the lee side of a mountain, where descending air warms and dries.
Rainband
A rainband, also called a spiral band, is a curved band of clouds and thunderstorms spiraling outward from a tropical cyclone's eyewall, producing heavy rain, wind, and tornadoes.
Rainmaking
Rainmaking, also called artificial rain or pluviculture, is the attempt to produce or increase rainfall, practiced historically as ritual and today as cloud seeding, which began in 1946.
Raised bog
A raised bog is an ombrotrophic peatland, a dome of peat raised above the groundwater by its own growth, fed only by rain, acidic, and dominated by Sphagnum peat mosses.
Rajendra K. Pachauri
Rajendra Kumar Pachauri, known as R.K. Pachauri, was an Indian engineer and economist who led TERI in New Delhi and chaired the IPCC from 2002 to 2015.
Rajendra Singh (राजेन्द्र सिंह)
Rajendra Singh (राजेन्द्र सिंह), born 1959, is an Indian water conservationist known as the "Waterman of India" who leads rainwater harvesting and river rejuvenation in rural Rajasthan.
Ralph Emery
Ralph Emery, born Walter Ralph Emery, was an American broadcaster known as the dean of country music broadcasting, inducted into the Country Music Hall of Fame in 2007.
RAMS (atmospheric model)
RAMS, the Regional Atmospheric Modeling System, is a numerical atmospheric model developed at Colorado State University, formed in 1986 by merging cloud and mesoscale models.
Ranakah
Ranakah, also called Anak Ranakah, is a lava-dome cluster on western Flores, Indonesia, whose youngest dome formed in a surprise VEI 3 eruption beginning 28 December 1987 after no recorded prior activity; last erupted 1991, alert level 2 since September 2026.
Rangeland
Rangeland is land with natural grasses, shrubs, or scattered trees suitable for grazing, managed through ecological processes rather than cultivation, and covering over half of Earth's land.
Rano Raraku
Rano Raraku, also known as Maunga Eo, is a volcanic tuff cone on Easter Island, Chile, and the quarry for nearly all of the island's moai statues.
RAPID array
The RAPID array, also known as the RAPID-MOCHA-WBTS array, is a system of ocean moorings across the Atlantic at 26.5°N that has continuously measured the strength of the Atlantic Meridional Overturning Circulation since 2004.
Rapid intensification
Rapid intensification is a fast increase in a tropical cyclone's maximum sustained winds of at least 30 knots in 24 hours, producing the strongest storms and largest forecast errors.
Rapid Refresh
The Rapid Refresh (RAP) is NOAA's continental-scale weather analysis and forecast system covering North America, updated every hour and run operationally since it replaced the Rapid Update Cycle in 2012.
Rapid Refresh Forecast System
The Rapid Refresh Forecast System (RRFS) is NOAA's next-generation convection-allowing weather prediction system, covering North America at 3 km and replacing several National Weather Service regional models in 2026.