Radar frequency band-
A frequency band of microwave radiation within which radars operate. The radar frequency bands were first designated by code letters for secrecy during World War II; these letters are still in common use, although the exact frequency intervals to which they apply have undergone some redefinition.
Radial velocity-
The component of a three dimensional velocity vector oriented along the radial direction from the origin point or axis in polar, cylindrical, or spherical coordinates. In connection with Doppler radar, the radial velocity component is called Doppler velocity.
Radiance-
A radiometric term for the rate at which radiant energy in a set of directions confined to a unit solid angle around a particular direction is transferred across unit area of a surface (real or imaginary) projected onto this direction.
Radiant energy-
Infrequently, any energy propagated by a physical quantity governed by a wave equation.
Radiant flux-
Radiant energy per unit time passing some specified area from one side.
Radiational cooling-
In meteorology, the result of radiative cooling of the earths surface and adjacent air. Radiational cooling occurs, as is typical on calm, clear nights
Radiation fog-
A common type of fog, produced over a land area when radiational cooling reduces the air temperature to or below its dewpoint.
Radiative forcing-
In radiation, the net flux of radiation into or out of a system. As a consequence of radiative forcing there must be some change to the nonradiative energy states of the system.
Rainband-
The complete cloud and precipitation structure associated with an area of rainfall sufficiently elongated that an orientation can be assigned.
Rain shadow-
A region of sharply reduced precipitation on the lee side of an orographic barrier, as compared with regions upwind of the barrier.
Rayleigh scattering-
Approximate theory for electromagnetic scattering by small particles.
Reflectance-
A general term referring to the radiation reflected from, or scattered back through, a given surface in response to radiation incident on the surface with the same wavelength or wavelength range.
Refraction-
A change of direction and possibly amplitude of an electromagnetic, acoustic, or any other wave propagating in a material medium, homogeneous on the scale of the wavelength, as a consequence of spatial variation in the properties of the medium.
Relative vorticity-
The vorticity as measured in a system of coordinates fixed on the earths surface.Usually, only the vertical component of the vorticity is meant.
Residual layer-
The middle portion of the nocturnal atmospheric boundary layer characterized by weak sporadic turbulence and initially uniformly mixed potential temperature and pollutants remaining from the mixed layer of the previous day.
Return stroke-
The intense luminosity that propagates upward from earth to cloud base in the last phase of each lightning stroke of a cloud to ground discharge.
Rime-
A white or milky and opaque granular deposit of ice formed by the rapid freezing of supercooled water drops as they impinge upon an exposed object.
Roll cloud-
A low level, horizontal, tube shaped arcus cloud associated with a gust front of a convective storm or occasionally a cold front.
Roughness sublayer-
Same as transition layer. The lowest atmospheric layer immediately adjacent to a surface covered with relatively large roughness elements such as stones, vegetation, trees, or buildings.
Rossby wave-
A wave on a uniform current in a two dimensional nondivergent fluid system, rotating with varying angular speed about the local vertical (beta plane).
