Differential RotationIn solar-terrestrial terms, the change in solar rotation rate with latitude. Low latitudes rotate at a faster angular rate (approx.
Diffuse IcePoorly defined ice edge limiting an area of dispersed ice; usually on the leeward side of an area of floating ice.
diffuse insolationThe solar radiation that is scattered or reflected by atmospheric components (e.g., clouds) to the earth's surface.
diffuse shortwave irradianceAll of the solar radiation, across the wavelength range of 0.4 and 4 µm, coming directly from the sky except for solar radiation coming directly from the…
diffuse spectral irradianceThe narrow spectral range of measurements coming directly from the sky except for solar radiation coming directly from the sun whose wavelength falls…
Difluence(or diffluence) - A pattern of wind flow in which air moves outward (in a "fan-out" pattern) away from a central axis that is oriented parallel to the…
DIR1. Direction 2. On a buoy report, the ten-minute average wind direction measurements in degrees clockwise from true North.
Direct Flood DamageThe damage done to property, structures, goods, etc., by a flood as measured by the cost of replacement and repairs.
Direct HitA close approach of a tropical cyclone to a particular location. For locations on the left-hand side of a tropical cyclone's track (looking in the…
direct insolationThe solar radiation that is transmitted directly through the atmosphere to the earth's surface without interacting with atmospheric components.
Direct RunoffWater that flows over the ground surface or through the ground directly into streams, rivers, or lakes.
direct shortwave irradianceRadiant energy, across the wavelength range of 0.4 and 4 µm, that is transferred directly from the sun to the receiver.
Direct Solar RadiationThe component of solar radiation received by the earth's surface only from the direction of the sun's disk (i.e.
direct spectral irradianceThe narrow spectral range of measurements coming directly from the sun whose wavelength falls within the solar range of 0.4 and 4 µm.
Directional ShearThe component of wind shear which is due to a change in wind direction with height, e.g., southeasterly winds at the surface and southwesterly winds aloft.
Disappearing Solar Filament (DSF)In solar-terrestrial terms, the sudden (timescale of minutes to hours) disappearance of a solar filament (prominence).
Discharge(DIS-charj) In medicine, a fluid that comes out of the body. Discharge can be normal or a sign of disease.
Discharge CurveA curve that expresses the relation between the discharge of a stream or open conduit at a given location and the stage or elevation of the liquid surface…
Discharge Table(1) A table showing the relation between two mutually dependant quantities or variable over a given range of magnitude.
DisdrometerEquipment that measures and records the size distribution of raindrops.
diskThe visible surface of the sun (or any heavenly body) projected against the sky.
DispersionDistortion of the shape of a seismic-wave train because of variation of velocity with frequency.
Distillate fuel oilProducts of refinery distillation sometimes referred to as middle distillates; kerosene, diesel fuel, and home heating oil. No.
Distribution (Hydro)GraphA unit hydrograph of direct runoff modified to show the proportions of the volume of runoff that occur during successive equal units of time.
Diurnal CyclesVariations in meteorological parameters such as temperature and relative humidity over the course of a day which result from the rotation of the Earth…
Diurnal Temperature RangeThe temperature difference between the minimum at night (low) and the maximum during the day (high).
divergenceThe expansion or spreading out of a vector field; usually said of horizontal winds. It is the opposite of convergence.
DiversionThe process of removing some minor criminal, traffic or juvenile cases from the full judicial process, on the condition that the accused undergo some sort…
DivideA ridge or high area of land that separates one drainage basin from another.
Dividing StreamlineIn the blocked flow region upwind of a mountain barrier, the streamline that separates the blocked flow region near the ground from the streamlines above…
Dividing Streamline HeightThe height above ground of the dividing streamline, as measured far upwind of a mountain barrier. See dividing streamline.
DoldrumsThe regions on either side of the equator where air pressure is low and winds are light.
DolomiteA magnesium-rich carbonate sedimentary rock. Also, a magnesium-rich carbonate mineral (CaMgCO3).
DomainA sub-network of servers and computers within a LAN. Domain information is useful when restoring backup tapes, particularly of email.
Domestic ConsumptionThe quantity, or quantity per capita, of water consumed in a municipality or district for domestic uses or purposes during a given period, generally one…
Domestic Use of waterThe use of water primarily for household purposes, the watering of livestock, the irrigation of gardens, lawns, shrubbery, etc.
Doppler RadarRadar that can measure radial velocity, the instantaneous component of motion parallel to the radar beam (i.e., toward or away from the radar antenna).
doppler velocity (m/s)(m/s)When used, the positive is down (towards the radar). Particle and air motions contribute to the velocity.
Down-Valley WindA thermally driven wind directed down a valley's axis, usually occurring during nighttime; part of the along-valley wind system.
DownburstA strong downdraft current of air from a cumulonimbus cloud, often associated with intense thunderstorms.
Downdraft(Abbrev. DWNDFT) - A small-scale column of air that rapidly sinks toward the ground, usually accompanied by precipitation as in a shower or thunderstorm.
Downslope FlowA thermally driven wind directed down a mountain slope and usually occurring at night; part of the along-slope wind system.
downstreamThe region extending in a 3' direction from a gene.
Downstream SlopeThe slope or face of the dam away from the reservoir water. This slope requires some kind of protection (e.g.
DownwashA deflection of air downward relative to an object that causes the deflection.
downwelling longwave irradianceThe total diffuse and direct radiant energy, at wavelengths longer than approximately 4 µm, that is being emitted downwards.
Downwelling RadiationThe component of radiation directed toward the earth's surface from the sun or the atmosphere, opposite of upwelling radiation.
downwelling shortwave irradianceThe total diffuse and direct radiant energy that comes from some continuous range of directions, at wavelengths between 0.
DRDiminishing Returns. Used to describe something that reduces slowly over time on consecutive repetitions of the same action.
Drainage AreaThe area which drains to a particular point on a river or stream. The drainage area of a stream at a specified location is that area, measured in a…
Drainage BasinAll of the area drained by a river system. The drainage basin is a part of the surface of the earth that is occupied by a drainage system, which consists…
Drainage DensityThe relative density of natural drainage channels in a given area. It is usually expressed in terms of miles of natural drainage or stream channel per…
Drainage DivideThe boundary line, along a topographic ridge or along a subsurface formation, separating two adjacent drainage basins.
DrainerA valley or basin from which air drains continuously during nighttime rather than becoming trapped or pooled.
Drains (Relief Wells)A vertical well or borehole, usually downstream of impervious cores, grout curtains or cutoffs, designed to collect and direct seepage through or under a…
DrawdownLowering a lake level for a specific purpose.
Drift of iceDrift of ice Displacement of a sea ice field from its place of origin under the effect of ocean currents and winds.
Drifting buoyDrifting buoy Floating (or drifting on ice) ocean buoy equipped with meteorological and/or oceanographic sensing instruments linked to transmitting…
Drifting IcePieces of floating ice moving under the action of wind and/ or currents.
Drifting SnowDrifting snow is an uneven distribution of snowfall/snow depth caused by strong surface winds. Drifting snow may occur during or after a snowfall.
Drifting stationsDrifting stations (drifting ice stations) Research stations on the floes of the Arctic Ocean.
DrizzlePrecipitation consisting of numerous minute droplets of water less than 0.5 mm (500 micrometers) in diameter.
Drop-size DistributionThe distribution of rain drops or cloud droplets of specified sizes.
DroughtClimatic condition in which there is insufficient soil moisture available for normal vegetative growth. A prolonged period of below-average precipitation.
Drought AssessmentsAt the end of each month, CPC issues a long-term seasonal drought assessment. On Thursdays of each week, the CPC together with NOAA National Climatic Data…
Drought IndexComputed value which is related to some of the cumulative effects of a prolonged and abnormal moisture deficiency.
Dry AdiabatA line of constant potential temperature on a thermodynamic chart.
Dry Adiabatic Lapse RateThe rate at which the temperature of a parcel of dry air decreases as the parcel is lifted in the atmosphere.
dry adiabatic lapse rate (DALR)(DALR)The rate at which the temperature of a parcel of dry air decreases as the parcel is lifted in the atmosphere. The dry adiabatic lapse rate is 5.
Dry CrackCrack visible at the surface but not going right through the ice cover, and therefore it is dry.
Dry FloodproofingIn hydrologic terms, a dry floodproofed building is sealed against floodwaters. All areas below the flood protection level are made watertight.
Dry LineA boundary separating moist and dry air masses, and an important factor in severe weather frequency in the Great Plains.
Dry Line BulgeA bulge in the dry line, representing the area where dry air is advancing most strongly at lower levels.
Dry Line StormAny thunderstorm that develops on or near a dry line.
Dry MicroburstA microburst with little or no precipitation reaching the ground; most common in semi-arid regions. They may or may not produce lightning.
Dry Punch[Slang], a surge of drier air; normally a synoptic-scale or mesoscale process. A dry punch at the surface results in a dry line bulge.
Dry SlotA zone of dry (and relatively cloud-free) air which wraps east- or northeastward into the southern and eastern parts of a synoptic scale or mesoscale low…
Dry ThunderstormGenerally a high-based thunderstorm when lightning is observed, but little if any precipitation reaches the ground.
Dry Weather FlowStreamflow which results from precipitation that infiltrates into the soil and eventually moves through the soil to the stream channel.
Dry-adiabatic1. An adiabatic process in a hypothetical atmosphere in which no moisture is present. 2.