The combining of diverse data, possibly sampled at different times and intervals and different locations, into a unified and consistent description of a physical system, such as the state of the atmosphere. One or more data assimilation techniques are often used during the initialization of an atmosphere or ocean forecast model. Source: (c) 1999, American Meteorological Society. Used with permission.

A clause in an insurance policy that relieves the insurer of responsibility to pay the initial loss up to a stated amount.

The removal of leaves off a tree.

The Digital Flood Insurance Rate Map (DFIRM) is comprised of all digital data required to create the hardcopy FIRM. This includes base map information, graphics, text, shading, and other geographic and graphic data required to create the final hardcopy FIRM product to FEMA standards and specifications. These data serve the purpose of map design and provides the database from which the Digital Line Graph thematic product of the flood risks can be extracted to create the DFIRM-DLG. These products are generally produced in a countywide format. DFIRMs are subjected to community review and approval and are, therefore, the official basis for implementing the regulations and requirements of the NFIP within the community. Source: ABAG.ca.gov

A close approach of a tropical cyclone to a particular location. For locations on the left-hand side of a track of a tropical cyclone (looking in the direction of motion), a direct hit occurs when the cyclone passes to within a distance equal to the radius of maximum wind of a cyclone. For locations on the right-hand side of the track, a direct hit occurs when the cyclone passes to within a distance equal to twice the radius of maximum wind. Compare indirect hit, strike. Source NOAA-NHC.

A type of weather radar that determines whether atmospheric motion is toward or away from the radar. Doppler radar determines the intensity of rainfall and uses the Doppler effect to measure the velocity of droplets in the atmosphere. Source: NOAA-NWS ERH.

The change in observed frequency of wave energy due to the relative motion of the observer and wave source. For example, as a train approaches your location, you hear a higher pitch sound. After the train has passed your location, you will hear a lower pitch sound. The Doppler radar uses this change in frequency to determine the velocity and direction of the wind. Source: NOAA-NWS SRH.

A column of generally cool air that rapidly sinks to the ground, usually accompanied by precipitation as in a shower or thunderstorm. Source: NOAA-NWS ERH.

(Also called parachute radiosonde.) A radiosonde with a parachute dropped from an airplane carrying receiving equipment for the purpose of obtaining an upper-air sounding during descent. Source: (c) 1999, American Meteorological Society. Used with permission.

Also known as a numerical weather prediction model, it is a computer program that uses a supercomputer to solve the mathematical equations governing the physics and motion of the atmosphere.