A simplified or generalized representation of reality; a description, analogy, picture, or hypothesis to help visualize something that cannot be directly observed.

A model that is a diagram or description of a set of relationships between factors that describe how a system works, such as an ecological model.

In a psychrometer, the thermometer with its bulb covered with a jacket of clean muslin which is saturated with distilled water before an observation.

General name for instruments designed to determine the moisture content of air. A psychrometer consists of dry- and wet-bulb thermometers that give the dry- and wet-bulb temperatures, which in turn are used to determine relative humidity and dew point.

Transfer of heat in straight lines through a gas or vacuum other than by heating of the intervening space.

Documentation Unit staff maintain incident files and data for legal, analytical, and historical purposes, including a complete record of the major steps taken to resolve the incident. They also provide duplication services for incident personnel; compile, reproduce, and distribute the IAP; and maintain the files and records that are developed as part of the IAP and planning function.

Geographical position determined by visual reference to the surface, by reference to one or more radio navigational aids, by celestial plotting, or by any other navigational device.

Wind blowing from land to water.

A device that adds a predetermined amount of foam concentrate to water to form foam solution.

That portion of the fire with slower rates of fire spread and lower intensity normally moving into the wind and/or down slope.