The protection of human lives and assets from natural disasters or environmental change is the main purpose of meteorological services. In order to take appropriate measures, is most important to detect signs of hazardous phenomena.
Detection depends on the nature of the phenomena and their scales in time and space.
Large-scale clouds associated with typhoons or frontal systems are successfully revealed by the meteorological satellite imageries. It is, however, rather difficult to know precisely the area and amount of a given precipitation. The help of the radar and rain gauge networks is required in measurement. Such small-scale phenomena as tornadoes,gust winds, thunderstorms, hails, and dense fogs are hard to investigate with the traditional meteorological observing facilities. But they directly affect air and surface transportations.