- Settore: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
The extent to which a statement is considered reliable. This is a subjective factor, as opposed to probability, which is a mathematical likelihood of occurrence, based on previous experience. For example, a forecaster may state that there is a 50% probability of rain, and assign a certainty factor of 95% to that statement. There are several methods of combining certainty factors to arrive at an overall certainty. The most common of these is the Dempster–Shafer rule (Shafer 1976).
Industry:Weather
The expected value of the product (x − ξ) (y − ζ), where ξ denotes the mean of x and ζ the mean of y. See correlation.
Industry:Weather
The emission of unburned fuel to the atmosphere from the crankcase of an internal combustion engine. Formerly a large source of hydrocarbons to the atmosphere, the rate of escape has been greatly reduced by recycling of the escaped gases to the cylinders by means of a device called the positive crankcase ventilation (PCV) valve. Crankcase ventilation contributes around 5% of unburned hydrocarbon emissions to the atmosphere.
Industry:Weather
The effect of exposing equipment to low temperatures for an extended period of time. Cold soak of engines necessitates preheating before their use, as lubricants have thickened, metal has become brittle, and tolerances have diminished.
Industry:Weather
The electrical current that is equivalent to the rate of charge transferred to the air from a pointed object (or array of objects) experiencing corona discharge. Ordinarily, the corona current from terrestrial objects at times of thunderstorm passage constitutes a transfer of negative charge from air to object. Compare point discharge current.
Industry:Weather
The elevation above mean sea level chosen as the reference datum level for all climatological records of atmospheric pressure in a given locality; not necessarily the same as station elevation. This term is denoted by the symbol Hpc in international usage. The reduction of pressure to this standard elevation is necessary only if a station has changed its specific location but has stayed within the general area, so that the two (or more) sets of records remain comparable.
Industry:Weather
The eastern boundary current of the North Pacific subtropical gyre. It flows southward along the coast of Washington and California and is associated with coastal upwelling during spring and summer (April–September). The associated low sea surface temperatures (about 15°C) produce a coastal strip of sea fog along the otherwise extremely hot coastline. In autumn and winter (October–March) the upwelling is replaced by northward flow known as the Davidson Current, which reaches its peak speed of 0. 2–0. 3 m s−1 in January.
Industry:Weather
The eastern boundary current of the North Atlantic subtropical gyre. It flows southward along the coast of Africa from Morocco to Senegal and is associated with coastal upwelling. The upwelling reaches its southernmost extent in winter (December–March) when the trade winds are strongest; it then extends past Cape Blanc (21°N), where the Canary Current separates from the African coast.
Industry:Weather
The downward flux of longwave radiation across a given surface, usually taken as the earth's surface. Counterradiation originates in emission by clouds and greenhouse gases at different heights and temperatures, and is modified by subsequent absorption before reaching the surface in question. The long-term global average of counterradiation reaching the earth's surface is about 330 W m−2, making it one of the largest terms in the surface energy balance.
Industry:Weather
The division of the earth's climates into a worldwide system of contiguous regions, each one of which is defined by relative homogeneity of the climatic elements. The earliest known classification of climate, devised by the Greeks, simply divided each hemisphere into a mathematical climate of three zones, the “summerless,” “intermediate,” and “winterless,” thus accounting only for the latitudinal differences in solar effect (the Greek word klima means “inclination”). More recently, these zones have been labeled the Torrid, Temperate, and Frigid Zones. Apparently, the first major improvement over this classification was introduced by Alexander Supan in the nineteenth century. He based his zones on actual rather than theoretical temperatures, and named one hot belt, two temperate belts, and two cold caps. Supan also divided the world into 34 climatic provinces, with no attempt to relate similar climates of different locations. Another basic and much used approach recognizes other climatic controls as well as the sun. The resulting climates are called (with variations) polar, temperate, tropical, continental, marine, mountain, and probably others. Of the major climatic classifications in use today, those of W. Köppen (1918) and C. W. Thornthwaite (1931) are referred to most often. Köppen's elaborate “geographical system of climates” is based upon annual and seasonal temperature and precipitation values; his climatic regions are given a letter code designation. The major categories are tropical rainy climate, dry climate, temperate rainy climate, snow forest climate, tundra climate, and perpetual frost climate. Gorczyński (1948) devised a decimal number system similar to the Köppen classification. Thornthwaite's (1931) bioclimatological system utilizes indices of precipitation effectiveness to outline humidity provinces, and thermal efficiency for temperature provinces; and again, a letter code designates regions. Thornthwaite (1948) introduced an approach to a “rational” classification, wherein potential evapotranspiration is used as a measure of thermal efficiency, and is compared to precipitation to form a moisture index and to show amounts and periods of water surplus and deficiency. Definite break points are revealed that are adaptable as climatic boundaries. Many authors have devised modified classifications to instruct a particular audience. An excellent example is that of C. E. P. Brooks (1951) in which climatic regions are defined with respect to human activity.
Industry:Weather
