| Section A | A index | 281-289 of 917 terms |
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agonic line—The line through all points on the earth's surface at which the magnetic declination is zero; that is, the locus of all points at which magnetic north and true north coincide. This line is a particular case of an isogonic line. The position of this line exhibits variations in time, but in 1995 was so located that it emanated from the north magnetic pole, trended southward through the Great Lakes region, left the American mainland near Mississippi, cut across South America to near Buenos Aires, thence through the south magnetic pole, and up in an irregular path on the other side of the earth to return to the north magnetic pole. At the present time, the North American segment of the agonic line is drifting very slowly westward. Compare aclinic line.
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agricultural climatology—In general, climatology as applied to the effect of climate on crops. It includes especially the length of the growing season, the relation of growth rate and crop yields to the various climatic factors and hence the optimal and limiting climates for any given crop, the value of irrigation, and the effect of climatic and weather conditions on the development and spread of crop diseases. This discipline is primarily concerned with the space occupied by crops, namely, the soil and the layer of air up to the tops of the plants, in which conditions are governed largely by the microclimate.
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agricultural meteorological station—A collection of sensors connected to a data logger, designed to accumulate several types of soil and atmosphere observations, and report weather variables related to agriculture, representing conditions for a designated area.
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agricultural meteorology—In general, meteorology and micrometeorology as applied to specific agricultural systems and of agriculture as applied to specific atmospheric conditions. This discipline may emphasize atmospheric transport of insects, pathogens, etc., that impact agriculture as well as energy and mass exchange of plants and animals with the atmospheric environment. The effect of soils and vegetation on the ratio of sensible and latent energy exchange is representative of the impact of agriculture on meteorology.
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agrometeorological forecasting—The prediction of certain weather conditions or patterns that may have a significant effect on agriculture.
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