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Drought

Glossary

Being familiar with weather terminology will help you know what to expect when weather warnings are issued. The following terms are used frequently in reference to drought.

Agricultural drought - Refers to a situation where the amount of moisture in the soil no longer meets the needs of a particular crop.

Arid - Term used for an extemely dry climate. The degree to which a climate lacks effective, life-promoting moisture and agriculture is impracticable without irrigation.

Climate - The composite or generally prevailing weather conditions of a region, throughout the year, averaged over a series of years.

Climatology - The science that deals with the phenomena of climates or climatic conditions.

Crop Moisture Index - In 1968, Palmer developed the index to assess short-term crop water conditions and needs across major crop-producing regions. This index is a useful tool in forecasting short-term drought conditions.

Dog days - Name given to the very hot summer weather that may persists for four to six weeks between mid-July through early September in the United States. In western Europe, this period may exist from the first week in July to mid-August and is often the period of the greatest frequency of thunder. Named for Sirius, the Dog Star, which lies in conjunction with the sun during this period, it was once believed to intensify the sun's heat during the summer months.

Drought - A deficiency of moisture that results in adverse impacts on people, animals, or vegetation over a sizeable area.

Ground water - In hydrologic terms, water within the earth that supplies wells and springs; water in the zone of saturation where all openings in rocks and soil are filled, the upper surface of which forms the water table.

Hydrological drought - Occurs when surface and subsurface water supplies are below normal.

Hydrology - The scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water on or below the land surface.

Irrigation - In hydrologic terms, the controlled application of water to arable lands to supply water requirements not satisfied by rainfall.

Irrigation requirement - In hydrologic terms, the quantity of water, exclusive of precipitation, that is required for crop production. It includes surface evaporation and other economically unavoidable wastes.

Meteorological drought - A measure of departure of precipitation from normal. Due to climatic differences, what might be considered a drought in one location of the country may not be a drought in another location.

Palmer Drought Severity Index - (Abbrev. PDSI) - An index used to gage the severity of drought conditions by using a water balance equation to track water supply and demand. This index is calculated weekly by the National Weather Service.

Precipitation - Process where water vapor condenses in the atmosphere to form water droplets that fall to the Earth as rain, sleet, snow, hail, etc.

Socioeconomic drought - Refers to the situation that occurs when physical water shortages begin to affect people.

Soil moisture - Water contained in the upper part of the soil mantle. This moisture evaporates from the soil and is the used and transpired by vegetation.

Xeriscape™ - Quality landscaping that conserves water and protects the environment. The term Xeriscape (pronounced zera-scape) was coined in Colorado in 1981 in response to a prolonged drought. It derives from merging the Greek word "Xeros," meaning "dry," with the word "landscape."

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