Moisture index: Difference between revisions
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#<div class="definition"><div class="short_definition">That portion of total [[precipitation]] used to satisfy plant (vegetation) needs.</div><br/> </div> | #<div class="definition"><div class="short_definition">That portion of total [[precipitation]] used to satisfy plant (vegetation) needs.</div><br/> </div> | ||
#<div class="definition"><div class="short_definition">As used by C. W. Thornthwaite in his 1948 [[climatic classification]]: an overall measure of [[precipitation effectiveness]] for plant growth that takes into consideration the weighted influence of [[water surplus]] and water deficiency as related to [[water need]] and as they vary according to [[season]]. For a given [[station]], it is calculated by the formula <div class="display-formula"><blockquote>[[File:ams2001glos-Me20.gif|link=|center|ams2001glos-Me20]]</blockquote></div> which becomes <div class="display-formula"><blockquote>[[File:ams2001glos-Me21.gif|link=|center|ams2001glos-Me21]]</blockquote></div> where ''I''<sub>''m''</sub> is the moisture index, ''s'' the water surplus, ''d'' the water deficiency, and ''n'' the water need. The calculation of ''s'' and ''d'' is made on a normal month-to-month basis, with ''s'' being the total surplus from all months having a water surplus, and ''d'' the total of all monthly deficiencies; each is represented by the difference between monthly [[precipitation]] and monthly [[potential evapotranspiration]] (in centimeters or inches). Here ''n'' is the annual potential evapotranspiration.</div><br/> <div class="paragraph">The moisture index replaced Thornthwaite's previously used (1931) [[precipitation-effectiveness index]]. <br/>''Compare'' [[Palmer Drought Severity Index]].</div><br/> </div><div class="reference">Thornthwaite, C. W. 1948. An approach toward a rational classification of climate. Geographical Review. 38. 55–94. </div><br/> <div class="reference">Thornthwaite, C. W. 1931. Climates of North America according to a new classification. Geographical Review. 21. 633–655. </div><br/> | #<div class="definition"><div class="short_definition">As used by C. W. Thornthwaite in his 1948 [[climatic classification]]: an overall measure of [[precipitation effectiveness]] for plant growth that takes into consideration the weighted influence of [[water surplus]] and water deficiency as related to [[water need]] and as they vary according to [[season]]. For a given [[station]], it is calculated by the formula <div class="display-formula"><blockquote>[[File:ams2001glos-Me20.gif|link=|center|ams2001glos-Me20]]</blockquote></div> which becomes <div class="display-formula"><blockquote>[[File:ams2001glos-Me21.gif|link=|center|ams2001glos-Me21]]</blockquote></div> where ''I''<sub>''m''</sub> is the moisture index, ''s'' the water surplus, ''d'' the water deficiency, and ''n'' the water need. The calculation of ''s'' and ''d'' is made on a normal month-to-month basis, with ''s'' being the total surplus from all months having a water surplus, and ''d'' the total of all monthly deficiencies; each is represented by the difference between monthly [[precipitation]] and monthly [[potential evapotranspiration]] (in centimeters or inches). Here ''n'' is the annual potential evapotranspiration.</div><br/> <div class="paragraph">The moisture index replaced Thornthwaite's previously used (1931) [[precipitation-effectiveness index|precipitation-effectiveness index]]. <br/>''Compare'' [[Palmer Drought Severity Index]].</div><br/> </div><div class="reference">Thornthwaite, C. W. 1948. An approach toward a rational classification of climate. Geographical Review. 38. 55–94. </div><br/> <div class="reference">Thornthwaite, C. W. 1931. Climates of North America according to a new classification. Geographical Review. 21. 633–655. </div><br/> | ||
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Latest revision as of 16:27, 25 April 2012
moisture index
- That portion of total precipitation used to satisfy plant (vegetation) needs.
- As used by C. W. Thornthwaite in his 1948 climatic classification: an overall measure of precipitation effectiveness for plant growth that takes into consideration the weighted influence of water surplus and water deficiency as related to water need and as they vary according to season. For a given station, it is calculated by the formulawhich becomes
where Im is the moisture index, s the water surplus, d the water deficiency, and n the water need. The calculation of s and d is made on a normal month-to-month basis, with s being the total surplus from all months having a water surplus, and d the total of all monthly deficiencies; each is represented by the difference between monthly precipitation and monthly potential evapotranspiration (in centimeters or inches). Here n is the annual potential evapotranspiration.
The moisture index replaced Thornthwaite's previously used (1931) precipitation-effectiveness index.
Compare Palmer Drought Severity Index.
Thornthwaite, C. W. 1948. An approach toward a rational classification of climate. Geographical Review. 38. 55–94.
Thornthwaite, C. W. 1931. Climates of North America according to a new classification. Geographical Review. 21. 633–655.
