Difference between revisions of "Sigma-theta"
imported>Perlwikibot |
imported>Rbrandt |
||
(16 intermediate revisions by the same user not shown) | |||
Line 9: | Line 9: | ||
</div> | </div> | ||
− | <div class="definition"><div class="short_definition">( | + | <div class="definition"><div class="short_definition">(Used in [[physical oceanography]], symbol ''σ<sub>θ</sub>''.) The [[density]] ''ρ'' (<1000 kg m<sup>−3</sup>) that a [[parcel]] of water of [[salinity]] ''S'' and [[temperature]] ''T'' would have if it were raised [[adiabatic process|adiabatically]] to the sea surface, where its [[temperature]] would change from ''T'' to [[potential temperature]] ''θ'' due to [[adiabatic]] decompression. In symbols,</div><br/> <div class="paragraph"><div class="display-formula"><blockquote>[[File:sigma-theta-ocean.gif|link=|center|sigma-theta-ocean]]</blockquote></div></div><br/></div> |
− | </div> | + | |
+ | <div class="definition"><div class="short_definition">(Used in [[meteorology]], symbol ''σ<sub>θ</sub>''.) The [[standard deviation]] of horizontal [[wind direction]] used primarily in [[air pollution]] applications. Sigma-theta can either be computed directly from measured wind direction or with the Yamartino method (Yamartino 1984). Sigma-theta is used as a proxy to characterize the [[dispersion]] capabilities of the lower [[troposphere]] with different [[stability categories]]. The Yamartino method is given by:<br/> <div class="paragraph"><div class="display-formula"><blockquote>[[File:sigma-theta-atmos.gif|link=|center|sigma-theta-atmos]]</blockquote></div></div><br/></div> | ||
+ | |||
+ | <div class="definition"><div class="short_definition">where ''s<sub>a</sub>'' = (1/''n'')Σ<sub>''i''</sub>sin''θ<sub>i</sub>'' and ''c<sub>a</sub>'' = (1/''n'')Σ<sub>''i''</sub>cos''θ<sub>i</sub>'' are computed from a sequence of ''n'' wind angle (''θ<sub>i</sub>'') measurements.</div></div><br/> | ||
+ | |||
+ | <p>Yamartino, R. J., 1984: A comparison of several "single-pass" estimators of the standard deviation of wind direction. ''J. Climate Appl. Meteor.'', '''23''', 1362–1366, <nowiki>https://doi.org/10.1175/1520-0450(1984)023<1362:ACOSPE>2.0.CO;2</nowiki>.</p><br/> | ||
+ | |||
+ | <p>''Term edited 16 May 2018.''</p> | ||
{{TermIndex}} | {{TermIndex}} |
Latest revision as of 08:36, 22 June 2018
sigma-theta
Yamartino, R. J., 1984: A comparison of several "single-pass" estimators of the standard deviation of wind direction. J. Climate Appl. Meteor., 23, 1362–1366, https://doi.org/10.1175/1520-0450(1984)023<1362:ACOSPE>2.0.CO;2.
Term edited 16 May 2018.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.