Estimating the Bowen ratio over the open and ice‐covered ocean. Issue 9 (9th September 2013)

• Record Type: Journal Article
• Authors: Andreas, Edgar L; Jordan, Rachel E.; Mahrt, Larry; Vickers, Dean
• Is Part Of: Journal of geophysical research. Volume 118:Issue 9(2013:Sep.)
• Page Start: 4334
• Page End: 4345
• Publication Date: 2013-09-09
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/jgrc.20295
• Languages: English
• ISSNs: 2169-9275

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>[1] The Bowen ratio, the ratio of the turbulent surface fluxes of sensible (<italic>H<sub>s</sub></italic>) and latent (<italic>H<sub>L</sub></italic>) heat, <italic>Bo</italic> ≡ <italic>H<sub>s</sub></italic>/<italic>H<sub>L</sub></italic>, occurs throughout micrometeorology. It finds application in the Bowen ratio and energy budget method, where it provides both turbulent heat fluxes when only the available energy at the surface is known. It can yield an estimate of a missing <italic>H<sub>s</sub></italic> or <italic>H<sub>L</sub></italic> if the other flux is known. We also suggest that the Bowen ratio may provide the missing piece needed to infer the surface sensible heat flux from satellite data. For this study, we analyze almost 9000 eddy‐covariance measurements of <italic>H<sub>s</sub></italic> and <italic>H<sub>L</sub></italic>. About half were made over sea ice; the other half, over the open ocean. These are saturated surfaces where the surface specific humidity is the saturation value at the surface temperature. Surface temperatures ranged from −44°C to 32°C and predict the Bowen ratio through the Bowen ratio indicator, <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg4t8w5ccm" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:21699275:media:jgrc20295:jgrc20295-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>B</mml:mi><mml:msub><mml:mi>o</mml:mi><mml:mo>*</mml:mo></mml:msub><mml:mo>=</mml:mo><mml:msub><mml:mrow><mml:mrow><mml:mrow><mml:msub><mml:mi>c</mml:mi><mml:mi>p</mml:mi></mml:msub><mml:mo>/</mml:mo><mml:mrow><mml:mo stretchy="true">(</mml:mo><mml:mrow><mml:msub><mml:mi>L</mml:mi><mml:mi>v</mml:mi></mml:msub><mml:mo>∂</mml:mo><mml:msub><mml:mi>Q</mml:mi><mml:mrow><mml:mi>s</mml:mi><mml:mi>a</mml:mi><mml:mi>t</mml:mi></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:mo>∂</mml:mo><mml:mo>Θ</mml:mo></mml:mrow><mml:mo stretchy="true">)</mml:mo></mml:mrow></mml:mrow><mml:mo>|</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:msub><mml:mo>Θ</mml:mo><mml:mi>s</mml:mi></mml:msub></mml:mrow></mml:msub></mml:mrow></mml:math></alternatives>. Here <italic>c<sub>p</sub></italic> is the specific heat of air at constant pressure, <italic>L<sub>v</sub></italic> is the latent heat of sublimation or vaporization, and <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg4t8w5cht" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:21699275:media:jgrc20295:jgrc20295-math-0002" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>∂</mml:mo><mml:msub><mml:mi>Q</mml:mi><mml:mrow><mml:mi>s</mml:mi><mml:mi>a</mml:mi><mml:mi>t</mml:mi></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:mo>∂</mml:mo><mml:mo>Θ</mml:mo></mml:mrow></mml:math></alternatives> is the derivative of the saturation specific humidity (<italic>Q<sub>sat</sub></italic>) with temperature (Θ). All quantities are evaluated at the surface temperature, Θ<italic><sub>s</sub></italic>. Although <italic>H<sub>s</sub></italic> and <italic>H<sub>L</sub></italic> can occur in nine possible combinations, in our data set, three combinations represent over 90% of the cases: <italic>H<sub>s</sub></italic> > 0 and <italic>H<sub>L</sub></italic> > 0, <italic>H<sub>s</sub></italic> < 0 and <italic>H<sub>L</sub></italic> < 0, and <italic>H<sub>s</sub></italic> < 0 and <italic>H<sub>L</sub></italic> > 0. In each of these three cases, the data suggest <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg4t8w5cfq" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:21699275:media:jgrc20295:jgrc20295-math-0003" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>B</mml:mi><mml:mi>o</mml:mi><mml:mo>=</mml:mo><mml:mi>a</mml:mi><mml:mi>B</mml:mi><mml:msub><mml:mi>o</mml:mi><mml:mo>*</mml:mo></mml:msub></mml:mrow></mml:math></alternatives>, where <italic>a</italic> is 0.40, 3.27, and −0.65, respectively.</p> </abstract>