| contributor author | McMillan, Justine M.;Hay, Alex E. | |
| date accessioned | 2018-01-03T11:03:38Z | |
| date available | 2018-01-03T11:03:38Z | |
| date copyright | 10/27/2016 12:00:00 AM | |
| date issued | 2016 | |
| identifier other | jtech-d-16-0131.1.pdf | |
| identifier uri | http://138.201.223.254:8080/yetl1/handle/yetl/4246736 | |
| description abstract | AbstractSpectral and structure function methods are implemented to compute the dissipation rate ε from broadband, diverging-beam acoustic Doppler current profiler (ADCP) data collected at four sites in a high-flow tidal channel. This paper shows that middepth estimates of ε obtained from spectral and second-order structure function (SF2) methods are both lognormally distributed with comparable means and variances. Speed bin?averaged ε values agree to within 16%, depending on the site and tidal phase (ebb/flood). The close agreement between the two independent methods provides further support for the argument put forward by McMillan et al.: that is, that the factor-of-2 difference between shear probe and (spectral) ADCP estimates of ε was likely caused by spatial differences in turbulence levels. The agreement between the spectral and both second- and third-order structure function methods also supports the use of for the SF2 universal constant. Notably, however, the SF3 method was less robust for these data. Two additional aspects of the SF2 approach are examined in some detail: 1) the differences from upstream- and downstream-facing beams are shown to arise from the Reynolds stress and 2) the inability of the ADCP to resolve small-scale motions does not affect the estimates of ε but yields apparent Doppler noise levels that?counterintuitively?decrease with increasing flow speed and increasing dissipation rate. A modified SF2 method that accounts for the variance associated with the unresolved scales removes the flow speed dependence and yields noise level estimates that agree with the spectral values. | |
| publisher | American Meteorological Society | |
| type | Journal Paper | |
| journal volume | 34 | |
| journal issue | 1 | |
| journal title | Journal of Atmospheric and Oceanic Technology | |
| identifier doi | 10.1175/JTECH-D-16-0131.1 | |
| journal fristpage | 5 | |
| journal lastpage | 20 | |
| tree | Journal of Atmospheric and Oceanic Technology:;2016:;volume( 034 ):;issue: 001 | |
| contenttype | Fulltext | |