Variations of the Turbulent Fluxes of Momentum, Heat and Moisture over Lake Ontario

McBean, Gordon; Paterson, Rod

doi:10.1175/1520-0485(1975)005<0523:vottfo>2.0.co;2

Cited by 18 publications

(4 citation statements)

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“…It has been reported that drag coefficients from aircraft measurements tend to be greater than surface-derived measurements [Greenhut, 1981;Nicholls and Readings, 1979;McBean and Paterson, 1975] and that areal measurements over ice should be greater than single floe estimates [Arya, 1975]. That the apparent surface roughness observed visually was greater in Macklin's [1983] marginal ice zone case than in the present case is consistent with both studies, having comparable values of momentum drag coefficients.…”

Section: Discussionsupporting

confidence: 87%

Air‐ice drag coefficients for first‐year sea ice derived from aircraft measurements

Walter¹,

Gilmer²

1984

J. Geophys. Res.

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Turbulent flux measurements were made at four levels (42, 90, 195, and 340 m) by the NOAA P-3 aircraft over first-year sea ice in the northern Bering Sea during February 1982. Three profiles of momentum flux and mean wind were used to calculate an air-ice drag coefficient CD of 3.0 ___ .6 x 10 -3 referenced to a 10-m anemometer height. The boundary layer was slightly unstable (z.JL = -1.2, where z i was the inversion height of 660 m and L the Monin-Obukhov length). The mean wind speed at the 42-m height was 17 m/s, and the air temperature was -20øC. From turbulent heat flux measurements the value of the bulk heat transfer coefficient Ctt was 0.73 .+_ .16 x 10 -3, giving a C•/C• of 0.24. The Bowen ratio was greater than 2.8. Comparison of the present turbulent flux and variance profiles with those collected over the ocean shows agreement, which increases confidence in the calculations. The geostrophic drag coefficient lu.I/IGI, where u. is the friction velocity and G is the geostrophic wind, was 0.047. The turning angle of the surface wind (measured by an anemometer at a height of 3 m on the ice) was 32 ø, and the ratio of surface wind speed to the geostrophic wind speed was 0.76.

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Section: Discussionsupporting

confidence: 87%

Air‐ice drag coefficients for first‐year sea ice derived from aircraft measurements

Walter¹,

Gilmer²

1984

J. Geophys. Res.

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“…Durand et al, 1987). Aircraft-based eddy correlation flux measurements have been made -apart from momentum and sensible heatof ozone (Lenschow et al, 1981 and, water vapor (Grossmann and Bean, 1973;McBean and Peterson, 1975;Bean et al 1976;Hacker, 1982;Desjardins et al, 1989) and CO* (Desjardins et al, 1982 andAlvo ef al., 1984;Austin et al, 1987). Fast response sensors are being developed to apply the technique to other trace gases, such as methane, and the use of such techniques is likely to grow due to their versatility of application, particularly in the interpretation of satellite observations at remote sites.…”

Section: Introductionmentioning

confidence: 99%

Footprint prediction of scalar fluxes from analytical solutions of the diffusion equation

Schuepp

Leclerc

MacPherson

et al. 1990

Boundary-Layer Meteorol

750

399

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The use of analytical solutions of the diffusion equation for 'footprint prediction' is explored. Quantitative information about the 'footprint', i.e., the upwind area most likely to affect a downwind flux measurement at a given height z, is essential when flux measurements from different platforms, particularly airborne ones, are compared. Analytical predictions are evaluated against numerical Lagrangian trajectory simulations which are detailed in a companion paper (Leclerc and Thurtell, 1990). For neutral stability, the structurally simple solutions proposed by Gash (1986) are shown to be capable of satisfactory approximation to numerical simulations over a wide range of heights, zero displacements and roughness lengths. Until more sophisticated practical solutions become available, it is suggested that apparent limitations in the validity of some assumptions underlying the Gash solutions for the case of very large surface roughness (forests) and tentative application of the solutions to cases of small thermal instability be dealt with by semi-empirical adjustment of the ratio of horizontal wind to friction velocity. An upper limit of validity of these solutions for z has yet to be established.

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“…It has been reported that, in general, drag coefficients from aircraft measurements made by hying crosswind tracks tend to be larger than surface-derived measurements (Greenhut, I98 I ;Nicholls and Readings, 1979;McBean and Paterson, 1975) due to differences in how the momentum-transporting eddies are sampled in each case. The results in Table V are consistent with previous aircraft drag measurements, both over sea ice and the marginal ice zone (Walter et al, 1984;Overland, 1985).…”

Section: Bulk Transfer Coefficientsmentioning

confidence: 99%

A study of the planetary boundary layer over the polynya downwind of St. Lawrence Island in the Bering Sea using aircraft data

Walter

1989

Boundary-Layer Meteorol

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Turbulence data collected with the gust probe system on the NOAA P-3 aircraft over the polynya downwind of St. Lawrence Island in the Bering Sea are used to study the fluxes of heat, momentum, and moisture from the polynya. The data also allow study of the effect of the topography of St. Lawrence Island on the atmospheric boundary-layer flow over the polynya and ultimately on ice production in the polynya. Two cases are studied: one (Feb. IS, 19X2) where the topographic effects are minimal and the other (Feb. 18, 1983) where the topographic effects are dominant. Calculation of the surface drag coefficient, Co, for the Feb. IS, 1982 case over young greylwhite ice gave a value of I .2 x I O-s, which is in close agreement with previous results. The value of the drag coefficient for the greylwhite ice regime on Feb. 18, 1983, where the upstream topography on St. Lawrence Island had an important influence on the flow over the polynya, was 3.2 x IO-'. It was determined that this higher value was related to the more efficient mixing of momentum downward by turbulent eddies generated by flow over and around the topography. The area-averaged heat transfer coefficient, C,, over the polynya was on the order of I. I x lttw3 for both days, but there were large variations in heat flux across the polynya due to variations in the flow caused by the topography. Conditional sampling techniques applied to the turbulence data showed that the fractional areas occupied by updrafts and downdrafts were 28% and 36%, respectively, and that these results were within the range of values found in previous studies for over-land and over-ocean conditions.

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Variations of the Turbulent Fluxes of Momentum, Heat and Moisture over Lake Ontario

Cited by 18 publications

References 0 publications

Air‐ice drag coefficients for first‐year sea ice derived from aircraft measurements

Air‐ice drag coefficients for first‐year sea ice derived from aircraft measurements

Footprint prediction of scalar fluxes from analytical solutions of the diffusion equation

A study of the planetary boundary layer over the polynya downwind of St. Lawrence Island in the Bering Sea using aircraft data

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