figures i - uploaded by Ben I. Moat
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n brackets indicate the maximum rate of change of velocity per cell (expressed as a percentage of the free stream velocity) for each site.
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Wissenschaftler des Thünen-Instituts für Holzforschung in Hamburg untersuchten eine berühmte, fast 400 Jahre alte Harfe mit neu entwickelten, zerstörungsfreien Methoden der Holzartenidentifizerung. Die Untersuchung ist Teil eines groß angelegten, interdisziplinären Forschungsprojektes mit dem Ziel einer Rekonstruktion dieses einzigartigen Instrumen...
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... Experience has indicated that mean streamwise flow tilts greater than about 15 • give questionable fluxes. Furthermore, these observed flow tilt angles are significantly greater than the 2.3 • flow tilt angle for bow-on winds obtained from model flow-distortion studies of the RV Knorr (Moat and Yelland 1998;Yelland et al. 2002), suggesting that the true flow distortion may be greater than the modelled one. Therefore, we have estimated that the mean wind speed at the sonic anemometer location is decreased by about 4.5% rather than the 0.85% estimated by the modelling studies. ...
... The FASTEX C Dn10 values from the ID technique are in good agreement with those from the ID technique of numerous other studies. The shaded area in Fig. 8(a) encompasses the ID curves from Large and Pond (1982), Anderson (1993), Yelland et al. (1998) and . It also encompasses the curves obtained from the buoy-based covariance measurements of Smith (1980), Large and Pond (1982) and , the first two studies using the Bedford Institute buoy 10 km off the coast of Novia Scotia and the last study using the ASIS (Air-Sea Interaction Spar) buoy 50 km from shore in the small, semi-circular Gulf of Lyon. ...
Mid-Atlantic measurements from the research vessel (RV) Knorr during the Fronts and Atlantic Storm-Tracks Experiment (FASTEX) are presented, and then used to examine the near-surface environment and air-sea interaction processes during the passage of ten frontal systems. This dataset includes measurements of the surface momentum, sensible-heat and moisture fluxes obtained from three different methods. The inertial dissipation (ID) drag coefficients from the RV Knorr are consistent with the ID data from other measurements in open-ocean storm environments. The covariance drag coefficients are generally larger than the ID values, indicating either the presence of flow distortion problems in the covariance data or a failure of the assumptions inherent to the ID technique at these higher wind speeds. Estimates of the wind speed dependence of the momentum, sensible-heat and latent-heat transfer coefficients are based on averaged values from the two methods. These measurements: (i) contribute significantly to the limited set of surface flux measurements for 10 m neutral winds in the 15-21 m s(-1) range; (ii) contain the only ship-based covariance flux measurements successfully obtained in an open-ocean, high wind speed, storm environment; and (iii) include coincident wave-height measurements. The relationships between the surface layer and the synoptic atmospheric environment is examined using composites of atmospheric and oceanic surface-layer characteristics computed in ten storms for which the RV Knorr passed through the open-wave warm sector and the cold front. These composites show minima in the sensible-and latent-heat fluxes, and a maximum in the momentum flux, just before the frontal passage during the warm-sector peak in wind speed. A second momentum flux maximum of comparable magnitude occurs in the middle of the post-frontal regime. Though the warm-sector sensible-heat flux minimum is slightly negative, the sum of the two heat fluxes is positive, suggesting a positive impact on the synoptic development of these storms. Wave heights increase steadily from the eastern half of the warm sector to the frontal passage, remaining high through most of the post-frontal regime before decreasing. Differences between covariance and ID stresses are largest during the times bracketing the cold front when the wave heights and stresses are large. Differences between covariance and bulk stresses are greatest in the pre-frontal low-level jet, when the frequency of waves with periods of 6-9 s maximizes, and in the post-frontal regime where the wind direction veers. Systematic differences between stress direction and wind direction are observed.
Mid-Atlantic measurements from the research vessel (RV) Knorr during the Fronts and Atlantic Storm-Tracks Experiment (FASTEX) are presented, and then used to examine the near-surface environment and air–sea interaction processes during the passage of ten frontal systems. This dataset includes measurements of the surface momentum, sensible-heat and moisture fluxes obtained from three different methods. The inertial dissipation (ID) drag coefficients from the RV Knorr are consistent with the ID data from other measurements in open-ocean storm environments. The covariance drag coefficients are generally larger than the ID values, indicating either the presence of flow distortion problems in the covariance data or a failure of the assumptions inherent to the ID technique at these higher wind speeds. Estimates of the wind speed dependence of the momentum, sensible-heat and latent-heat transfer coefficients are based on averaged values from the two methods. These measurements: (i) contribute significantly to the limited set of surface flux measurements for 10 m neutral winds in the 15–21 m s⁻¹ range; (ii) contain the only ship-based covariance flux measurements successfully obtained in an open-ocean, high wind speed, storm environment; and (iii) include coincident wave-height measurements.
