Hyun-Mi Oh

Evaluation of Boundary Layer Similarity Theory for Stable Conditions in CASES-99

Abstract The Monin–Obukhov similarity theory and a generalized formulation of the mixing length for the stable boundary layer are evaluated using the Cooperative Atmosphere–Surface Exchange Study-1999 (CASES-99) data. The large-scale wind forcing is classified into weak, intermediate, and strong winds. Although the stability parameter, z/L, is inversely dependent on the mean wind speed, the speed of the large-scale flow includes independent influences on the flux–gradient relationship. The dimensionless mean wind shear is found to obey existing stability functions when z/L is less than unity, particularly for the strong and intermediate wind classes. For weak mean winds and/or strong stability (z/L > 1), this similarity theory breaks down. Deviations from similarity theory are examined in terms of intermittency. A case study of a weak-wind night indicates important modulation of the turbulence flux by mesoscale motions of unknown origin.

Quality Control and Tilt Correction Effects on the Turbulent Fluxes Observed at an Ocean Platform

This study investigates atmospheric factors influencing the quality and the postprocessing (e.g., tilt correction) of fast-response measurements of turbulent fluxes for difficult open-sea measurements over an offshore platform. The data were collected at the Ieodo Ocean Research Station over the Yellow Sea during the periodfrom 5 November 2007 to19 February2008.The qualitycontrol removalof the data generallydepends on wind speed, relative humidity, significant wave height, visibility, and stability. The removal of substantial water vapor data with weak-wind stable conditions is investigated. Three different tilt correction algorithms (double rotation, triple rotation, and planar fit) are applied to correct the data because of inadvertent tilt of sonic anemometers. The choice of tilt correction method significantly influences the angle between the wind and stress direction.