Andrey A. Grachev

Bulk Parameterization of Air-Sea Fluxes: Updates and Verification for the COARE Algorithm

Abstract In 1996, version 2.5 of the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk algorithm was published, and it has become one of the most frequently used algorithms in the air–sea interaction community. This paper describes steps taken to improve the algorithm in several ways. The number of iterations to solve for stability has been shortened from 20 to 3, and adjustments have been made to the basic profile stability functions. The scalar transfer coefficients have been redefined in terms of the mixing ratio, which is the fundamentally conserved quantity, rather than the measured water vapor mass concentration. Both the velocity and scalar roughness lengths have been changed. For the velocity roughness, the original fixed value of the Charnock parameter has been replaced by one that increases with wind speeds of between 10 and 18 m s−1. The scalar roughness length parameterization has been simplified to fit both an early set of NOAA/Environmental Technology Laboratory (ETL) experiments and...

Upward Momentum Transfer in the Marine Boundary Layer

Abstract This paper focuses on the study of momentum flux between ocean and atmosphere in light winds and is based on the data collected during several field campaigns, the Atlantic Stratocumulus Transition Experiment, the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment, and the San Clemente Ocean Probing Experiment. Weak wind at sea is frequently accompanied by the presence of fast-traveling ocean swell, which dramatically affects momentum transfer. It is found that the mean momentum flux (uw covariance) decreases monotonically with decreasing wind speed, and reaches zero around a wind speed U ≈ 1.5–2 m s−1, which corresponds to wave age cp/U ≈ 10 for wave/swell conditions of the experiments in this study. Further decrease of the wind speed (i.e., increase of the wave age) leads to a sign reversal of the momentum flux, implying negative drag coefficient. Upward momentum transfer is associated with fast-traveling swell running in the same direction as the wind, and this regim...

Evaluations of the von Kármán constant in the atmospheric surface layer

The von Karman constant

The MATERHORN: Unraveling the Intricacies of Mountain Weather

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Parameterizing turbulent exchange over sea ice in winter

relates the flow speed profile in a wall-bounded shear flow to the stress at the surface. Recent laboratory studies in aerodynamically smooth flow report

Wind Stress Vector over Ocean Waves

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Review of wave‐turbulence interactions in the stable atmospheric boundary layer

values that cluster around 0.42–0.43 and around 0.37–0.39. Recent data from the atmospheric boundary layer, where the flow is usually aerodynamically rough, are similarly ambiguous:

Turbulent bulk transfer coefficients and ozone deposition velocity in the International Consortium for Atmospheric Research into Transport and Transformation

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A case study of the development of nocturnal slope flows in a wide open valley and associated air quality implications

is often reported to be significantly smaller than the canonical value 0.40, and two recent data sets suggest that

Structure of Turbulence in Katabatic Flows Below and Above the Wind-Speed Maximum

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