Intercomparison of Bulk Aerodynamic Algorithms for the Computation of Sea Surface Fluxes Using TOGA COARE and TAO Data

Abstract

A bulk aerodynamic algorithm is developed for all stability conditions for the computation of ocean surface fluxes. It provides roughness lengths of wind, humidity, and temperature for a wind speed range from 0 to 18 ms 21: zo 5 0.013 /g 1 0.11n/u * and ln(zo/zot) 5 ln(zo/zoq) 5 2.67 2 2.57 as derived using the Tropical 2 1/4 u Re ** Oceans Global Atmosphere (TOGA) Coupled Ocean‐Atmosphere Response Experiment (COARE) data constrained by other observations under high wind conditions. Using the TOGA COARE ship data and the multiyear hourly TOGA Tropical Atmosphere‐Ocean moored buoy data, intercomparison of six different algorithms, which are widely used in research, operational forecasting, and data reanalysis, shows that algorithms differ significantly in heat and momentum fluxes under both very weak and very strong wind conditions, but agree with each other under moderate wind conditions. Algorithms agree better for wind stress than for heat fluxes. Based on past observations, probable deficiencies in roughness lengths (or neutral exchange coefficients) of some of the algorithms are identified along with possible solutions, and significant issues (particularly the trend of the neutral exchange coefficient for heat with wind speed under strong wind conditions) are raised for future experiments. The vapor pressure reduction of 2% over saline seawater has a significant impact on the computation of surface latent heat flux under strong wind conditions and should be considered in any bulk aerodynamic algorithm.