The near-neutral marine atmospheric boundary layer with no surface shearing shress: a case study

Abstract

Data from a marine coastal experiment over the Baltic Sea, comprising air-borne measurements and mast measurements, have been used to highlight the turbulence dynamics of a case with most unusual flow characteristics. The boundary layer had a depth of about 1200m. The thermal stratification was near neutral, with small positive heat flux below 300m and equally small negative heat flux above. The entire situation lasted about 6 hours. Turbulence levels were unexpectedly high in view of the fact that momentum flux was negligible (in fact positive) in the layers near the surface, and buoyancy flux was also small. The turbulence was found to scale with the height of the boundary layer, giving rise to velocity spectra having the shape of those characteristic of convectively mixed boundary layers. -Authors