On Turbulent Helicity in the Surface Layer of the Atmosphere

Abstract

Synchronous measurements of vorticity and velocity in the boundary layer of the atmosphere were carried out using the original three-component acoustic circulator developed at the Obukhov Institute of Physical Physics (IAP) in 2019–2020. The measurements were carried out in summer at the Tsimlyansk scientific station (in 2021 and 2022) at heights of 1.75 and 30 m. For different realizations, turbulent helicity has negative values on average, which is possibly due to the presence of local (breeze) winds. The spectra of turbulent helicity exhibit a slope close to –5/3, which corresponds to the transfer of helicity along the spectrum towards small scales (direct cascade). Spectrum slopes of –4/3 are also observed, as well as, in the low-frequency region, –1, associated with the convective component, wind shear, and submesoscale structures. The components of the turbulent vortex flow are calculated. The helicity values agree with the previously measured and theoretical estimates obtained for neutral conditions.