Impacts of evolving low-level jets on turbulence structures in the stable surface layer

This study reports a case study of nocturnal surface fluxes made at a flat and homogeneous site in the presence of low-level jets (LLJs). Specifically, it documents the temporal evolution of the overlying jet and the coincident response of surface fluxes. The present study highlights several factors linking the evolution of low-level jets to surface fluxes: 1) wavelet analysis shows that turbulent fluxes have longer time scales similar with temporal scale of LLJ evolution; 2) turbulent mixing is enhanced during the transition period of low-level jets; and 3) CO₂, water vapor and heat show dissimilarity from momentum. We also found that LLJ activity is closely related not only to turbulent motions but also to the divergence of mean flow. An examination of scalar profiles and turbulence data reveal that a LLJ transports CO₂ and water vapor by advection.