The vorticity budget of an individual atmospheric vortex for the Hawaiian High

The analysis of vortex structures in the atmosphere can be performed using various approaches. One of these approaches is based on the analysis of the decomposition of vorticity fields into empirical orthogonal functions (EOFs). We consider an atmospheric vortex that exists quasi-permanently in a certain region (the Hawaiian anticyclone was chosen as the study object). It is proposed to consider evolution of an individual atmospheric vortex based on the vorticity budget equation known from dynamic meteorology (Kislov et al., 2017). The spatial structure analysis of the vorticity field of the Hawaiian anticyclone showed that the first mode of EOF decomposition describes more than 50% of the total variability. This allows us to consider the equation only for the principal component (PC) in the first EOF mode. The study of the equation components describing the vorticity dynamics allows to estimate more and less significant processes for vortex evolution. It was shown that the evolution of vorticity in a subtropical anticyclone is significantly affected by horizontal layer-average temperature advection, which may be due to a significant temperature gradient between low and high latitudes. Vertical movements and vorticity advection at upper troposphere can also be a significant factor in the evolution of a subtropical anticyclone. The sensible heat flux and the radiation balance have a less significant effect on the vortex dynamics, and the role of the latent heat flux is minimal. The vorticity balance equation was tested using ERA5 reanalysis data (Hersbach et al., 2018). This leads to the appearance of a discrepancy in the equation, due to the underestimation of a number of factors and the imperfection of the reanalysis data. The resulting discrepancy was approximated by regression through the first EOF mode PC and the white noise term.

The study was supported by grant of Moscow State University (121051400081-7).