The role of deformation and other quantities in an equation for enstrophy as applied to atmospheric blocking

•New equations for enstrophy and enstrophy advection are derived.•Enstrophy has geopotential, vorticity, zonal wind, and deformation terms.•Enstrophy advection has ageostrophic relative vorticity and deformation terms.•A blocking event is examined using the enstrophy equation.

In this note, equations for enstrophy and enstrophy advection are derived in terms of well-known quantities, assuming horizontal frictionless flow on a beta-plane. Specifically, enstrophy can be written in terms of the geopotential (or pressure), relative vorticity, zonal wind, and resultant deformation. Enstrophy advection is shown to be related to the time evolution of deformation and ageostrophic relative vorticity. Based on previous research, these terms may contribute to instability associated with atmospheric blocking development and decay.