A comparison of the spectral energy and enstrophy budgets of blocking versus nonblocking periods

Data from the winters of 1978-79 and 1976-77 are analyzed in an attempt to identify any systematic differences in the time mean spectral energy and enstrophy budgets of blocking events in comparison with nonblocking periods. It is found that the most noteworthy differences between the spectral energy and enstrophy budgets of blocking versus nonblocking periods are in the nonlinear interaction terms. It is suggested that an explanation of the greater predictability of the Rex-type blocking found by Bengtsson (1981) might be found in the reversal of low wavenumber enstrophy cascade. This may indicate that the destruction of large-scale vorticity by down-scale cascade and eventual dissipation is greatly reduced or eliminated during blocking events. As a result, blocking patterns may be more persistent and therefore more predictable.