Global electric circuit modulation of winter cyclone vorticity in the northern high latitudes

Small changes in extended winter (November-March) 500 hPa vorticity area index (VAI) values for the 60-80°N latitude band are shown to be positively correlated with changes in a proxy for the high latitude ionosphere-to-surface current density ^Jz . The proxy was obtained from low latitude ^Jz values, measured at Mauna Loa Observatory (MLO) during the years 1960-1961 and 1977-1982, which were taken as proportional to the global ionospheric potential ^Vi . Such MLO ^Jz values may also serve as proxies for high latitude ^Jz , provided that they are not used during Forbush decreases or during periods of high stratospheric aerosol loading. The MLO data were of sufficient quantity and quality to obtain high latitude ^Jz proxies for five northern hemisphere winters. These proxies were used in linear regressions with lagged values of anomalies in the VAI (with lags extending from -150 to +150 days). For the regression analysis using VAI values from the four 1977-1982 winters, the largest ^R2 value occurred for a lag of +2 days, and the corresponding regression coefficient was the second largest in magnitude for the 301 day interval. An ANOVA test showed this result to have a statistical significance of greater than 95%. For the regression analysis using data from only the 1960-1961 winter, both the maximum slope and ^R2 value occurred for a lag of -3 days. However, the autocorrelation of the VAI has a width of ∼15 days, and the noise associated with the small number of data points for 1960-1961 suggests that the maxima were displaced to negative lags by noise. The overall results are consistent with Tinsley's hypothesis that higher ^Jz values enhance the vorticities of relatively intense winter cyclones when latent heat is important for their development. Electric charge deposited in clouds by ^Jz modulates the scavenging rates for both cloud condensation nuclei and ice-forming nuclei. The hypothesis is that these modulate the updraft vigor by the Rosenfeld mechanism, thus increasing the cyclonic vorticity.