Influence of short-term changes in solar activity on baric field perturbations in the stratosphere and troposphere

Influence of short-term changes in solar activity on baric (pressure) field perturbations is studied using such characteristics as the Sazonov index ( IS), describing the intensity of meridional transfer, the Blinova index (IB ), describing the intensity of zonal transfer, and 'vorticity area index' ( VAI) describing the tropospheric cyclonic perturbations, The epoch superpos ition method is used to reveal effects of the solar central meridian (CM) p assage of active regions, the Forbush decreases (FD) in galactic cosmic ray s, and the solar proton (SP) events. The results of the analysis show that influence of short-term changes in the solar activity on baric field pertur bations is the most evident in the stratosphere (30 mbar-level). The meridi onal circulation in case of the FD and SP events begin to increase about 5- 7 days before the key date, reaches maximum nearby the key date and decays after the key date. The meridional circulation in case of the solar CM pass age of active regions starts to increase after the key date and reaches the maximum by 5-6 days. Fluctuations of baric field within periods of 5-7 day s typical of meridional and zonal transfers in troposphere (500 mbar-level) are evidently connected with internal dynamics of the atmosphere, not with the effects of solar activity. VAI characterizing cyclonic activity in the troposphere, shows the striking correspondence to changes of the meridiona l circulation in the stratosphere. Comparison of changes in the stratospher ic perturbations with behavior of the UV irradiance in course of the FD and SP events show their full correspondence at the initial stage of these pro cesses. The conclusion is made that growth of baric perturbations observed in the stratosphere in associations with the FD and SP events before the ke y date is caused by the solar UV irradiance increase, whereas decay of the baric perturbations after the key date is related to direct influence of th e solar energetic corpuscular fluxes on the stratosphere, (C) 2000 Elsevier Science Ltd. All rights reserved.