SHORT TIME VARIATIONS OF COSMIC RAYS INFLUENCE ON THE DURATION OF THE MACROSYNOPTICAL PROCESSES IN THE EARTH’S ATMOSPHERE I.V. Artamonova Saint-Petersburg State University, Saint-Petersburg, Russia

In this work we study variations of GCR flux on short time scales (which are known as Forbush decreases) and consider their influence on the duration of the macrosynoptical processes in the Earth’s atmosphere. GCR flux variations were chosen for consideration, since they seem to be one of the most important agents linking solar activity and the lower atmosphere.

These particles with energies from 100 MeV to several GeV are able to penetrate the stratosphere/upper troposphere heights and, on the other hand, their variations are closely related to solar activity.

Data used in the work Forbush Decreases Forbush Decreases – Using the data of Apatity Neutron Monitor (67°N, 33°E) we have selected 48 Forbush decreases with amplitude δN/N >2,5% not accompanying with the intensive solar proton fluxes (i.e., with the intensity I >100 proton·cm -2 ·s -1 ·sr -1 for particles with energy E >10 MeV during the ±3 days around the Forbush decrease onset). From the catalog of Vangengeim we selected 48 elementary sinoptic periods corresponding to these Forbush decreases. Solar Proton Events Solar Proton Events – During years we have selected 48 solar proton events with energy of particles Ep > 90 MeV. From the catalog of Vangengeim we selected 48 elementary sinoptic periods corresponding to these SPEs. Both Forbush decreases and solar proton events Both Forbush decreases and solar proton events were selected during the cold half of the year (October - March), because this period is characterized by sharpening of the ground temperature contrasts and, as a consequence, the maximum intensity of cyclonic activity in the North Atlantic region.

The definition of an elementary synoptic period was supposed by Russian meteorologist G.Ya. Vangengeim. According to Vangengeim, ESP is a period when the main characteristics of a particular synoptic situation remain constant over a large part of the globe. The mean duration of ESP is usually 3–5 days. Elementary synoptic periods are divided into 3 forms: 1. Eastern circulation form (E) 2. Meridional circulation form (C) 3. Zonal circulation form (W) The given classification is based on the similar geographic distribution of the fields of pressure and similar character of processes of their formation, direction of prevailing wind systems, similar character of main intrusions of air masses. Elementary synoptic periods

The given form of circulation is characterized by strengthening of moving of cyclones and anticyclones in the zonal flow from the West to the East. Temperature and pressure gradients between high and middle / low latitudes become to increase. Interzonal exchange of air masses weakens or stops. Black arrows correspond to trajectories of movement of cyclones, white arrows is to anticyclones’ trajectories. Zonal circulation form (W)

Eastern form of atmospheric circulation is characterized by development of stable waves of the big amplitude with the gradients directed along the latitude. There is a formation of high and warm anticyclones, mainly over the continents, which block west-east movement of air masses. Over Atlantic and Pacific oceans considerable zonal components remain exist. Interzonal exchange of air masses becomes more intensively. Black arrows correspond to trajectories of movement of cyclones, white arrows is to anticyclones’ trajectories. Eastern circulation form (E)

This form of circulation is characterized by intrusions of low cold Arctic anticyclones into the Europe through Scandinavia. High and warm anticyclone forms over East part of the Atlantic. It is observed a filling of the Icelandic minimum and weakening of cyclogenesis near Greenland. Interzonal exchange of air masses becomes more intensively. Black arrows correspond to trajectories of movement of cyclones, white arrows is to anticyclones’ trajectories. Meridional circulation form (C)

Duration of ESP during solar proton events Form C Form E Form W

Duration of ESP during Forbush dacreases Form C Form E Form W

Possible explanation of ESP duration variation during SPE North Atlantic cyclones intensification on the first days after energetic solar proton events leads to increase of the duration of the W form of ESP. Forbush decrease accompanying solar proton event leads to increase of the duration of the C form of ESP. Duration of the E form of ESP remains without considerable changes. Veretenenko and Thejll, JASTP, 2004

Possible explanation of ESP duration variation during FD Blocking anticyclones formation in the East Atlantic sector and over Scandinavia on the 3-4 th days after Forbush decreases of GCR leads to increase of the duration of the C form of ESP. Filling of the Icelandic minimum and weakening of cyclogenesis near Greenland and all over the Atlantic sector leads to decrease of the duration of the W and E forms of ESP. Veretenenko and Artamonova, JASTP, 2010

Possible mechanisms

Conclusions 1.Variation of the duration of elementary synoptic periods was carried out in the context of influence of solar proton events and Fofbush decreases of galactic cosmic rays on the baric system dynamic at high and middle latitudes. 2.An increase in the ESP duration for the zonal (W) and meridional (C) circulation forms and a reduction in the ESP duration for the eastern circulation form (E) were revealed on the days following the onsets of solar proton events. 3.During Forbush decreases of GCR an increase in the ESP duration for the meridional form C and a reduction in the ESP duration for the circulation forms W and E were detected. 4.It was shown that the detected changes in the ESP duration are caused by the influence of the variations of cosmic rays under study on the processes of evolution of North Atlantic cyclones and anticyclones resulting to the formation of stationary blocking baric systems over the East Atlantic and Europe in case of Forbush decreases of GCR and regeneration of cyclones near Greenland after solar proton events.