Abstract:
The Sun is the main source of energy for all Earth’s geosystems, including climate, weather, mean sea level, winds, precipitation, and etc., mainly through Total Solar Irradiance (TSI), whose variations during solar activity cause various changes on the Earth surface. Climate processes, interactions between atmosphere-and ocean system, various local, regional and global hydrological cycles are the main mediator between solar activity and a number of geophysical processes on the Earth surface. The temperature at the Earth surface is widely used climate index, whose variations consist of significant seasonal oscillations, trend and long-term cycles. The variations of temperature over Bulgaria is investigated by means of several long time series of meteorological observations. The changes of seasonal components of temperature and long-term oscillations are analyzed in narrow frequency bands by means of the Partial Fourier Approximation. These temperature variations are compared with the corresponding cycles of solar activity in order to create long-term forecast models.