Linear and nonlinear teleconnections in global drought data

Occurrence and intensity of meteorological droughts is governed by a complex interaction of numerous factors, with an important role played by global atmospheric and oceanic circulation and activity of major internal climate variability modes. A significant imprint of large-scale teleconnections can be found in local drought regimes across the world, often with major implications for drought variability and predictability. In this analysis, potential links between local droughts (characterized here by gridded values of observational Standardized Precipitation Evapotranspiration Index (SPEI), employed in monthly time step, since 1901) and selected large-scale internal climate oscillations are investigated through various techniques of correlation and regression analysis, with special emphasis on identification and quantification of nonlinearities in drought responses. It is shown that while linear approach is sufficient for capturing the effects of many of the influential teleconnections, more complex nonlinear responses can be detected in some cases. Use of nonlinear techniques is therefore highly desirable if a complete picture of relationships affecting local drought variability is to be obtained.