The Stability of Teleconnections Between Large-Scale Atmospheric Variation and Hydrological Systems

Abstract:

Land surface hydrology is influenced by atmospheric controls at a wide range of spatial scales. However, larger scale atmospheric variation can be particularly useful when considering hydrological variation over longer time periods. Here, a series of examples are discussed which demonstrate both the increased understanding that can be obtained from identifying relationships between large-scale climate and land surface hydrology, together with their potential limitations, particularly in light of decadal-scale variability. The first set of examples relate to a series of process-based relationships between modes of atmospheric variation and both river flow and meteorological drought in the north Atlantic-European region. The identification of these relationships, including the cascade of processes linking atmospheric circulation to land surface hydrology, provides a framework within which ocean-atmosphere-land surface hydrology relationships and teleconnections in this region can be understood. Although many of these relationships appear stable (within the time period of analysis), other examples of large-scale climate relationships to land surface hydrology have been shown to vary over time. For example, a series of investigations in New Zealand have shown that climate-river flow relationships based on certain patterns of large-scale atmospheric variation are strong in some time periods yet weak or non-existent in others. In part, this may be due to interaction between relatively quick and slow varying components of the climate system (particularly associated with the Inter-decadal Pacific Oscillation). As such, it is essential to understand the decadal-scale context within which teleconnections between large-scale atmospheric variation and hydrological systems operate, before such relationships can be used as a means to reduce uncertainties in modelling hydrological changes.