Unraveling multiscale relationship between Germany streamflow and global
SST using climate networks
Abstract
Exploration of SST-Streamflow connection unravels the large scale
climate influences that have a potential role in modulating local
hydrological components. Most studies exploring this relationship only
focus on seasonal or annual scales however, various atmospheric and
oceanic phenomena occur at different timescales, which need to be
considered. This study investigates the influence of sea surface
temperature (SST) on German streamflow, divided into Alpine, Atlantic
and Continental streamflow regions, at timescales ranging from
sub-seasonal to decadal by integrating wavelet transform and complex
network techniques. Wavelet transform is used to decompose the time
series into multiple frequency signals, and the spatial connections are
identified based on these decomposed signals for the 99 percentile
correlation coefficient value by applying network theory. The degree
centrality metric is used to evaluate the characteristics of the
spatially embedded networks. Our results re-establish known SST regions
that have a potential connection with the various streamflow regions of
Germany. Spatial patterns that resemble the North Atlantic SST
tripole-like pattern is predominant for Alpine streamflow regions at
lower timescale. Equatorial Atlantic Mode regions observed for Atlantic
streamflow at inter-annual timescale and Vb weather system connected
regions in the Mediterranean Sea have appeared for all the streamflow
regions of Germany. Besides, continental streamflow regions exhibited
combined characteristics of the Alpine and Atlantic streamflow spatial
patterns. In addition to the above regions, we also identify the scale
specific patterns in the Pacific, Indian and Southern Ocean regions at
different timescales ranging from seasonal to decadal scale.