Quantification of the Direct Solar Impact on Some Components of the Hydro-Climatic System

Abstract

This study addresses the causal links between external factors and the main hydro-climatic variables by using a chain of methods to unravel the complexity of the direct sun–climate link. There is a gap in the literature on the description of a complete chain in addressing the structures of direct causal links of solar activity on terrestrial variables. This is why the present study uses the extensive facilities of the application of information theory in view of recent advances in different fields. Additionally, by other methods (e.g., neural networks) we first tested the existent non-linear links of solar–terrestrial influences on the hydro-climate system. The results related to the solar impact on terrestrial phenomena are promising, which is discriminant in the space-time domain. The implications prove robust for determining the causal measure of climate variables under direct solar impact, which makes it easier to consider solar activity in climate models by appropriate parametrizations. This study found that hydro-climatic variables are sensitive to solar impact only for certain frequencies (periods) and have a coherence with the Solar Flux only for some lags of the Solar Flux (in advance).

Selection of Optimal Palmer Predictors for Increasing the Predictability of the Danube Discharge: New Findings Based on Information Theory and Partial Wavelet Coherence Analysis

“…The methods presented here complement previous studies conducted in different geographical areas [ 11 , 18 , 19 , 20 ] and are generally useful for implicitly understanding aspects of short-term climate variability and its hydrological impact.…”

“…The last two averages for the periods between 8–15 and 22–30 years, respectively, can highlight the influence of the Schwabe and Hale solar cycles [ 18 , 19 , 20 , 44 , 82 , 83 , 84 , 85 , 86 ].…”

“…In our previous investigations [ 18 , 19 , 20 , 44 ], as in the present study, we separately considered the influence of atmospheric predictors, such as Palmer indices, large-scale climate indices, and indicators of solar/geomagnetic activity, regarding their information content, on the Danube discharge.…”

“…Regarding the multiple wavelet coherence ( mwc ) developed by Hu and Si (2016) [ 3 ], the authors of this study applied it to find multiple coherence between different large-scale climate indices and the Danube discharge and between climate indices and indicators of solar/geomagnetic variability [ 18 , 19 , 20 ].…”

“…This study is based on time series from the twentieth century (1901–2000), and investigations were performed separately for each of the four seasons. This time interval and the seasonal averages were considered in order to be able to compare the results obtained here with those obtained in our previous investigations [ 18 , 19 , 20 , 44 ].…”