Publikationsdatum:
2023-07-27
Beschreibung:
The influence of periodic changes in solar irradiance on climate was investigated using the Kiel Climate Model. For that data of a control integration as well as of four runs with different solar constants varying in period (100 and 1000 years) and amplitude (1 and 2 W/m2) have been analysed. The aim of this investigation was to distinguish between anomalies caused by internal variability and those raised by the external forcing. In time series analysis of temperature and precipitation, it turned out that the integration with longer period and higher amplitude revealed strongest differences to the control integration. The centennial runs showed clearly less impact of the solar forcing. These results could be confirmed by the evaluation of the zonal means of surface temperature and precipitation and further by composite analysis. For all runs comparable anomaly patterns showed up, except for the weak centennial forcing run for which no clear impact was found.
Three regions drew special interest: the northern North Atlantic where temperature differences are at the first glance in contradiction to the forcing, the Barents Sea with the strongest anomalies over the whole Northern Hemisphere, and the Northwestern Pacific with inconsistent behaviour but strong anomalies in comparison to the surrounding regions. It turned out that in all three regions feedback mechanisms are responsible for these eye-catching anomalies. In the North Atlantic, a negative feedback in which the Atlantic Meridional Overturning Circulation plays the dominant role counteracts the direct forcing effects. Positive ones, which are also important features of the internal variability, are the "engines" in the other two regions. The investigation of the global anomaly patterns did not provide a strong seasonality. However, in the three above mentioned regions the differences from the control run turned out to be most prominent in winter, whereas there are, if any, only small effects in summer. The impact of the solar forcing on both the strength and also in some cases the pattern of the response is dependent on amplitude and period.
Materialart:
Thesis
,
NonPeerReviewed
Format:
text
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