Mega-drought Detection and Prediction in the Central Sierra Derived from the Reconstruction of the Mt. Rose SWE Record for Water Years 972 - 2031 Using the Reversal of the Sun's Magnetic Field

We have shown in several previous papers one of the major driving forces of winter precipitation in the Sierra are the reversal of the sun's magnetic field and a statistically independent "carrier" signal being generated by the Earth's large-scale atmospheric circulation. We present in this paper an extension of our wavelet analysis methods to include the period 971 to 2031. We applied our model using a recently published tree ring reconstruction of solar modulation covering the last millennium to reconstruct the Mt. Rose SWE record over the period WY 972 to WY 1912. We then used the International SSN combined with the accepted SSN prediction model for Solar Cycle 25 to estimate the Mt. Rose SWE over the time span 972-2031 . Our model is confirmed by a high correlation with the Mt. Rose SWE record over the period 1913 to 2021. The amplitude modulation of the sun's magnetic field, the Gleissberg Cycle (GC), is determined to be a time varying signal that resets approximately every 100 years. In addition, the GC has an amplitude modulation with a period of approximately 2517 years. This is the Hallstatt cycle that has been reported in cosmogenic radioisotopes (14C and 10Be) and in paleoclimate records throughout the Holocene. There is compelling evidence the Hallstatt oscillation is coherent to a repeating pattern of planet motions and is therefore astronomical in origin. The relatively short period of 276 years (ISSN (1755-2031)) selected for our previous papers is only 10% of the Hallstatt cycle and hence its effect was considered negligible. However, for the longer period considered in this paper, the effects of the Hallstatt cycle had to be included. We report on the mega-drought conditions that were occurring in the Sierra mountains before, during, and after the medieval period.