Solar Cycle Signature in Decadal Variability of Monsoon Precipitation in China

Monthly high-resolution land surface precipitation data from 1901 to 2006 associated with sunspot number (SSN) data is investigated for the relationship between summer precipitation in China and the decadal solar variability. Generally, on a national scale, precipitation is poorly correlated with SSN. However, in many regions, the long-period (>8 years) variability in summer precipitation is significantly (at >95% confidence level) correlated to SSN. Absolute value correlation coefficient can exceed 0.48 (at >99% confidence level) in some regions. If only the decadal (9–13 years) precipitation component is considered, the correlation becomes stronger with a maximum (minimum) correlation coefficient of 0.73 (–0.73) (at >99.9% confidence level). Considering that the decadal component is the most important factor among precipitation’s low-frequency signals in the high correlation areas (because it explains more than 50% of the precipitation’s low-frequency variance), it can be concluded that solar variability seems to dominate the long-period variation of summer precipitation in these areas. Furthermore, in these high correlation areas, temporal variation patterns in the power spectrum of summer precipitation is similar to that of SSN, strongly suggesting that there is a very likely physical link between solar variability and precipitation in these regions. More convincing and direct evidence shows the significant difference of low-level monsoon flow between high and low solar activity years, which may cause the higher precipitation rate for high, rather than low, solar activity years in central China.