The Solar Precipitation Regime during the East Asian Summer Monsoon and the East Asia/Pacific Teleconnection

Abstract:

A precipitation regime during the East Asian summer monsoon modulated by the 11-yr SC is investigated in this study. The first empirical orthogonal function (EOF) mode of precipitation in the East Asian meiyu rainy season (the reverse variation of precipitation in northern and southern China) is likely to be the solar precipitation regime. Moreover, we find that this regime is closely related to the East Asia/Pacific teleconnection (EAP) wave train in the western Pacific. The EAP in early summer is modulated by the solar signal in the stratosphere to a certain extent. The change of solar radiation results in the change of stratospheric chemical composition and heating rate. The two changes and their combined effect lead to the change of stratospheric thermal structure. Then it causes dynamic change, which is beneficial to the stratospheric westerly anomaly in the middle and high latitudes, and causes the scattering of planetary waves to propagate more to the equator. It converges with the northward propagating planetary wave caused by the monsoon onset anomaly near 25 °N in the subtropical zone, resulting in the east wind anomaly in the subtropical region. On the other hand, before the onset of the monsoon (early May), westerly and thermal anomalies in the tropical stratosphere propagated downward to the troposphere. During the monsoon onset period (mid-May), these anomalies propagated upward and northward, which caused the convective activity anomalies and meridional temperature gradient changes in the off-equatorial region. The variation of meridional temperature gradient also leads to zonal wind anomaly (westerly anomaly to polar side and easterly anomaly to equatorial side). This series of zonal wind anomalies can explain the characteristics of the EAP wave train anomaly response to the 11-yr SC, and further explain the response of the precipitation EOF1 to solar activity.

Keywords: solar cycle, precipitation, monsoon, the EAP teleconnection, decadal variation