The summer rainfall in the eastern Tibetan Plateau (TP) is positively correlated with the sea surface temperature (SST) in the tropical southeastern Indian Ocean (SEIO). It is found that their relationship has enhanced significantly during the second period of 1984–2015 (P2) compared to the first period of 1951–1983 (P1). The anomalous anticyclone to the south of the TP is the major factor favoring more tropical moisture transported to the eastern TP (ETP) and the resultant above-normal-rainfall anomalies in the ETP in both the two epochs. However, the anomalous anticyclone and equatorial easterly anomalies associated with the warm SEIO SST anomalies is much stronger in P2 than those in P1. The warm SEIO SST anomalies are accompanied by a stronger El Niño in the preceding winter. It results in simultaneous warmer SST anomalies in the tropical Indian Ocean and colder SST anomalies in the equatorial central Pacific in P2. On the one hand, the excited meridional circulation induces suppressed convection leading to an anomalous anticyclone to the south of the TP. The anomalies of enhanced convection in the tropical eastern Indian Ocean and the downdrafts in the central Pacific favor the stronger equatorial easterly anomalies on the southern flank of anticyclone. On the other hand, the increased warming in the Indian Ocean basin produce an enhanced anticyclone and suppressed convection over the western North Pacific by emanating Kelvin waves. The diabatic cooling of suppressed convection induces the anomalous anticyclone to the south of the TP by exciting westward-propagating Rossby waves.
We investigated the relationship between the spring tropospheric temperature over the Tibetan Plateau (TPT) and summer precipitation in eastern China on an interannual timescale using the monthly mean ERA-Interim reanalysis dataset, the HadISST dataset and the daily mean precipitation dataset for China. We found that there is a significant positive correlation between the spring TPT and summer precipitation in the North China−Hetao region. The relationship is manifested in the context of the East Asia–Pacific pattern teleconnection. In the high spring TPT index years, the geopotential height anomalies over East Asia and the western North Pacific present a negative phase of the East Asia–Pacific pattern teleconnection in the subsequent summer. This circulation pattern is beneficial for the water vapor transport from the western Pacific to inland, which further transport to the North China−Hetao region from the Yangtze River–Yellow rivers region. Anomalous upward motion occurs in the North China–Hetao region, which increases precipitation. The East Asian subtropical westerly jet shifts further north and the South Asian high weakens and shrinks westward. These conditions all favor an increase in precipitation over the North China–Hetao region. The spring TPT plays an important part in the prediction of summer precipitation in the North China−Hetao region. The improvement in the use of the spring TPT to predict summer precipitation in the North China–Hetao region is examined by comparing the prediction equations with and without the prediction factor of the spring TPT on the basis of the sea surface temperatures in key regions. After considering the impact of the spring TPT, the explanatory variance of the prediction equation for precipitation in the North China–Hetao region increases by 17.3%.
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