Impacts of the Surface Potential Vorticity Circulation over the Tibetan Plateau on the East Asian Monsoon in July

Based on the definition of potential vorticity substance (W) and its equation, an index “iPV” representing leading mode surface circulation (PVC) over Tibetan Plateau is defined to characterize orographic (PV) forcing atmospheric general circulation. The relationships between iPV East Asian monsoon in July, as well Silk Road pattern Eurasia, are investigated interannual time scale. Results show that July closely related variability monsoon. Corresponding positive phase with negative (positive) PVC north (south) plateau, strong PV anomalies westerly flows develop troposphere plateau. Consequently, downstream region, zonal advection increases height just above Jianghuai Meiyu front, which conducive generation upward movement. Over area, upper controlled by eastward shifted South High. In lower troposphere, southwesterly flow anomaly northwestern side strengthened western Pacific subtropical high transports abundant water vapor north, forming a convergence formation large-scale precipitation along front. from partial correlation analysis also demonstrate link plateau affected very little pattern, whereas plays key “bridging” role influence