Influence of August Asian–Pacific Oscillation on September Precipitation in Northern Xinjiang

Abstract

For arid and semi-arid regions like Xinjiang, analyzing the spatiotemporal patterns of September precipitation and their atmospheric circulation teleconnections is crucial for ecosystem preservation. This research examined how the August Asian–Pacific Oscillation (APO) influenced the September precipitation patterns in northern Xinjiang. The results show that the thermal anomalies resulting from the August APO exhibited persistence into September, triggering atmospheric circulation anomalies that ultimately affected the precipitation patterns in northern Xinjiang, with a notable negative correlation. The positive (negative) August APO phase corresponded to reduced (increased) mid-tropospheric geopotential heights over Asia and the Arabian Sea, significantly enhancing anomalous cyclonic (anticyclonic) circulation patterns in these regions. These circulation patterns induced anomalous northerlies (southerlies) over northern Xinjiang and the region from eastern Iran to the Persian Gulf, thereby reducing (increasing) the moisture transport from the Arabian Sea. Furthermore, the anomalous divergence (convergence) of cold/warm air masses and subsidence (ascent) motions exacerbated (enhanced) these effects, ultimately suppressing (enhancing) the September precipitation in northern Xinjiang.