Abstract:

Winter precipitation in the Tuotuo River directly affects plateau snow cover, through heat and radiation fluxes, impacts the local climate and atmospheric circulation. We utilized the Arctic Oscillation Index to identify the years with positive and negative arctic oscillation anomalies and investigated the effects of these anomalies on winter precipitation at Tuotuo River meteorological station. We also analyzed the multi-time scale correlation between winter precipitation and arctic oscillation, and explored the possible response mechanism of winter precipitation to arctic oscillation anomalies. Results indicate that winter precipitation at Tuotuo River station is significantly affected by arctic oscillation, with a notable positive correlation on inter-decadal scale. Positive-anomaly years of arctic oscillation coincide with higher probability of abundant winter precipitation. This can be attributed to the weakening of east Asian winter monsoon over the plateau and the strengthening of the India-Burma trough in the southern part of the plateau which enhance the southwest warm and humid airflows from the northern Indian Ocean and the Bay of Bengal. Conversely, negative-anomaly years of arctic oscillation correspond with scarce winter precipitation. Because in negative-anomaly years, winter monsoon on the plateau intensifies, while the India-Burma trough weakens. As a result, the southwest warm and humid airflows are relatively weaker, hindering the northward movement of water vapor onto the plateau and causing a significant reduction in precipitation.

Key words: arctic oscillation, winter precipitation, cross wavelet transform, Tuotuo River