Leading Modes of Wind Field Variability over the Western Tibet Plateau

As the atmospheric circulation is the only media brings moisture from above the ocean to high mountains on the western Tibet Plateau (TP), the wind variability is of great importance to the water cycle centering at the western TP. This study thereby examines the leading modes of the wind fields over the western TP. The multivariate empirical orthogonal function (MV-EOF) analysis method is employed in this study to detect the dominant wind patterns above the western TP, which extracts the leading modes of the combined meridional and zonal wind variability at 200-hpa level in the region of 22°N-50°N, 50°E-92°E. Here, we find the first leading mode of the combined zonal and meridional wind field in annual mean and in most seasons (spring, summer and autumn) over the western TP show high similarity to the Western Tibetan Vortex (WTV), a large-scale atmospheric pattern recently recognized over the western TP. In winter, the WTV, however, is closer to the second leading mode. By moving the position of the same area surrounding the western TP and re-checking, we find the WTV is tied closely to geographical location of the western TP. In short, the WTV generally represents the first leading mode of the wind field in most seasons over the western TP. This study augments our knowledge on the wind variability over the western TP.