Effects of Rossby Wave Energy Propagation on Precipitation Anomalies in the Yangtze River Valley

Based on the 1966-2015 NCEP/NCAR reanalysis data and the precipitation data in the Yangtze River valley, the characteristics of Rossby wave energy was studied before the period of Meiyu, during and after Meiyu, both in heavy and light Meiyu years. The results show that:

(1).In heavy Meiyu years, the wave packet at the eastern Arabian Peninsula is strong, and the dispersal of wave packet energy to the downstream is more active. During Meiyu period, there are two waveguide regions in the middle and upper reaches of the Yangtze River valley, and then, the waveguide regions weaken and disappear. In the light Meiyu years, the characteristics of Rossby wave energy are reverse.

(2). The wave-activity fluxes in the north of the middle and lower reaches of the Yangtze river valley, strengthens during Meiyu and weakens after Meiyu in heavy Meiyu years, while weakens continuously in light Meiyu years. Before Meiyu, the wave-activity fluxes are weak in heavy Meiyu years and strong in light Meiyu years.

(3).The wave energy of westerly jet was converted to effective potential energy of basic flow and disturbance. Above the north of the Yangtze River valley is mainly distributed as "the wave sink region-the wave source region - the transition region" in heavy Meiyu years, and it distributed as "the wave sink region-the wave source region-the wave source region" in light Meiyu years. The westerly jet provides a good transport channel for the propagation of Rossby wave. The absence of the wave sink region before Meiyu in light Meiyu years is an important reason that the propagation of Rossby wave is less vigorous than that in heavy Meiyu years.

Key words: The Yangtze River valley, Meiyu, Rossby Wave Energy, Westerly jet

Acknowledgements：

This study was supported by National Natural Science Foundation of China Fund Project (41575066), National Science and Technology Support Program (2015BAC03B05).