[A-AS09] [EE] 成層圏－対流圏相互作用　―統一領域としての新しい視点―

[AAS09-24] Is There a Stratospheric Pacemaker Controlling the Daily Cycle of Tropical Rainfall?

*坂崎 貴俊^1,2,3、Hamilton Kevin¹、Zhang Chunxi¹、Wang Yuqing¹ (1.ハワイ大学　国際太平洋研究センター、2.日本学術振興会海外特別研究員、3.京都大学生存圏研究所)

Rainfall in the tropics exhibits a large, 12-hour sun-synchronous variation with coherent phase around the globe. A long-standing, but unproved, hypothesis for this phenomenon is excitation by the prominent 12-hour atmospheric tide, which itself is significantly forced remotely by solar heating of the stratospheric ozone layer. We investigated the relative roles of large-scale tidal forcing and more local effects in accounting for the 12-hour variation of tropical rainfall. A model of the atmosphere run with the diurnal cycle of solar heating artificially suppressed below the stratosphere still simulated a strong coherent 12-hour rainfall variation (~50% of control run), demonstrating that stratospherically-forced atmospheric tide propagates downward to the troposphere and contributes to the organization of large-scale convection. The results have implications for theories of excitation of tropical atmospheric waves by moist convection, for the evaluation of climate models, and for explaining the recently-discovered lunar tidal rainfall cycle.

Sakazaki, T., K. Hamilton, C. Zhang, and Y. Wang (2017), Is There a Stratospheric Pacemaker Controlling the Daily Cycle of Tropical Rainfall?, Geophys. Res. Lett., 44, doi:10.1002/2017GL072549.