ENSO modulation by mountain uplift

How climate changes will modify the behavior of El Niño/Southern Oscillation (ENSO) is one of the important questions in future climate projections. An investigation under different climate forcing gives us a good insight on the mechanism of ENSO variability and its changes. In this paper, sensitivity on ENSO by progressive mountain uplift is investigated with an atmosphere–ocean coupled general circulation model. We used eight different mountain heights: 0% (no mountain), 20, 40, 60, 80, 100 (control run), 120, and 140%. Land–sea distribution is the same for all experiments and all mountains in the world are uniformly varied. Systematic changes in precipitation and circulation fields as well as SST are obtained with progressive mountain uplift. In the summertime, the precipitation area moved inland of the Asian continent with mountain uplift, while the Pacific subtropical anticyclone and associated trade winds became stronger. The western Pacific warm pool and ENSO also systematically changed. When the mountain height is low, a warm pool is located over the central Pacific due to weak trade winds in the Pacific. The model ENSO is strongest, its frequency longest, and is most periodic in the no mountain run. The model ENSO becomes weaker, shorter and less periodic when the mountain height increases. Strengthening the mean state trade winds and narrowing meridional extent of equatorial wind and ocean response by mountain uplift would be responsible for ENSO modulation.