Impact of Asian orography on ENSO

Abstract

Tall mountain ranges such as the Tibetan Plateau and the Rocky Mountains play a significant role in shaping the climatological Northern Hemisphere zonal wind distribution and the stationary waves in the geopotential field. In this work we assess the influence of Asian orography on ENSO and its wintertime teleconnections by comparing a flattened-orography simulation to a control simulation using an ocean-atmosphere coupled model. We have found that the presence of the Asian orography is key to both ENSO and its teleconnection pattern. When the mountains are not present, El Niño and La Niña events decay more rapidly and the ENSO cycle has a higher frequency, is more regular, and is characterized by stronger sea surface temperature anomalies. The Northern Hemisphere winter teleconnection pattern in the geopotential field also changes significantly, with a new Rossby wave train emerging from Southern Asia and propagating northwestward, and a ridge appearing over Greenland