The role of the North American continent in strengthening the Asian summer monsoon.

Abstract

Most studies on modern Asian monsoon formation focus on mechanisms arising within the Afro-Eurasian continent, while fewer compare the effects from remote continents. Here, we explore this question using a coupled climate model. We show that the existence of the North American continent is critical for the intensity of the Asian summer monsoon. The mechanism involves North America acting as an additional heating center, resulting in the strengthening and extension of oceanic advection toward the monsoon region. This is achieved via the Rodwell-Hoskins mechanism that strengthens the North Pacific subtropical high and through a widespread Northern Hemisphere heating that shifts the Hadly circulation subsidence center poleward. This teleconnection is independent of the presence of the Tibetan Plateau, and its impact on East Asian summer precipitation is found to be smaller but comparable to that of Tibet. The individual role of other continents outside Afro-Eurasia is found to be less important.