Climate model simulation on the role of mountain uplift on Asian monsoon

Kitoh Akio

doi:10.5575/geosoc.111.654

To study the role of mountain uplift on Asian monsoon, a series of coupled ocean-atmosphere general circulation model experiments are performed. Mountains are uplifted from 0% (no mountain) to 140% where 100% corresponds to the control experiment. The land-sea distribution is the same for all experiments and mountain heights are varied uniformly over the entire globe. Systematic changes in circulation as well as precipitation fields are found with progressive mountain uplift. A north-south jump of the 500 hPa zonal wind axis around the longitude of the Tibetan plateau is found with mountain height higher than 60% between the winter and summer season. On the other hand the jet axis stayed in the northward position all the year round in the experiments with lower mountains. Summertime precipitation is confined in the deep tropics around 10 ºN in the no-mountain (M0) case, but it moves inland on the Asian continent with mountain uplift. Associated with this, an intensification of the Pacific subtropical anticyclone and trade winds is found. The Baiu-like precipitation belt in East Asia clearly appeared at mountains higher than 60%. Surface wind distribution over the Indian Ocean and the Maritime Continent region drastically changed by mountain uplift. Summertime southwesterly monsoon flow does not cover the northernmost Arabian Sea region so that upwelling is inactive all the year round when mountain is lower than 40%. Changes in climatic area based on Koppen-type climate classification are also investigated. It is found that desert area is the largest in the no-mountain case and decreases in its area extent with mountain uplift.<br>

Climate model simulation on the role of mountain uplift on Asian monsoon

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