Influence of the Tianshan Mountains on Arid Central Asia

Arid Central Asia is roughly bisected at the Tianshan Mountains (a northern offshoot of the Tibetan Plateau) into an eastern and western area, each with unique climatological characteristics. The eastern desert (~75-115E, 35-55N) has a summer precipitation maximum, and the western desert (~50-75E, 35-55N) has a winter precipitation maximum. A new high-resolution (50 km atmosphere/land) global coupled climate model is run with the Tianshan Mountains removed to determine whether these mountains are responsible for the climatological east-west differentiation of Arid Central Asia. Multi-centennial simulations for the control and no Tianshan runs highlight statistically significant effects of the Tianshan. The Tianshan are found to fully explain the spatial separation of the deserts, but only partially explain their differences in precipitation climatology. The Tianshan also create a few unexpected remote effects: 1) enhancement of the east Asian monsoon due to the Tianshan's stationary wave train, and 2) remote warming of mountains farther east due to reduction of snow cover and corresponding albedo decrease. Arid Central Asia comprises the only significant midlatitude deserts, and is the site of widespread grassland degradation in recent years. This study helps clarify the basic climate of this unique region, and hopefully paves the way for better understanding and prediction of how it will respond to future climate and land-use change.