High Resolution Atmospheric Model (HiRAM) Projection of Global Warming Impact on the Asian Summer Monsoon

Abstract:

By investigating the Geophysical Fluid Dynamics Laboratory (GFDL) global High Resolution Atmospheric Model (HiRAM), following the most extreme one of the Representative Concentration Pathway scenarios (RCP8.5), we explore a possible modulation of the Asian summer monsoon under global warming. At about 23km horizontal grid size, more realistic topographic effects included in the HiRAM benefit the monsoon modeling; for example, a substantial effect of the mesoscale mountain ranges in South Asia (includes Southeast Asia) on anchoring and enhancing precipitation as well as the monsoon circulation. The projected changes of the monsoon subsystems are significant in South Asia, East Asia, and the western North Pacific (WNP), and the changes are likely related. The monsoon response to global warming provides an avenue for exploring the monsoon internal connection. However, details about the potential interaction between various monsoon subsystems remain unclear; in particular, what it is sensitive to, and how it is connected to large-scale circulation.

We also focus on the modulation of the monsoon seasonality. In South Asia, direction of the monsoon precipitation response in the early summer (reduced) is opposite to in the late summer (enhanced). The projected precipitation changes of South Asia could be connected to the projected changes of the monsoon subseasons in the East Asia-WNP domain. The latter can be primarily characterized by the Meiyu-Baiu rainy season and the WNP monsoon. We are also finding that the changes of thermal and dynamical condition under global warming alter the extreme precipitation and the tropical cyclone formation. Mechanism leading to the regional and subseasonal contrast of the monsoon is being investigated.