Model Performance in Simulating Global Monsoon Features: Skill Evolution across CMIP Generations

Improving projections of future changes in the global hydrological cycle is essential in order to understand the potential impacts of climate change and develop appropriate strategies of mitigation and adaptation to their socio-economics implications. This improvement requires a rigorous global climate model (GCM) evaluation, considering that several models often misrepresent fundamental processes of the global climate system. Recently, monsoons have been seen not just as systems that affect regional hydrology and climate but as a dominant global mode referred to as Global Monsoon (GM). The GM is tied to processes of global atmospheric circulation such as seasonal precipitation variation, the migration of the Inter-Tropical Convergence Zone (ITCZ), and the variability of the Hadley and Walker cells. Additionally, it can be seen as the response of the climate system to the annual solar radiation cycle. In this context, it is essential to consider not only regions with a marked seasonal change in the direction of surface winds but also the variation of precipitation in the tropics and subtropics. Reliable representations of its main characteristics are crucial for global simulations and climate change projections. This work analyzes the ability of GCMs in three generations of the CMIP (phases 3, 5 and 6) to simulate the most relevant characteristics of the global monsoon and in regions with high seasonal precipitation variability. We considered different aspects of tropical circulation, annual precipitation, and surface wind variability and dominant oscillation modes of the most important hydroclimatic variables.