Enhancement of annual precipitation range under global warming

In a warming climate, a wet region tends to get wetter and a dry region tends to get drier, which is associated with the “rich-get-richer” mechanism. Over regions that have clear wet and dry seasons, this means enhancement of annual precipitation range, i.e., a wet season gets wetter and a dry season gets drier. In this study, we examine changes in annual precipitation range induced by global warming. For a global average, rainfall over wet seasons indeed has an upward trend, while rainfall over dry seasons tends to decrease. This enhances the annual precipitation range. On a regional basis, on the other hand, the changes in annual precipitation range are much more complicated because the contribution of a dynamic component, which is associated with a change in the circulation, becomes important, e.g., the monsoon regions. We further examined a vertically integrated moisture budget to understand the cause for the changes in annual precipitation range.