South Asian summer monsoon and subtropical deserts

The relationships between south Asian monsoon and northern hemisphere subtropical deserts have generated a lot of interest in recent times as both systems, despite contrasting climates, are expected to be severely affected by anthropogenic climate change. This review envisages two pathways for the monsoon-desert relationship. The first one hypothesizes a significant influence of the monsoon on subtropical deserts whereby convection over the Indian summer monsoon region induces Rossby-wave descent to its west. The second one proposes a very different perspective by emphasizing the potential role of northern hemisphere deserts on the Indian summer monsoon either through the changes of surface heating over the subtropical deserts or by dry air intrusions from arid regions into the monsoon domain. However, most current coupled climate models struggle to simulate realistically these monsoon-desert relationships due to various reasons, as documented in this chapter, calling for advances in coupled models with improved physical parameterizations.