Multi-scale weather and climate processes influence a wide variety of phenomena in the monsoon regions, including seasonal-to-decadal monsoon variabilities, active and break monsoon spells on sub-seasonal time-scales, monsoon synoptic systems (e.g., low pressure systems and depressions), severe and high-impact weather, among others. Improved understanding of these processes is essential to better represent them in weather and climate models. The topics to be covered in this theme focus on the key underlying physical processes across different scales, such as land-ocean-atmosphere interactions, remote teleconnections, large-scale organized convection, mesoscale convective systems, and cloud-aerosol interactions, that shape variations in the regional monsoons of the world.

Integrated observations of precipitation and heavy rainfall-producing weather systems in monsoon regions are important for better understanding of the underlying physical mechanisms and evaluating weather-and-climate models. The topics to be covered in this theme mainly include: results from recent field campaigns and satellite measurements of precipitation over monsoon regions; description of plans for upcoming deployments as well as proposals for coordinated international activities (such as MONEX-2029); evaluation of monsoon simulations utilizing newly available observational datasets from field campaigns and space-borne instruments; status of multi-platform precipitation data sets over global monsoon regions, gap areas and possible solutions.

There are major uncertainties in simulating and predicting regional monsoon processes and extremes such as persistent heavy precipitation and draughts. Topics to be covered in this theme mainly include: predictability of regional monsoon processes, precipitation extremes, and sub-seasonal to decadal timescale variability; large-ensemble simulations to better understand forced and internal monsoons’ variabilities; analysis of regional monsoon processes using global storm-resolving simulations; improving the monsoon simulation/prediction through development of advanced data assimilation and better model physical schemes, including application of AI techniques.

As the Earth's climate continues to warm, there have been changes in atmospheric circulation and weather phenomena worldwide including the monsoon regions, which are at least partially attributed to anthropogenic global warming. There are large uncertainties, however, in future projections of regional monsoons by state-of-the-art climate models. The topics to be covered in this theme include: changes in regional monsoon characteristics (such as length of monsoon season, timing of onset and retreat of monsoons; occurrence frequency, intensity, phase and distribution of precipitation); reasons for such monsoon changes, e.g., impacts of anthropogenic emissions of greenhouse gases and aerosols, and also land use/land type changes; strategies for reducing uncertainties in the future projections of regional monsoons; weather modification research and climate intervention research relevant to global and regional monsoons .

The topics in this theme will focus on transforming monsoon research to operations and societal services; application of climate prediction and projections in various sectors (such as agriculture, energy, and water); quantification and communication of uncertainties associated with monsoon prediction and projection; use of AI/ML for preparing sector specific predictions and projections; assessing the socioeconomic impacts of monsoons; developing climate change adaptation strategies in monsoon regions.