It is evident that anthropogenic climate change is already affecting weather and climate extreme events such as floods and droughts across the globe at an unprecedented rate. Such extreme events can result in hazards and disasters with associated, strong and negative impacts on the environment, socio-economy, and human health. This is particularly relevant in the urban environment, where half of the global population resides. Despite the increased awareness of the risks of extreme events, cities are highly prone to the associated hazards. Climate change is impeding the attribution and quantification of the risk of unprecedented hydrometeorological events.
Particularly in coastal megacities such as Shenzhen and Shanghai, hydrometeorological extremes may result in different types of floods: floods caused and modulated by storm surges such as typhoons in combination with tide (coastal floods), heavy precipitation events (pluvial floods) as well as large-scale riverine floods. Special emphasis is given to risk assessment of compounding events, i.e. co-occuring events of different extremes at nearly the same time and place such as coastal floods in combination with pluvial floods, as can be caused by typhoons.
Within this context, this SI aims to strengthen transdisciplinary physically based research activities worldwide, including hydrology, hydraulics, as well as meteorology and climatology. This SI will not address studies about adaptation measures, economic considerations, and policy recommendations for urban environmental development.

The inter-journal SI is open for all submissions within its scope. Submissions within the following subtopics (not restricted to those) will be considered.

1. Characteristics and process understanding of historical extreme events in the urban environment

• Analysis of changes in occurrence and magnitude in single and compound extremes
• Identification of the relevant underlying physics (drivers such as teleconnections and circulation patterns) associated with extreme events

2. Attribution and impact analysis of extreme events in the urban environment

• Development of theoretical (statistical) frameworks for identifying modulators and drivers of (compounding) extreme events such as multivariate or vine copulas
• Development of process-based compartment-crossing modeling systems from climate to hydraulic models (e.g., storm surge modeling in coastal cities) for assessing extreme-event-induced hazards and disasters
• Attribution and impact studies of future climate change on urban extreme events from all over the world