Urbanization-induced compression effect accelerates and amplifies dry-wet abrupt alternations in Chinese cities

Area of Science:

• Environmental Science
• Hydrology
• Urban Climatology

Background:

• Rapid urbanization significantly impacts hydrometeorological extremes.
• The effects of urbanization on compound dry-wet abrupt alternation (DWAA) are not well understood.

Purpose of the Study:

• To analyze the multi-scale effects of urbanization on DWAA in Chinese cities.
• To investigate the mechanisms driving urbanization-induced DWAA changes.
• To project future DWAA trends under different scenarios.

Main Methods:

• Integration of high-resolution observations and Weather Research and Forecasting (WRF) model simulations.
• Multi-scale analysis across city, pixel, and intra-urban areas.
• Assessment of future climate projections and population exposure.

Main Results:

• Urbanization compresses DWAA timescales and amplifies dry-to-wet and wet-to-dry transition severity in ~35% of Chinese cities.
• The compression effect is prevalent within urban areas (50%-95%), especially at expanding fringes.
• Coupled atmospheric-surface modifications, including urban heat/dry islands and boundary layer dynamics, drive these changes.

Conclusions:

• Urbanization significantly alters DWAA, leading to compressed timescales and intensified extremes.
• Future projections indicate a substantial increase in exposed populations and exacerbated DWAA impacts by 2100.
• Adaptation strategies for urban water management are crucial to address altered hydroclimatic timescales and amplified compound extremes.