摘要：Abstract Availability of water resources is significantly affected by changes in seasonal rainfall, with water often in short supply when most needed. The majority of current research focuses on the impacts of multiyear drought, using monthly or annual average rainfall to investigate impacts to water resources. Here, we use daily rainfall to evaluate changes in dry spells lengths, defined as the continuous number of days without rain, and investigate how these changes may impart stresses on water resources in warmer summer seasons globally. We use over 100 years of precipitation and temperature data across the world, arranged into warm and cold groups of years on the basis of mean summer temperature. These warm and cold groups are then compared to demonstrate an overwhelming tendency for warmer summers to contain longer dry spells globally. This difference in dry spell length in warmer summer seasons is argued to have far reaching ramifications in warmer summers. For some of the largest cities in the world, vulnerability of water resources, which is a measure of the magnitude or severity of the water availability deficit, is shown to be on average 30% higher due to longer seasonal dry spells in warmer summers. Such an impact points to a need to reassess water resources plans and policies to include the impacts of seasonal dry spells, especially relating to large urban populations around the world.
