Cooling the air: assessing the evaporative cooling potential of sea water spraying as an extreme heat intervention

Extreme heat is emerging as one of the deadliest weather-related hazards under global warming. In response, a growing range of weather and climate interventions has been proposed to locally mitigate extreme thermal stress. The spraying of water into the air is a well-established technique for direct evaporative cooling at small scales, such as in urban or industrial environments. In this study, we assess the potential for larger-scale sea water spraying as a localized extreme heat intervention.

We first quantify the maximum evaporative cooling potential of liquid water spraying and its dependence on air temperature and relative humidity. Under hot and dry conditions, theoretical cooling exceeding 20 °C can be achieved, providing an upper bound for realistic applications. We then employ Large Eddy Simulations (LES) to investigate kilometer-scale cooling of the lower atmosphere in coastal regions experiencing sea-breeze conditions in hot and dry climates. A key innovation of this study is the introduction of sea water spraying from wind turbines, which we compare with spraying from lower infrastructures such as platforms or boats.

The resulting impacts on near-surface temperature and human thermal comfort indices are evaluated, highlighting potential cooling benefits during extreme heat events. Finally, we examine how such cooling influences plume rise, a key process for Marine Cloud Brightening. Our results demonstrate that physically bounded, localized atmospheric interventions may offer a useful tool to mitigate extreme heat in vulnerable regions, while providing insight into the effectiveness and limitations of weather- and climate interventions.