Precipitation efficiency constraint on climate change

Precipitation efficiency (PE) relates cloud condensation to precipitation and intrinsically binds atmospheric circulation the hydrological cycle. Due PE’s inherent microphysical dependencies, definitions estimates vary immensely. Consequently, sensitivity greenhouse warming implications for climate change are poorly understood. Here, we quantify role in by defining a simple index ϵ as ratio of surface condensed water path. This macroscopic metric is reconcilable with PE measures higher associated stronger mean Walker circulation. We further find that state-of-the-art models disagree on sign magnitude future changes. disagreement originates from models’ convective parameterizations. Critically, increasing under warming, line cloud-resolving simulations, show greater slowdown large-scale Hadley circulations two-fold increase extreme rainfall than decreasing ϵ. Falling raindrops play an essential but as-yet unquantified planetary change. Here authors use concept establish critical predicting tropical precipitation.