A link between the global surface area receiving daily precipitation, wet-day frequency and probability of extreme rainfall

Both the total amount of precipitation falling on Earth’s surface and the fraction of the surface area on which it falls represent two key global climate indicators for Earth’s global hydrological cycle. We show that the fraction of Earth’s surface area receiving daily precipitation is closely connected to the global statistics of local wet-day frequency and mean precipitation intensity, based on the ERA5 reanalysis. Our analysis of the global statistical distribution of local temporal mean precipitation intensity μ revealed a close link between (1) its global spatial average ⟨μ⟩ and (2) the total daily precipitation falling on Earth’s surface divided by the global surface area fraction on which it falls. This correlation highlights an important connection, since the wet-day frequency and the mean precipitation intensity represent two key parameters that may be used to approximately infer the probability of heavy rainfall on local scales. We also found a close match between the global mean surface temperature and both the total mass of 24-h precipitation falling on Earth’s surface as well as surface area receiving 24-h precipitation in the ERA5 data, highlighting the dependency between the greenhouse effect and the global hydrological cycle. Moreover, the total planetary precipitation and the daily precipitation area represent links between the global warming and extreme precipitation amounts that traditionally have not been included in sets of essential climate indicators. A simple back-of-the-envelope calculation suggests that half of Δ⟨μ⟩ /Δ T = 0.47 mm/day can be explained by increased 24-h precipitation and half by a reduced fractional area of 24-h precipitation.