A potential rule of thumb for hourly rainfall?
Future global warming will be accompanied by more intense rainfall and flash floods due to increased evaporation, as a consequence of higher surface temperatures which also lead to a higher turn-around rate for the global hydrological cycle. In other words, we will see changing rainfall patterns. And if the global area of rainfall also shrinks, then a higher regional concentration of the rainfall is bound to lead to more intense downpours (the global rainfall indicator is discussed here).
Even with successful mitigation and cut in CO2-emissions, there will be a need for climate change adaptation (e.g. keeping the global warming below 2°C according to the Paris accord). We must be better prepared for more water in inconvenient forms and critical infrastructure may need to be upgraded to withstand it.
Engineers typically make use of so-called intensity-duration-frequency (IDF) estimates to design buildings, bridges or roads that are dimensioned to weather these conditions. Farmers need to know how to manage their fields to avoid erosion and loss of crops. Hence, IDF curves are useful for climate adaptation.
The IDF curves traditionally need sub-daily rainfall measurements (e.g. rainfall recorded every hour) which are not so common everywhere. The standard commonplace rain gauge data, however, record the rainfall accumulated over 24-hr segments (Figure 1).
https://www.realclimate.org/index.php/archives/2021/03/a-potential-rule-of-thumb-for-hourly-rainfall/#more-23474
