Pre-rain index
The pre-rain index or pre-moisture index is a parameter used for use in hydrological models. It is a measure of the soil water content based on the local amount of precipitation . The pre-rain index is determined by the weighted sum of the previous daily precipitation values, with the weights decreasing as an exponential or reciprocal function of time.
Several models are used that use observation periods of different length, of which a 30-day (VN30) or 21-day (VN21) period is predominantly used. Additional dependencies can also be taken into account, for example the potential evaporation depending on the season (pre-rain index according to Zaiß, 1989). With the help of these models, an impending heavy rain event can be assessed and the probability of a flood calculated in order to be able to issue severe weather warnings.
Individual evidence
- ↑ Lexicon of Geosciences Spektrum.de
- ↑ Dealing with heavy precipitation in Hesse, 2. Interim report KLIMPRAX_AP2 ( online ), November 3, 2016 / page 10