Abstract
Abstract. Of all natural disasters, the economic and environmental consequences of droughts are among the highest because of their longevity and widespread spatial extent. Because of their extreme behaviour, studying droughts generally requires long time series of historical climate data. Rainfall is a very important variable for calculating drought statistics, for quantifying historical droughts or for assessing the impact on other hydrological (e.g. water stage in rivers) or agricultural (e.g. irrigation requirements) variables. Unfortunately, time series of historical observations are often too short for such assessments. To circumvent this, one may rely on the synthetic rainfall time series from stochastic point process rainfall models, such as Bartlett–Lewis models. The present study investigates whether drought statistics are preserved when simulating rainfall with Bartlett–Lewis models. Therefore, a 105 yr 10 min rainfall time series obtained at Uccle, Belgium is used as a test case. First, drought events were identified on the basis of the Effective Drought Index (EDI), and each event was characterized by two variables, i.e. drought duration (D) and drought severity (S). As both parameters are interdependent, a multivariate distribution function, which makes use of a copula, was fitted. Based on the copula, four types of drought return periods are calculated for observed as well as simulated droughts and are used to evaluate the ability of the rainfall models to simulate drought events with the appropriate characteristics. Overall, all Bartlett–Lewis model types studied fail to preserve extreme drought statistics, which is attributed to the model structure and to the model stationarity caused by maintaining the same parameter set during the whole simulation period.
Highlights
Drought impacts on the environment and on the economy are among the highest of all natural disasters due to their longterm and extensive scale (Wilby and Wigley, 2000)
Drought events were identified on the basis of the Effective Drought Index (EDI), and each event was characterized by two variables, i.e. drought duration (D) and drought severity (S)
This study aims at investigating whether rainfall series simulated by the Bartlett–Lewis (BL) models can be used for drought analysis, as it can be questioned whether those models are able to reproduce drought statistics
Summary
Drought impacts on the environment and on the economy are among the highest of all natural disasters due to their longterm and extensive scale (Wilby and Wigley, 2000). There are two main challenges with respect to the statistical analysis of droughts. Unlike extreme rainfall or flood problems, drought may last from several months to years; the first challenge consists of retrieving a historical climate data set which is sufficiently long for analysis. Precipitation data, being the most important variable for drought investigation, is not always available from observations for such a long period. In the latter case, one may consider the use of stochastic point process rainfall models, which allow for generating extremely long rainfall time series with similar statistics to what was observed (Verhoest et al, 2010)
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