Quantile-based spatiotemporal risk assessment of exceedances

Structural characteristics of random field excursion sets defined by threshold exceedances provide meaningful indicators for the description of extremal behaviour in the spatiotemporal dynamics of environmental systems, and for risk assessment. In this paper a conditional approach for analysis at global and regional scales is introduced, performed by implementation of risk measures under proper model-based integration of available knowledge. Specifically, quantile-based measures, such as Value-at-Risk and Average Value-at-Risk, are applied based on the empirical distributions derived from conditional simulation for different threshold exceedance indicators, allowing the construction of meaningful dynamic risk maps. Significant aspects of the application of this methodology, regarding the nature and the properties (e.g. local variability, dependence range, marginal distributions) of the underlying random field, as well as in relation to the increasing value of the reference threshold, are discussed and illustrated based on simulation under a variety of scenarios.