Copula-based agricultural drought risk of rainfed cropping systems
Ribeiro A.F.S., Russo A., Gouveia C.M., Páscoa P.
Agricultural Water Management. DOI: http://dx.doi.org/10.1016/j.agwat.2019.105689
In a future climate, warmer and drier conditions are expected, and the associated negative impacts in agricultural productions are a major issue. Assessing the risk of drought hazard on agricultural systems is, therefore, of main importance in decision-making, with the aim of mitigating drought-related crop losses. In this study the agricultural drought risk is defined as the conditional probability of occurring crop-losses under drought conditions. We use the copula theory to estimate joint probability distributions describing the amount of dependence between drought conditions and crop yield anomalies of two major rainfed cereals in the Iberian Peninsula (wheat and barley), in the period 1986–2016. Further conditional probability distributions of the crop yield anomalies under different drought levels are obtained using the Standardized Precipitation Evapotranspiration Index (SPEI) and the satellite derived indices Vegetation Condition Index (VCI) and Temperature Condition Index (TCI). The results suggest that, in general, the joint behaviour of yield anomalies and drought conditions exhibits a dependence between the extreme values, whereas barley exhibits greater probabilities of joint extreme low values of yield and drought indicators. Moreover, while TCI is mainly used in copula models indicating greater probabilities of joint extreme high values of wheat and drought indicators (gumbel models), VCI and SPEI are mainly associated to copula models indicating greater probabilities of joint extreme low values (clayton models). The estimated conditional probabilities of occurrence of crop-loss are illustrated at the province level and suggest that agricultural drought risk increases with drought severity in most of the provinces.