Abstract
Abstract. This study proposes a drought indicator that combines the Standardized Precipitation Index (SPI), the anomalies of soil moisture and the anomalies of the fraction of Absorbed Photosynthetically Active Radiation (fAPAR). Computed at the European level, the Combined Drought Indicator (CDI) gives a synthetic and synoptic overview of the drought situation using a classification scheme. Derived from the integration of the three individual indices, this classification scheme is composed of three warning levels: "watch" when a relevant precipitation shortage is observed, "warning" when this precipitation shortage translates into a soil moisture anomaly, and "alert" when these two conditions are accompanied by an anomaly in the vegetation condition. The design of the CDI includes the study of the relationship between the three individual indices. To achieve this, the SPI-3 (3-month SPI) was computed using the precipitation data obtained from a set of weather stations located in different agricultural areas of Europe, while the soil moisture and fAPAR data were extracted from the pixels of the respective grids surrounding these stations. The CDI is assessed for the main drought episodes of Europe between 2000 and 2011, using reported data from different sources, such as the EM-DAT Emergency Events Database and Eurostat annual yield estimates. The capability of the CDI to serve for drought early warning is evaluated as well as its robustness against false alarms. The indicator has been spatially implemented for the entire continent using different information layers of the European Drought Observatory. These layers correspond to SPI-3 grids derived from interpolated weather station precipitation data, anomalies of fAPAR from the MERIS Global Vegetation Index and anomalies of soil moisture obtained using the LISFLOOD distributed hydrological model. Maps of the CDI obtained for the European drought event in spring 2011 are shown and discussed, evaluating its operational applicability. To conclude, the main limitations of the indicator are presented and possible avenues for improvement are discussed.
Highlights
Agricultural drought can have severe economic and social consequences, especially in regions with limited water resources or with imbalances between water demand and natural supply capacity
Anomalies of precipitation (SPI-3), soil moisture and fraction of Absorbed Photosynthetically Active Radiation (fAPAR) are used as the basic indicators to design a prototype of the so-called Combined Drought Indicator (CDI), characterising the different stages of the agricultural drought cause–effect relationship
The CDI depicts the spatial extent of a drought situation and gives an overview of the possible consequences for agriculture, classifying the affected areas with a watch when there is a precipitation deficit, a warning when this precipitation deficit leads to a soil moisture deficit, and an alert when the two previous conditions result in a reduction of the vegetation production
Summary
Agricultural drought can have severe economic and social consequences, especially in regions with limited water resources or with imbalances between water demand and natural supply capacity. As a result of such sizeable losses incurred due to drought, there is a need to operationally provide indicators that correctly estimate the onset, severity and cessation of a drought event so that the most effective mitigation responses, such as water conservation measures and water resource allocation strategies, can be triggered. The primary driver of drought is a shortage of precipitation, its definition may depend on, amongst others, location, time of the year, landuse type, and context of the impact. Agricultural drought can be thought of as the result of a shortage of precipitation over a particular timescale that leads to a soil moisture deficit that limits water availability for crops to such an extent that yields are reduced. A range of indicators is used to detect and monitor agricultural drought, which are typically based on the use of meteorological observations and estimates from remote sensing and/or modelling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
