Abstract
Abstract. Since drought is a multifaceted phenomenon, more than one variable should be considered for a proper understanding of such an extreme event in order to implement adequate risk mitigation strategies such as weather or agricultural indices insurance programmes or disaster risk financing tools. This paper proposes a new composite drought index that accounts for both meteorological and agricultural drought conditions by combining in a probabilistic framework two consolidated drought indices: the standardized precipitation index (SPI) and the vegetation health index (VHI). The new index, called the probabilistic precipitation vegetation index (PPVI), is scalable, transferable all over the globe and can be updated in near real time. Furthermore, it is a remote-sensing product, since precipitation is retrieved from satellite data and the VHI is a remote-sensing index. In addition, a set of rules to objectively identify drought events is developed and implemented. Both the index and the set of rules have been applied to Haiti. The performance of the PPVI has been evaluated by means of a receiver operating characteristic curve and compared to that of the SPI and VHI considered separately. The new index outperformed SPI and VHI both in drought identification and characterization, thus revealing potential for an effective implementation within drought early-warning systems.
Highlights
Every year droughts affect an increasing number of people
This finding is in agreement with previous studies such as those of Hongshuo et al (2014), which found that the vegetation health index (VHI) and SPI3 have the highest correlation with croplands, whereas the VHI and 6-month standardized precipitation index (SPI) have the highest correlation with forest in the southwest of China, and Ma’rufah et al (2017), which found that significant correlation coefficient values of the SPI3 and VHI are common in the southern part of Indonesia
The new composite index proposed in this paper, the probabilistic precipitation vegetation index, PPVI, is a powerful tool since it can identify events of vegetation stress and, at the same time, select from among those the ones due to drought, thanks to the use of both the VHI and the SPI
Summary
Every year droughts affect an increasing number of people. In the years from 2014 to 2018, more than 70 drought events were reported all over the world and about 450 million people suffered because of drought-related impacts (CRED, 2017). Various definitions of the phenomenon have been proposed by different institutions, such as the World Meteorological Organization (WMO), the Food and Agriculture Organization (FAO), and the United Nations Convention to Combat Desertification (UNCCD). All the institutions focus their attention on a specific aspect of drought: the WMO on the lack of precipitation, the FAO on the decline in crop productivity and the UNCCD on the loss of arable land. Drought identification through an objective and automatic determination of drought onset, termination and severity allows for the timely adoption of appropriate risk management strategies, such as weather index insurance programmes (Barnett and Mahul, 2007), agricultural index insurance programmes (Jensen and Barrett, 2017), disaster financing (Guimarães Nobre et al, 2019; Linnerooth-Bayer and Hochrainer-Stigler, 2015) and early action planning (Drechsler and Soe, 2016)
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