۱- Introduction

۲- Methods

۳- Results

۴- Discussion

۵- Summary and conclusions

References

Abstract

The spatiotemporal monitoring of droughts is a complex task. In the past decades, drought monitoring has been increasingly developed, while the consideration of its spatio-temporal dynamics is still a challenge. This study proposes a method to build the spatial tracks and paths of drought, which can enhance its monitoring. The steps for the drought tracks calculation are (1) identification of spatial units (areas), (2) centroids localisation, and (3) centroids linkage. The spatio-temporal analysis performed here to extract the areas and centroids builds upon the Contiguous Drought Area (CDA) analysis. The potential of the proposed methodology is illustrated using grid data from the Standardized Precipitation Evaporation Index (SPEI) Global Drought Monitor over India (1901-2013), as an example. The method to calculate the drought tracks allows for identification of drought paths delineated by an onset and an end in space and time. Tracks, severity and duration of the drought are identified, as well as localisation (onset and end position), and rotation. The response of the drought tracking method to different combinations of parameters is also analysed. Further research is in progress to set up a model to predict the drought tracks for particular regions across the world, including India (https://www.researchgate.net/project/STAND-Spatio-Temporal-ANalysis-of-Drought).

Introduction

Drought is a regional phenomenon that often covers large territorial extensions (World Meteorological Organization WMO, 2006). It can occur anywhere in the world with severe consequences (impacts) in water resources and socioeconomic activities (Below et al., 2007; Sheffield and Wood, 2011; Tallaksen and Van Lanen, 2004; Wilhite, 2000). WMO stresses that to improve drought impacts mitigation, it is necessary to develop and implement national policies based on the best description and characterisation of drought (World Meteorological Organization WMO, 2006). There is no unique definition of drought. However, there is an agreement that it is an anomaly in precipitation and temperature that when extended over a region causes a lack of soil moisture, runoff and groundwater (Mishra and Singh, 2010; Van Loon, 2015). This lack of water is expressed by a drought indicator, which transforms the hydrometeorological variable into a value that is related to such a water anomaly (Mishra and Singh, 2011; Wanders et al., 2010). In drought monitoring, the drought indicators are generally used to identify the lack of water.