A joint remote-sensing based index for drought identification and characterization in the Caribbean Islands

Drought is a natural hazard originating from a lack of precipitation. Its impacts are delayed, non-structural and spread over large areas (Wilhite, 2000). Drought characterization, through the determination of onset, offset, severity, intensity and duration, is crucial to manage and reduce the risk related to this extreme event. More than 100 indices have been proposed to monitor drought, each one with its aim and specificity. A single drought monitoring variable is insufficient to effectively determine drought features. Severity and intensity should be monitored at frequent time-steps. In addition, drought monitoring can be a hard task in countries with sparse gauges and few meteorological stations on the ground. The present study proposes a new index, SP&VH, developed by combining two of the most common variables used in drought monitoring: the Standardized Precipitation Index (SPI, Mckee et al, 1993) and the Vegetation Health Index (VHI, Kogan, 1990), derived from satellite-based data. The new index shows some interesting features: it is remote-sensing based, weekly updated and it can be computed over the entire globe at a proper spatial resolution. The index has been validated against text-based information retrieved for a specific case study (Haiti).