The reconnaissance drought index: A method for detecting regional arid climatic variability and potential drought risk

- The annual initial reconnaissance drought index (RDIα12) is a single climate index.
- RDIα12 is higher for humid areas compared with other climatic conditions.
- RDIα12 summer values are lower than winter ones for nearly all climatic conditions.
- Semi-arid low lands (LL) are likely to change to hyper-arid due to climate change.
- Moderately wet LL are most likely to change to extremely dry due to climate change.

The impact of climate variability on water demand and availability in drylands is substantial. Establishing methods to analyse precipitation (P) and evapotranspiration data sets may generate useful tools that assist in drought recognition and regional variations therein. The authors developed an index that simultaneous integrates both these variables in climate variability analysis. This study proposes the alpha and normalised forms of the reconnaissance drought index (RDI) as a single climatic index for the recognition of geographical areas with differing drought characteristics and potential weather variability. The prime application is that the RDI combines in a single index both P and potential evapotranspiration. A more consistent trend of climate variability can be identified by applying time series of different durations of RDI compared to using time series of P and potential evapotranspiration separately. The researchers explore this approach using meteorological data form 24 locations representing arid, semi-arid (Mediterranean (MD), tropical (TR), continental (CN)), and humid climatic conditions. The method is then tested through application to the semi-arid Lower Zab River basin (LZRB) in Iran and Iraq. Findings show that many regions such as the LZRB will face major droughts, indicating that there is an urgent requirement to advance water management strategies.

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