Drought indices: aggregation is necessary or is it only the researcher's choice?

Abstract

Drought is a natural phenomenon caused by extreme and persistent precipitation shortage. This shortfall causes impacts on hydrology, agriculture, and the economy of a country. Secondly, drought/dryness has certain unique characteristics (severity, duration) among the natural hazards which makes it difficult to classify the persistent and subjective network of impacts. Drought classification is important to manage drought, allowing both quantitative evaluation and potential risk assessment planning. The simpler approach of drought indices made it easier for various researchers and organizations to classify drought. Several drought indices have been proposed at the national and global level to characterize hydrological, meteorological and agricultural droughts. Until now, there has been no widely agreed drought index among researchers. Therefore, researchers are trying to modify and reconstruct a simple, complete, and robust drought index for effective use and planning of the management of water resources. Due to the complex terrestrial ecosystem, researchers used to integrate multiple drought indexes for evaluation and monitoring of regional drought conditions. The reviewed composite or aggregated indices revealed that the researchers are mainly focused on regional climatic and environmental conditions, and differences of theoretical backgrounds while integrating a drought index. There is a lack of performance evaluation of these indices because usually the comparative analysis between the integrated index and earlier developed composite indices is not performed. Secondly, the developer researchers did not mention limitations such as data, which is considered a paramount issue while applying these indices in other regions. Therefore, there is still comprehensive work needed for the simple integration of drought indexes for general applications.

Meteorological Drought Monitoring Based on Satellite CHIRPS Product over Gamo Zone, Southern Ethiopia

“…Drought indices are important instruments for defining and monitoring drought because they simplify complex meteorological functions and can quantify climatic abnormalities in terms of severity, length, and frequency [38,39]. Moreover, over the last few decades, many studies have been conducted to monitor the drought in Ethiopia, and most of these studies are SPI-based drought [40,41] analyses based on location-specific observed or stationed rainfall data.…”

Estimating Daily Rice Crop Evapotranspiration in Limited Climatic Data and Utilizing the Soft Computing Algorithms MLP, RBF, GRNN, and GMDH

“…Evapotranspiration is affected by climatological and meteorological factors in a region, such as solar radiation, temperature, humidity, and teleconnection patterns. It is also one of the most important variables in studying dryness stress of the plants and monitoring agricultural drought conditions, which are used in the calculations of drought indices like the Standardized Precipitation-Evapotranspiration Index and Palmer Drought Severity Index [1,2]. erefore, its accurate measurement at the farm level is crucial and necessary for farmers and managers, as well as planners of agricultural water resources.…”

Time series analysis for droughts characteristics response to propagation

“…A shorter time scale (1 month) was selected to calculate the drought duration because at this scale SPI, SSI, and SSMI can capture more drought events than larger timescale. Previous studies mentioned that a larger time scale (e.g., 9–12 months) is sensitive for long drought events (Faiz et al ., 2021; Wu et al ., 2021a). During the analysis, it was found that the duration of M droughts events ranged between 1 and 3 months before the change point in YRB, while after the change point, it showed 2 and 4 months.…”