Comparative analyses of SPI and SPEI as drought assessment tools in Tigray Region, Northern Ethiopia

Abstract

Standard Precipitation Index (SPI) and, its variant, Standard Precipitation and Evapotranspiration Index (SPEI) are among the most commonly used drought assessment indices worldwide. SPI uses precipitation as its only input to assess drought. Unlike SPI, SPEI uses both precipitation and temperature, thereby considering the influence of global warming to some extent. Assessments of performance between SPI and SPEI is well addressed. However, no adequate literature was found on the assessment of the degree of agreement between SPI and SPEI at different time scales. Hence, this research focused on examining the level of agreement between SPI and SPEI as drought assessment tools at 1-month, 3-month, 6-month, 12-month and 24-month time scales. The test of agreement between SPI and SPEI was conducted using Cohen's Kappa statistics and the Bland-Altman method. Gridded monthly precipitation and temperature Climatic Research Unit time-series data version 4.01 were used to calculate SPI and SPEI for the period 1901 to 2016. The results of Cohen's Kappa statistics indicate that there existed a fair degree of agreement between SPI and SPEI at all time scales. A positive linear correlation (r > 0.7, p < 0.001) was also observed between SPI and SPEI ratings at all time scales. Small mean difference (bias) in the Bland and Altman analyses result indicated for the presence of agreement between the assessment tools. This study has found that there is an acceptable level of agreement between SPI and SPEI ratings in the study area, at all timescales.

Meteorological Drought in Northwestern Escarpment of Ethiopian Rift Valley: Detection Seasonal and Spatial Trends

“…Drought is a recurrent natural phenomenon occurs in most parts of the globe, even in the wet and humid regions (Dai, 2011;He et al, 2011;Masih et al, 2014;Tian, 2019;Zarei, 2019). It is one of the natural disasters that extensively damage the environment, and economy in several ways (e.g., agriculture, water resources, ecologies, human welfare and animal life ) ( Mavromatis, 2012;Lu et al, 2015;Tefera & Bello, 2019;Chen et al, 2020;Yacoub & Tayfur, 2020). According to the Emergency Events Database (EM-DAT) (2014), approximately 642 drought events were reported across the globe in the period 1900-2013.…”

“…Moreover, Abrha & Simhadri (2015) conducted a study on climate change and farmers' perception, and factors affecting the perception of climate change in Southern Tigray. Tefera & Bello (2019) also studied the correlation between SPI and SPEI index for drought measurement in Tigray. These authors have used 12 grids for meteorological data analysis throughout the region.…”

“…Agriculture and livestock, which comprise the main livelihood system in the three LZs are frequently affected by drought. This costs thousands of human lives, and brought an adverse effect on the social and economic sectors because it affects signi cantly the smallholder farmers of the area (Abrha & Simhadri, 2015;Tefera & Bello, 2019). According to Gebru & Beyene (2012), the chronic nature of food insecurity leads to not only deprivation of access to immediate food demands, but also to the depletion of assets, which are expended and distress-sold for procuring food from the market or other sources.…”

“…Ethiopia had adopted National Disaster Risk Management Policy and Strategy in 2013 to reduce disaster risks and potentials damages caused by disasters (Drechsler & Soer, 2016 Gidey (2012 and2008) in Tigray Regional State corroborated the presence of locally embedded characters of drought evolution, that needs detail spatial drought studies to provide evidences for policy makers to adopt appropriate local polices to cope up with the risks of drought. Since 2000, drought has become almost a normal phenomenon and most of the year, apart from the rainy seasons, the area is dominated with dry weather and revisited with severe droughts ( Gidey, 2012 ;Gidey et al, 2018aGidey et al, , 2018cGidey et al, , 2018bTefera & Bello, 2019). In the three LZs, the agro-ecosystem is very sensitive for precipitation change.…”

Spectral analysis of drought risk: A case of Bloemfontein, South Africa

“…The four essential types of drought are: meteorological drought, hydrological drought, agricultural drought and socio-economic drought. (i) Meteorological drought is simply the degree of dryness compared to normal conditions and this is irregular over time and certain regions (Olivares Campos, 2016), (ii) hydrological drought on the other hand is deficient rainfall which results into grave reduction in run-off streamflow, inflow into storage reservoirs and revitalizing of groundwater (Orlando Olivares & Zingaretti, 2018), (iii) Agricultural drought refers is a deficit of soil moisture to sustain plants and livestock in that way causing weakened growth and reduced produce (Tefera, Ayoade, & Bello, 2019) and Socio-economic drought is a period in time whereby human activities are negatively affected by reduction in water availability and precipitation. (Praveen et al, 2016).…”