This study aims to investigate the standardized precipitation evapotranspiration index (SPEI) using the monthly observed and gridded Climate Research Unit (CRU) dataset across 13 stations in Ethiopia during the period 1970–2005. SPEI is computed at a 4-month timescale to represent drought during the Belg (February–May) and Kirmet (June–September) seasons separately, and at an 8-month timescale to represent the drought during these two seasons together (February–September). The results show that there are extremely strong correlations (R ≥ 0.8) between the estimated precipitation values from CRU and the observed values, with root mean square error (RMSE) of 4–99 mm and mean percentage error (MPE%) of −30 to 73% at most stations. For temperature and SPEI, the CRU shows almost strong correlations (0.6 ≤ R < 0.8), while the dominant values of RMSE and MPE are 0.7–5 °C and −22 to 26%, respectively, for temperature and 0.28–0.96 and −49 to 55%, respectively, for SPEI during the three seasons. It is also found that each of the SPEI clusters (dry, normal, and wet) estimated from CRU has a high success percentage (≥ 60%) at more than 50% of the stations, while the general accuracy exceeds 60% for the three SPEI clusters together at more than 75% of the stations. Finally, the correct hits for the estimated SPEI clusters from CRU are often within the corresponding observed cluster but may shift into another category (extreme, severe, and moderate) except for a few events.

This study aims to assess the impact of using different fuels in Egyptian Titan Alexandria Portland Cement Company on emissions and concentrations of pollutants (Total suspended particles (TSP), nitrogen dioxide (NO₂‎), and sulfur dioxide (SO₂)) and their influence on ambient air quality during the period 2014–2020 using AERMOD dispersion model. The results showed that changing the fuel from natural gas in 2014 to coal mixed with alternative fuels (Tire-Derived Fuel (TDF), Dried Sewage Sludge (DSS), and Refuse Derived Fuels (RDF)) in 2015–2020 caused fluctuating variations in pollutant emissions and concentrations. The highest and lowest maximum concentrations of TSP occurred in 2017 and 2014 respectively, where the TSP is positively correlated with coal, RDF, and DSS and negatively correlated with natural gas, diesel, and TDF. Also, the lowest and highest maximum NO₂ concentrations were detected in 2020 and 2016 followed by 2017 respectively, where NO₂ is positively correlated with DSS and negatively correlated with TDF and varies with diesel, coal, and RDF. Moreover, the maximum concentrations of SO₂ were the lowest in 2018 and highest in 2016 followed by 2017 because of its considerable positive correlation with natural gas and DSS and negative correlation with RDF, TDF, and coal. Generally, it was found that increasing the percentage of TDF and RDF with decreasing the percentage of DSS, diesel, and coal will reduce pollutant emissions and concentrations and enhance ambient air quality.