Analysis of the climate change impact on the spatiotemporal drought in the Gaza region of the southeastern Mediterranean

The anthropogenic climate change impacts, identified by the anomalous disturbances in the spatiotemporal distribution of the rainfall patterns and the increase in the global temperature expected by 1.5–2 °C by the end of the century, are reported by frequent and extreme incidences of drought events where more than 65% of the total world population might endure increasingly periodic drought that is anticipated to double in one-third of the world zones (Cammarano et al. 2019; Hameed et al. 2020; Sardans et al. 2020; IPCC 2022). The climate system in the southeastern Mediterranean region tends to respond quickly to rising levels of global warming in the form of accelerating desertification, decreasing water availability, irreversibly reducing terrestrial biodiversity, and negatively impacting the capacity of the Mediterranean ecosystem to store carbon (Malhi et al. 2021; Vogel et al. 2021). Therefore, the development of drought in the southeast Mediterranean is notably recorded with diverse and inconsistent spatial distribution influenced by the extreme variability of rainfall, the unbalanced seasonal distribution, and the intricate dynamic atmospheric processes (Michaelides et al. 2018). The drought is handled by developing a comparative scale to observe the change in the meteorological time series, such as the Standardized Precipitation Indicator (SPI), which is the most widely used drought index based on changes in precipitation patterns over various periods (McKee et al. 1985, 1993, 1995). The innovative polygon trend analysis (IPTA), a nonparametric technique, is mostly used to analyze drought trends based on rainfall data (Mann 1945; Sen 1968;,Kendall 1975; Ali & Abubaker 2019; Sen et al. 2019; Al-Najjar et al. 2022). However, according to scenarios depicting greenhouse gas concentration and emission, pollutants, and changes in land use, the future patterns of drought are predicted by projecting the atmospheric variables of the future period using General Circulation Models (GCMs) outputs (Sharafati et al. 2020; Salman et al. 2021). Numerous types of research showed the effectiveness of precipitation indices and nonparametric methods for interpreting drought episodes (Ali & Abubaker 2019; Sen et al. 2019; Al-Najjar et al. 2020, 2022; Zhang et al. 2020). Floods, on the other hand, are considered the drought counterpart that results from surplus water conditions of climate change that are statistically analyzed in terms of frequency using the models of cluster analysis such as finite mixture models (Ahani et al. 2020a, 2020b, 2022), hybrid regionalization method (Ahani et al. 2019a, 2019b), feature weighting and selection method (Ahani et al. 2019a, 2019b), feature selection and clustering algorithms (Ahani et al. 2019a, 2019b). Regionally on a local scale, several studies indicate evident signs of drought in the southeastern Mediterranean countries demonstrated by the significant decline in the number of rainy events. The Middle East drought probability increases from less than 20% during the 1970s to more than 80% in the period 2010–2019 (Al-Najjar et al. 2020). Behzadi et al. (2022) used the GCMs projections and SPI to predict the upcoming drought in Iran from 2021 to 2050 where according to the predictions, almost 70% of the future will be dry, and throughout 2030–2040, drought will affect almost all of the country's territories, as well as severe long drought episodes, are addressed to last for 14 years. In Jordan, the annual rate of rainfall drop is evaluated by about 1.8 mm with a drought likelihood of occurring every two to three years (Mustafa & Rahman 2018; Aladaileh et al. 2019). The count of extreme dry days is anticipated to increase twice between 2040 and 2090 in Lebanon (Mahfouz et al. 2016). Syria lives considerable increases in the prevalence and magnitude of droughts, with two severe drought events occurring between the years 1999–2001 and 2007–2010, respectively, which significantly decreased the yields of wheat and barley crops (Mohammed et al. 2020). Drought is a recorded occurrence in Palestine that has an impact on the recharging of the coastal aquifer and the viability of life. The 2007–2008 drought, which resulted in total rainfall that was just 67% of the region's annual average, had a direct negative impact on agricultural productivity, costing 114 million USD, and harmed almost 200,000 different types of cattle (MoA 2008). The likelihood of a drought occurring in Palestine is roughly 60–80% every three months, and it occurs more than 80% of the time each year. The intensity of the drought is growing where the aridity index, which runs from 0.16 to 0.3, is predicted to decline as a result of climate change-related factors like reduced precipitation and rising temperatures. Fiscally, the agricultural industry employs 4.7% of the workforce, whereas fishing employs 10% of the workforce. A greater portion of the workforce is anticipated to lose their jobs due to the drought intensity, especially in the agricultural sector, where the unemployment rate is now over 41% (Al-Najjar et al. 2020). Therefore, focusing on the assessment of the drought induced by rainfall pattern variations in the region of the Gaza Strip to overarch the goal of characterizing the historical drought conditions across the coastal zone of the southeastern Mediterranean using a daily long-term rainfall dataset for the past 48 years (1974–2021) is an urgent issue to deal with the drought episodes alarming and to avoid them in advance the potential drought damages where the study provides the agricultural drought oscillation every 3 months as well as the hydrological drought events every 9–12 months so that to enable the agricultural as well as the coastal aquifer managers for preparing efficient and on time mitigation measures.

The daily rainfall recordings were statistically processed and assembled into sets at each of the nominated meteorological stations to represent the total monthly rainfall. As a result, the trend was examined using Mann–Kendell and Sen slope tests on a monthly and annual basis for the statistical analysis of the rainfall dataset. The Innovative Trend Analysis (ITA) method was used to refine the monthly trend analysis for greater accuracy. The Standardized Precipitation Index (SPI), which measures dryness on a scale of 1, 3, 6, 9, and 12 months, was used to estimate the drought evolving in terms of the agricultural and hydrological dimensions. Hence, the parametric strategy might not be able to identify the trend in the dataset; however, following the nonparametric approach can show a higher potential for the data trend. Accordingly, the SPI is shown to be a useful index for revealing the evolution of a drought event based on a precipitation time series. The index also gives classifications for the severity of the drought, which encourages decision-makers to plan for drought or flood mitigation measures.

The parametric Mann–Kendell and Sen slope tests are tests based on null hypotheticals. According to the null hypothesis, which states that there is no trend, and the alternative hypothesis, which states that there is a significant rising or falling trend in the precipitation, the Mann–Kendell trend test is used to detect statistically significant decreasing and increasing trends in long-term temporal data. Sen's slope is frequently used to determine the sloping trend of the time series. Positive slopes reflect a rising trend, whereas growing slopes are indicated by positive slopes, and zero slope values indicate no trend at all (Mann 1945; Sen 1968; Kendall 1975).

The monthly time scale of the rainfall dataset was divided into two equal portions, and the analysis of the rainfall trends was conducted using the IPTA. The endpoint of the polygon created for each month is formed by plotting the first data set and the second data set on the coordinate x and y axes, respectively. Here, the 45° (1:1) line depicts the non-trend region and divides the area into an upper region with an increasing trend and a lower region with decreasing trend (Sen 2014, 2017). The 3D (dimensional) IPTA, which divides the rainfall time series into three dataset units, is suggested by this study. A deeper assessment of the changes in the rainfall pattern enabling a more precise estimation of the drought patterns from the past to the present over wider subperiods is introduced by the developed 3D-IPTA approach.

In this study, the shifting SPI for the timescales of 3, 6, 9, and 12 months were performed for the daily rainfall dataset at each of the eight stations to detect the frequency pattern of the drought cycles from 1974 through 2021.

Significantly, there is no change detected in the dry months extending from May to August which record a total monthly rainfall of zero at each of the eight meteorological stations. In comparing the prior period of 1998–2021 with the former period of 1974–1997, the wet months of January, October, and December reveal abundant total monthly rainfall at the meteorological stations of Beit Hanon, Beit Lahia, Shati, and Remal. The rainfall data at the metrological station of Nussirat show an incremental rainfall increase in the wet months of October and December while at the remaining stations of Deir Al-Balah, Khanyounis, and Rafah, the increasing trend in the rainfall is detected in January and October. However, the wet months of February, March, April, September, and November show a declining trend at all of the eight meteorological stations.

In general, it can be concluded from Table 3 that the rainfall trend at all of the stations is in a downward pattern from 2006 to 2021, and a drought state dominated during this time.

Table 3

Trend assessment for monsoon months using 3D and 2D IPTA approaches

View Large

Assessing the effects of climate change in Mediterranean regions is crucial to anticipate potential adverse repercussions on agriculture and water supplies. The area of the Gaza Strip forms a representative case study to analyze the climate drought evolution in the Mediterranean region for the reason of its location in between the arid and semiarid zone.

In the southeast Mediterranean region of Gaza, the rainfall patterns throughout 1974–2021 distribute locally over the area with high rainfall intensity in the north decreasing toward the south where the total monthly rainfall ranges between 0 and 445 mm with an average value of between 17 and 32 mm; however, on an annual basis, the total rainfall is between 11 and 877 mm with an average value of between 209 and 381 mm. The monthly trend analysis shows no trend pattern at all of the metrological stations; however, by assessing the annual total rainfall, the trend shows a rising pattern in Beit Hanon and Remal stations while the other stations are experiencing a declining trend and this might be related to the regionalization effects. In this regard, by comparing the former period of 1974–1997 with the posterior period of 1998–2021, a decreasing tendency is observed in February, March, April, and November according to the trend analysis for the rainfall factor during the rainy months over the whole area of the Gaza Strip while January and October typically show a gradual increase in the amount of rainfall. However, the northern part of the Gaza Strip reported an excess of rainfall during December, while the central and southern parts recorded a decline in rainfall. The abundance of rainfall amounts reaches 27% in January and 142% in October, respectively. In December, the north receives a 27% increase, while the south has a −17% reduction. However, the rainfall shortfall over the remaining wet months ranges from −16 to −62%. The incidence of extreme, severe, moderate, and mild droughts per year would be up to 4, 6, 11, and 38% hence the worst drought episodes were detected in 1990, 2010, and 2014.

Based on that, the southeastern Mediterranean region of the Middle East experiences greater precipitation loss than other places, which prolongs the drought in the coastal region due to the influence of the Sinai and the Sahel Desert. The area of the Gaza Strip is vulnerable to drought events with an occurrence incidence of about 59% that potentially affects the agricultural production and the recovery of the Gaza coastal aquifer where according to the reports the year 2010 showed the most significant drought period. The agricultural drought occurs at a maximum of once every 5 years while the hydrological drought occurs every two years; therefore, the northern Gaza Strip has an adequate water balance, which encourages agricultural activity there while forcing other areas to reorganize the irrigation and crop watering schedules.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.