Meteorological Drought Analysis in Iraq using SPI and Theory of Runs for the Period 1980-2022

Abstract Iraq, like many other countries in the world, suffers from alternating periods of drought. The aim of this paper is to analyze the meteorological drought in Iraq for the time period 1980-2022, at 27 meteorological stations spread throughout Iraq. Monthly data for precipitation values were collected from the Iraqi Meteorological and Seismological Organization (IMOS). The monthly time series contained missing data that were compensated by the normal ratio (NR) and the multiple linear regression (MLR) methods. To compare the two methods and evaluate the results of filling for missing data, statistical tests were used. The homogeneity test, the Mann-Kendall test, and the consistency test were used to determine the accuracy of rainfall data records and to know the trend of climate data and how its homogeneity. To estimate drought values, the Standard Precipitation Index (SPI) was used for 12-month time scale, and the theory of runs was used to analyze the characteristics of meteorological drought, such as its duration, intensity, and amount of rain deficit. The results of the statistical tests showed that the (NR) method is more accurate and reliable and gives the best results with less errors after examining it with six statistical indicators than the (MLR) method. The results of the homogeneity tests showed that all stations were consistent and homogeneous, except for the Haditha station, which failed two tests and its data was corrected using double mass curve method, so it became homogeneous. The results of the Mann-Kendall test showed that all stations recorded a decrease in average rainfall values during the study period, except for the stations in Baghdad, Erbil, and Salahaddin, and it was most severe in the northern stations such as Sulaymaniyah, Khanaqin, Kirkuk, Mosul, Zakho, and Tal-Afar. The SPI results showed that Iraq faced repeated and successive periods of drought, which covered 45% of the study area for the years (1998-2001), 41% for the years (2008-2011), and 14% for the years (2015-2017), and were most severe in the northern stations where drought severity reached the maximum at Salahaddin station which recorded a rainfall deficit of 396.95 mm/year. The Amara and Samawa stations suffered from repeated short and long-term drought periods 18 times during the study period.