Reliability

This study investigates the spatial and temporal variations of the aridity indices to reveal the desertification vulnerability of Iraq region. Relying on temperature and precipitation data taken from 28 meteorological stations for 31 years, the study aims to determine (1) dry land types and their delineating boundaries and (2) temporal change in aridity conditions in Iraq. Lang's aridity (Im), De Martonne's aridity (Am), United Nations Environmental Program (UNEP) aridity (AIu), and Erinç aridity (I E) indices were selected in this study because of the scarcity of the observed data. The analysis of the spatial variation of aridity indices exhibited that the arid and semi-arid regions cover about 97% of the country's areas. As for temporal variations, it was observed that the aridity indices tend to decrease (statistically significant or not) for all stations. The cumulative sum charts (CUSUMs) were applied to detect the year on which the climate pattern of aridity indices had changed from one pattern to another. The abrupt change point was detected around year 1997 for the majority of the stations. Thus, the spatial and temporal aridity characteristics in Iraq were examined for the two periods 1980-1997 and 1998-2011 (before and after the change-point year) to observe the influence of abrupt change point on aridity phenomena. The spatial variation after 1997 was observed from semi-arid (dry sub humid) to arid (semi-arid) especially at the stations located in northern Iraq, while hyper-arid and arid climatic conditions were still dominant over southern and central Iraq. Besides, the negative temporal variations of the two periods 1980-1997 and 1998-2011 were obtained for almost every station. As a result, it was emphasized that Iraq region, like other Middle East regions, has become drier after 1997. The observed reduction in precipitation and increase in temperature for this region seem to make the situation worse in future.

Temporal and spatial changes in Iraq total precipitations, maximum and minimum temperatures in the period of 1980-2011 are analyzed using 28 meteorological stations data distributed throughout the country. The Mann-Kendall and Spearman's Rho test statistics for annual and seasonal Kendall and Sen's T tests for monthly total precipitation and temperature series are calculated and plotted on maps to display any spatial trend patterns. Serial correlation structure in the data series and homogeneity of trends in monthly series were tested before applying the methods. Non-parametric methods using annual and monthly data over 32 years show almost same temporal and spatial patterns in trends of precipitation (P), maximum and minimum temperature (Tmax, Tmin) but some are not statistically significant at the 5 % level. While observation shows decreasing trends in precipitation except for two stations when using monthly data, increasing trend is detected in both temperature series. The Sen's and seasonal Kendall slope estimator are also used to estimate linear trend magnitudes for annual and monthly data to determine the change per unit time in a time series, respectively. The six tests provide the same results about trend in most cases. As a conclusion, all of the study results show that there are not differences in the geographic location of trends (statistically significant or not) in the meteorological variables implying that climatic impacts are spatially uniform in this region. The effect of the North Atlantic Oscillation (NAO) on temporal patterns of climate data in Iraq is also investigated, since it has been suggested that it affects the northern hemisphere climate system. Our study shows that NAO has no detectable influences on climate of this region. This paper is the first comprehensive studies for evidence of climate change with applying tests in this region.

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