Climate trends and behavior of drought indices: Case study of iraq

The thesis presents a comprehensive study in the investigation of climate change and behavior of aridity and drought in Iraq. The monthly historical data acquired from 28 Meteorological observation stations for the period 1980 – 2011 distributed throughout the Iraq region were utilized. Temporal and spatial changes in total precipitation, maximum, minimum and mean temperatures were analyzed with six trend tests to detect climate change effect on this region. While decreasing trends in precipitation except for two stations while using monthly data was detected, increasing trend was found in temperature series. The North Atlantic Oscillation (NAO) has no detectable influences on temporal patterns of climate data in Iraq. Dry land types and their delineating boundaries and temporal change in aridity conditions were investigated by conventional aridity indices. The spatial variations of aridity indices exhibited that the arid and semi-arid regions cover about 97% of the country areas. As for temporal variations, it was observed that the aridity indices tend to decrease for all stations. The spatial and temporal aridity characteristics were also examined for two periods before and after 1997 to emphasize the influences of abrupt change point year on aridity phenomena. It should be emphasized that the Iraq region like the other Middle East regions was becoming dryer from 1997. The behavior of drought was exhibited by the Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI). The drought analyzes results consistent with the aridity results. The worst dry years were observed after 1997. This study also indicated that the drought and wet situations during September, October and November were related with NAO. The approximately 22% of September drought indices variance was influenced by NAO forcing.