Assessing the impact of cold and warm ENSO on drought over Iran

Abstract

<span>The impacts of El Niño Southern Oscillation (ENSO) on climate change and in the global scale are well<br /><span>known, and have attracted the attention of researchers since the twentieth century. The study of ENSO<br /><span>impact on climate using precipitation and near surface temperature data from re-analysis products makes<br /><span>global and long-term analyses of this phenomenon possible. The common method to analyze the ENSO<br /><span>impact is to quantify the probability of extreme drought occurrences when the surface temperatures of<br /><span>central-east equatorial Pacific sea are abnormal. Although the results are always uncertain due to the<br /><span>complexity of atmospheric teleconnections, application of the recently available gridded datasets helps one<br /><span>to conduct more precise modeling and predictions. Spatiotemporal patterns of ENSO impact from 1980 to<br /><span>the end of 2013 for four ENSO indices (e.g. Nino 3.4, MEI, ONI, SOI) over Iran was investigated in this<br /><span>study. Spatial maps of the Pearson correlation coefficients and a composite analysis were obtained between<br /><span>the GPCC precipitation and temperature dataset with ENSO states. In addition, the frequency maps of<br /><span>extreme drought conditions during ENSO states were acquired. The results show that the western (along the<br /><span>range of Zagros Mountain) and northern (along the Alborz Mountain and the coastlines of the Caspian Sea<br /><span>to Khorasan Province) regions are more affected by ENSO events. The Pearson correlation coefficient for<br /><span>all four ENSO indices over the mentioned regions was determined to be about 0.70 for precipitation datasets<br /><span>and -0.70 for temperature datasets. The frequency analysis of extreme drought based and CZI (Chinese Z<br /><span>Index) and ENSO phases shows that the western and northeast parts of Iran are more affected by centraleast equatorial Pacific teleconnections. Composite analysis for all four ENSO indices shows the precipitation<br /><span>(over the rainy months)/temperature (over the summer months) anomalies, for the El Niño states about +25<br /><span>(mm)/ -0.5˚ (C) and for the La Niña states about -25 (mm)/+0.6˚ to 1˚ (C).</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span><br /></span>