Assessing the impact of cold and warm ENSO on drought over Iran | ||
| Earth Observation and Geomatics Engineering | ||
| مقاله 5، دوره 2، شماره 1، شهریور 2018، صفحه 45-55 اصل مقاله (1.52 M) | ||
| نوع مقاله: Original Article | ||
| شناسه دیجیتال (DOI): 10.22059/eoge.2018.257714.1022 | ||
| نویسندگان | ||
| Zahir Nikraftar1؛ Ali Sam-Khaniani* 2 | ||
| 1Department of Geomatics Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran | ||
| 2Babol Noshirvani University of Technology, Civil Engineering Department, P.O.Box 484, Shariati Ave, Babol,Mazandaran 47148-71167, Iran | ||
| چکیده | ||
| The impacts of El Niño Southern Oscillation (ENSO) on climate change and in the global scale are well known, and have attracted the attention of researchers since the twentieth century. The study of ENSO impact on climate using precipitation and near surface temperature data from re-analysis products makes global and long-term analyses of this phenomenon possible. The common method to analyze the ENSO impact is to quantify the probability of extreme drought occurrences when the surface temperatures of central-east equatorial Pacific sea are abnormal. Although the results are always uncertain due to the complexity of atmospheric teleconnections, application of the recently available gridded datasets helps one to conduct more precise modeling and predictions. Spatiotemporal patterns of ENSO impact from 1980 to the end of 2013 for four ENSO indices (e.g. Nino 3.4, MEI, ONI, SOI) over Iran was investigated in this study. Spatial maps of the Pearson correlation coefficients and a composite analysis were obtained between the GPCC precipitation and temperature dataset with ENSO states. In addition, the frequency maps of extreme drought conditions during ENSO states were acquired. The results show that the western (along the range of Zagros Mountain) and northern (along the Alborz Mountain and the coastlines of the Caspian Sea to Khorasan Province) regions are more affected by ENSO events. The Pearson correlation coefficient for all four ENSO indices over the mentioned regions was determined to be about 0.70 for precipitation datasets and -0.70 for temperature datasets. The frequency analysis of extreme drought based and CZI (Chinese Z 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 (over the rainy months)/temperature (over the summer months) anomalies, for the El Niño states about +25 (mm)/ -0.5˚ (C) and for the La Niña states about -25 (mm)/+0.6˚ to 1˚ (C). | ||
| کلیدواژهها | ||
| Southern Oscillation Index؛ Climate؛ GPCC datasets؛ Chinese Z Index؛ Teleconnectios؛ Composite analysis | ||
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