1- Department of Geographical, Faculty of Literature and Humanities, University of Lorestan, Khorramabad, Iran.
2- Department of Geographical, Faculty of Literature and Humanities, University of Lorestan, Khorramabad, Iran. ,d.yarahmadi@gmail.com
2- Department of Geographical, Faculty of Literature and Humanities, University of Lorestan, Khorramabad, Iran. ,
Abstract: (108 Views)
The ENSO phenomenon is considered one of the most important interannual oscillations in the Earth–atmosphere system and plays a significant role in precipitation variability across different regions of the world. In this study, to identify the multiscale relationship between different ENSO phases and monthly precipitation variability in Iraq, the monthly Niño3.4 index, the Maximum Overlap Discrete Wavelet Transform (MODWT), and the Continuous Morlet Wavelet Transform were employed. First, using multiresolution decomposition of the monthly precipitation signal from 16 stations across Iraq (1990-2020) into six (6) frequency levels (from monthly to multi-year scales), it was revealed that the precipitation signals at all stations follow a relatively similar pattern, although with different oscillation amplitudes. The amplitude of precipitation fluctuations at monthly and seasonal scales was found to be stronger at northern and foothill stations (Kirkuk, Mosul, and Khanaqin) compared to other regions of Iraq, indicating a shorter transition between wet and dry months in northern Iraq. Furthermore, the overall trend of the A6 component at all stations exhibited a decreasing pattern during 1995–2010, with this downward trend being more pronounced in the central and southern regions than in the north. The results of correlation analysis and multiscale wavelet coherence demonstrated a positive and multiscale relationship between ENSO and monthly precipitation in Iraq. Surrogate significance testing indicated that this relationship is not significant at wavelet levels 1 to 3 but becomes significant at 1.5–3-year and 2.5–5.5-year scales (wavelet levels 4 and 5). Overall, precipitation in Iraq tends to increase during El Niño (warm ENSO phase) events and decrease during La Niña (cold ENSO phase) events.
Type of Study: Research |
Subject:
climatology
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