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Modulation of wet-season rainfall over Iran by the Madden– Julian Oscillation, Indian Ocean Dipole and El Niño–Southern Oscillation

Pourasghar, F, Oliver, ECJ ORCID: 0000-0002-4006-2826 and Holbrook, NJ ORCID: 0000-0002-3523-6254 2019 , 'Modulation of wet-season rainfall over Iran by the Madden– Julian Oscillation, Indian Ocean Dipole and El Niño–Southern Oscillation' , International Journal of Climatology , pp. 1-12 , doi: 10.1002/joc.6057.

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Abstract

The intra-seasonal variation of precipitation over Iran is examined in terms of thecombined effects of the Madden–Julian Oscillation (MJO), Indian Ocean Dipole(IOD) and El Niño–Southern Oscillation (ENSO), using daily observations duringthe wet season (October–May) from 1961 to 2015. We have examined how theprobability of daily rainfall above the upper tercile varies across MJO phases duringpositive and negative IOD and ENSO states. The results indicate that theresponse of Iran’s wet-season rainfall to the MJO is affected more by large-scaleatmospheric variations associated with the IOD than by ENSO. The negative (positive)IOD strengthens (suppresses) the MJO–rainfall relationship in the wet and dryMJO phases. The variation in the atmospheric variables (relative humidity and verticalvelocity) indicates more (less) humidity and upwards (downwards) motionwhich increases (decreases) precipitation in wet (dry) MJO phases during the negativeIOD. The rainfall relationship with the MJO during the negative IOD is statisticallysignificant, while the relationship during the positive IOD is weak; and nosignificant relationship is found during either phase of ENSO.

Item Type: Article
Authors/Creators:Pourasghar, F and Oliver, ECJ and Holbrook, NJ
Keywords: Indian Ocean Dipole, intra-seasonal variability, Madden–Julian Oscillation, rainfall probability
Journal or Publication Title: International Journal of Climatology
Publisher: John Wiley & Sons Ltd
ISSN: 0899-8418
DOI / ID Number: 10.1002/joc.6057
Copyright Information:

Copyright 2019 Royal Meteorological Society

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