Influences of the <scp>MJO</scp> on intraseasonal rainfall variability over southern Iran

Pourasghar, Farnaz; Tozuka, Tomoki; Ghaemi, Hooshang; Oettli, Pascal; Jahanbakhsh, S; Yamagata, Toshio

doi:10.1002/asl2.531

Cited by 19 publications

(22 citation statements)

References 42 publications

(49 reference statements)

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“…Moreover, upwards (downwards) VM is evident in phases 1–2 and 7–8 (3–6) which acts to enhance (suppress) the PR in phases 1–2, 7–8 (3–6). These results are also consistent with previous findings which show that MJO phases 1, 2, 7 and 8 favour positive moisture flux anomalies (i.e., an increase) from the Arabian Sea, the Gulf of Aden and Red Sea being transported northwards and onshore into southern Iran, while phases 3–6 favour offshore (i.e., negative) moisture flux anomalies (Pourasghar et al , ). The offshore moisture flux reduces the moisture supply from southern Iran.…”

Section: Resultssupporting

confidence: 93%

“…Topography and the direction of moisture flux are important to the rainfall distribution during MJO phases over Iran. When the moisture flux is northwards (onshore), the mountainous areas have larger loading in the west to southeast (Zagros Mountains) than the arid region in central and eastern parts of Iran (Pourasghar et al , ).…”

Section: Resultsmentioning

confidence: 99%

“…On intra‐seasonal timescales, the Madden–Julian Oscillation (MJO) is the leading mode of tropical intra‐seasonal variability in the atmosphere. Pourasghar et al () analysed daily precipitation data in the southern part of Iran and showed wet conditions tend to prevail during MJO phases 1, 2, 7 and 8. The geographical position of the mid‐tropospheric trough and high pressure over the Arabian Sea and South Asia are major contributors to the anomalous moisture transport.…”

Section: Introductionmentioning

confidence: 99%

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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

Oliver

Holbrook

2019

Intl Journal of Climatology

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The intra-seasonal variation of precipitation over Iran is examined in terms of the combined effects of the Madden-Julian Oscillation (MJO), Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO), using daily observations during the wet season (October-May) from 1961 to 2015. We have examined how the probability of daily rainfall above the upper tercile varies across MJO phases during positive and negative IOD and ENSO states. The results indicate that the response of Iran's wet-season rainfall to the MJO is affected more by large-scale atmospheric variations associated with the IOD than by ENSO. The negative (positive) IOD strengthens (suppresses) the MJO-rainfall relationship in the wet and dry MJO phases. The variation in the atmospheric variables (relative humidity and vertical velocity) indicates more (less) humidity and upwards (downwards) motion which increases (decreases) precipitation in wet (dry) MJO phases during the negative IOD. The rainfall relationship with the MJO during the negative IOD is statistically significant, while the relationship during the positive IOD is weak; and no significant relationship is found during either phase of ENSO.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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

Oliver

Holbrook

2019

Intl Journal of Climatology

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“…Extreme precipitation and drought over Middle East and Southwest Asia have been reportedly associated with MJO activity (Barlow et al, 2005;Barlow, 2012;Cannon et al, 2017;Hoell et al, 2012;Li et al, 2016;Nazemosadat & Ghaedamini, 2010;Pourasghar et al, 2015). However, MJO is only one of the many modulating factors in the area and no single extreme event can be attributed to MJO activity (Cannon et al, 2017).…”

Section: 1002/2016rg000538mentioning

confidence: 99%

Review of Tropical‐Extratropical Teleconnections on Intraseasonal Time Scales

Stan

Straus

Frederiksen

et al. 2017

Reviews of Geophysics

249

214

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The interactions and teleconnections between the tropical and midlatitude regions on intraseasonal time scales are an important modulator of tropical and extratropical circulation anomalies and their associated weather patterns. These interactions arise due to the impact of the tropics on the extratropics, the impact of the midlatitudes on the tropics, and two‐way interactions between the regions. Observational evidence, as well as theoretical studies with models of complexity ranging from the linear barotropic framework to intricate Earth system models, suggest the involvement of a myriad of processes and mechanisms in generating and maintaining these interconnections. At this stage, our understanding of these teleconnections is primarily a collection of concepts; a comprehensive theoretical framework has yet to be established. These intraseasonal teleconnections are increasingly recognized as an untapped source of potential subseasonal predictability. However, the complexity and diversity of mechanisms associated with these teleconnections, along with the lack of a conceptual framework to relate them, prevent this potential predictability from being translated into realized forecast skill. This review synthesizes our progress in understanding the observed characteristics of intraseasonal tropical‐extratropical interactions and their associated mechanisms, identifies the significant gaps in this understanding, and recommends new research endeavors to address the remaining challenges.

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“…Pohl and Camberlin (2006) concluded that the MJO has a non‐negligible impact on southern African rainfall and atmospheric convection variability. Pourasghar et al (2015) noted the development of more frequently wet conditions over southern Iran during MJO phases 1–2 and 7–8. Sossa et al (2017) showed that the MJO modulates the occurrence of heavy daily precipitation events in West Africa during certain phases.…”

Section: Introductionmentioning

confidence: 99%

On the Link Between the Madden‐Julian Oscillation, Euro‐Mediterranean Weather Regimes, and Morocco Winter Rainfall

et al. 2020

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K-means cluster analysis of wintertime 500-hPa geopotential height anomalies allowed identifying seven weather regimes (WRs) describing the atmospheric variability over the Euro-Mediterranean domain. The study of transitions between those WRs provided consistent results with the westward displacement of the blocking nearby northern Europe before the onset of the negative phase of the North Atlantic Oscillation (NAO−). The onset of the latter is, indeed, preceded by the North Atlantic blocking regime (NABl). In addition, we detected a preferred transition from the Scandinavian Blocking (ScBl) to NAO+ through the European Ridge regime (EuRG), which is modulated by active phases of the Madden-Julian Oscillation (MJO). The examination of the relationship between WRs and precipitation over Morocco showed that the NAO− (NAO+) regime is accompanied by more (less) rainy episodes. The investigation of the lagged relationships between the MJO and the WRs depicted the role of an active MJO in Phase 2 as a precursor of the ScBl and of an active MJO in Phase 6 as a precursor of the NABl. The exploration of the 10-15 days lagged impact of the MJO on Moroccan rainfall showed an increase (decrease) of wet (dry) conditions 10 to 15 days after the occurrence of an active MJO in Phases 6 and 8 (Phases 2-3-4). The MJO modulation of the WRs and rainfall patterns over Morocco constitutes an important source of predictability at the medium-and the extended-range (subseasonal) time scales, with potential use by decision makers in key socioeconomic sectors in the region.

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Influences of the MJO on intraseasonal rainfall variability over southern Iran

Cited by 19 publications

References 42 publications

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

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

Review of Tropical‐Extratropical Teleconnections on Intraseasonal Time Scales

On the Link Between the Madden‐Julian Oscillation, Euro‐Mediterranean Weather Regimes, and Morocco Winter Rainfall

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