Heavy precipitation in the southwest of Iran: association with the Madden–Julian Oscillation and synoptic scale analysis

Nazemosadat, M. J.; Shahgholian, Kokab

doi:10.1007/s00382-016-3496-6

Cited by 19 publications

(16 citation statements)

References 34 publications

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“…The mean and anomaly values of the 200 hPa vector wind for the SWPP and SWWD are shown in Figure 5a,b, respectively. The presented mean‐flow is known as the Middle Eastern jet stream (Barlow et al ., 2005; Nazemosadat and Shahgholian, 2017). Compared to SWWD, wind speed over the study area is greater for the SWPP, and their difference reaches to about 15 ms −1 over the jet streak region.…”

Section: Resultsmentioning

confidence: 99%

“…A number of investigators have reported that for southwestern districts of Iran, precipitation amount and the frequency of wet spells are meaningfully greater for the MJO phases 7, 8, 1, and 2 (wet phases), as compared to phases 3 to 6 (dry phases) (Barlow et al ., 2005; Nazemosadat and Ghaedamini, 2010; Pourasghar et al ., 2015; Nazemosadat and Shahgholian, 2017). However, there are numerous episodes within these wet phases, for which the precipitation is zero over most of the study area.…”

Section: Introductionmentioning

confidence: 99%

“…The oscillation has a remarkable influence on climate variability in Southwest Asia, including most parts of Iran (Barlow et al, 2002(Barlow et al, , 2005Nazemosadat and Ghaedamini, 2010;Hoell et al, 2012Hoell et al, , 2015Hoell et al, , 2016Hoell et al, , 2018Hoell and Funk, 2013;Nazemosadat and Shahgholian, 2017). Analyses of daily observations have shown that precipitation over Southwest Asia during the cold months of the year is modulated by the MJO activities with a strength that is comparable to the inter-annual variability (Barlow et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Introducing new climate indices for identifying wet/dry spells within an Madden‐Julian Oscillation phase

Nazemosadat

Shahgholian

Ghaedamini

et al. 2020

Intl Journal of Climatology

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Daily values of precipitation in southwestern parts of Iran along with the corresponding Madden-Julian oscillation (MJO) phase are analysed to introduce some auxiliary indicators that can identify the wet and dry spells within a particular MJO phase. As a case study, the identification procedure focuses on phase 1 during the rainy season (Nov-Apr). The study shows that this phase contains two opposite spells, referred to as spells with pervasive precipitation (SWPP) and spells with widespread dryness (SWWD). Although the precipitation characteristics are essentially different between SWPP and SWWD, their associated MJO indices are found statistically identical. Therefore, the MJOprecipitation relationship fails to identify the wet/dry spells within an MJO phase. To resolve this deficiency, other climate indicators, which behave differently between these two spells, are introduced. The westward moisture flux over equatorial parts of the Indian Ocean and the northeastward moisture flux over the North African tropics are up to seven times stronger in the SWPP compared to SWWD. The dominance of a strong cyclonic (anticyclonic) circulation over the eastern side of the Mediterranean Sea and the negative (positive) west-east temperature gradient over southern parts of Iran are introduced as SWPP (SWWD) indicators. The study reveals that the SWPP (SWWD) coincides with a strong (weak) convection dipole that resembles the positive Indian Ocean dipole. The intensified (weakened) wind speed in the subtropical jet stream and persistence of the jet-exit-regions above Iran (Egypt and Saudi Arabia) are other SWPP (SWWD) indicators. Negative (positive) anomalies of sea surface temperature over the North Atlantic Ocean, the Black, Mediterranean, and Caspian Seas, as well as the Persian Gulf, signify the prevalence of the SWPP (SWWD). To the best of our knowledge, this is the first time that auxiliary indices are utilized to improve the MJO-precipitation relationship in southwestern Iran.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Introducing new climate indices for identifying wet/dry spells within an Madden‐Julian Oscillation phase

Nazemosadat

Shahgholian

Ghaedamini

et al. 2020

Intl Journal of Climatology

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“…Vertical velocity anomalies also vary with the eastwards propagation of the MJO. Nazemosadat and Shahgholian () analysed characteristics of heavy precipitation in south western Iran and its linkage to the MJO. The highest frequency of heavy precipitation is related to MJO phase 8.…”

Section: Introductionmentioning

confidence: 99%

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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“…The EA‐WA sector has been previously identified as being a region where precipitation can be forecast with higher skill compared to most places of the globe on the subseasonal time scale (Tippett et al, ; Vigaud et al, ). Enhanced probabilities of above‐normal rainfall in Week 3–4 forecasts (i.e., 15–28 days in advance) for starts during El Niño and MJO Phase 7 are consistent with regional influences from ENSO (Abid et al, ; Alizadeh‐Choobari et al, ; Atif et al, ; Barlow et al, ; Hoell et al, ; Hoell, Barlow, Cannon, & Xu, ; Kang et al, ; Kijazi and Reason, ; Mutai and Ward, ; Nicholson, ; Soltani et al, ; Rana et al, , ) and the MJO (Barlow et al, , ; Hoell et al, ; Hoell, Cannon, & Barlow, ; Mutai and Ward, ; Pohl and Camberlin, , ; Pohl et al, ; Nazemosadat and Ghaedamini, ; Nazemosadat and Shahgholian, ). As noted in the recent review from Barlow et al (), regional droughts have also been related to ENSO (Al Senafi and Anis, ; Athar, ; Barlow et al, ; Donat et al, ; Hoell et al, , , ; Krichak et al, ; Mariotti et al, ; Mariotti, ; Nazemosadat and Ghasemi, ; Niranjan and Ouarda, ; Price et al, ; Syed et al, ; Yin et al, ) and the MJO (Barlow et al, ; Barlow, ; Hoell et al, ; Nazemosadat and Ghaedamini, ; Pourasghar et al, ; Tippett et al, ).…”

Section: Introductionmentioning

confidence: 54%

Deterministic Skill of Subseasonal Precipitation Forecasts for the East Africa‐West Asia Sector from September to May

Vigaud¹,

Tippett

Robertson³

2019

JGR Atmospheres

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The East Africa-West Asia (EA-WA) sector is a region where the skill in forecasting rainfall is unusually high in the subseasonal-to-seasonal (S2S) time range and where ENSO and MJO signals have significant impacts. Much of regional rainfall intra-seasonal variability is related to tropical-temperate interactions on synoptic time scales, and we examine whether the skill of dynamical S2S forecasts for the region exceeds the predictability associated with ENSO and the MJO. Deterministic skill (Spearman's rank correlation) of multimodel ensemble forecasts of weekly and Week 3-4 precipitation averages is examined for starts in September-April, based on three ensemble prediction systems (EPS) from the S2S prediction project over the common 1999-2010 reforecasts period. The skill of weekly forecasts decreases with increasing lead but remains statistically significant out to Week 3 and Week 4, a level of skill that has not been previously reported at such leads. The skill of Week 3-4 forecasts is higher than that of Week 3 or Week 4 forecasts. The prediction skill of weekly and 2-week precipitation averages from ENSO and the MJO is estimated using a multiple linear regression and found to be less than that achieved by the dynamical forecasts for Week 3, Week 4, and Week 3-4 targets. This is evidence for achievable forecast skill that extends beyond typical weather-scale lead times and that is not simply related to ENSO or MJO signals. The opportunity for skillful predictions is illustrated through successful forecasts up to 4 weeks in advance of extreme rainfall over the Arabian peninsula related to strong tropical-temperate interactions during weak ENSO and MJO conditions.

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Heavy precipitation in the southwest of Iran: association with the Madden–Julian Oscillation and synoptic scale analysis

Cited by 19 publications

References 34 publications

Introducing new climate indices for identifying wet/dry spells within an Madden‐Julian Oscillation phase

Introducing new climate indices for identifying wet/dry spells within an Madden‐Julian Oscillation phase

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

Deterministic Skill of Subseasonal Precipitation Forecasts for the East Africa‐West Asia Sector from September to May

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