Active Role of the ITCZ and WES Feedback in Hampering the Growth of the Expected Full-Fledged El Niño in 2014

Maeda, Shuhei; Urabe, Yusuke; Takemura, Kazuto; Yasuda, Tohya; Tanimoto, Youichi

doi:10.2151/sola.2016-004

Cited by 12 publications

(7 citation statements)

References 19 publications

(21 reference statements)

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“…Although the weakening of easterly trade wind and the North Pacific high are known as typical response to El Niño event, El Niño conditions were quite weak until the early 2015 and effect of El Niño event on atmospheric circulation fields were also unobvi- ous (Menkes et al 2014;Maeda et al 2016). Therefore, the results presented here suggest that some processes other than ENSO at mid-and/or high latitudes played important roles for the warming in the North Pacific in 2013/14/15.…”

Section: Gasst Variability and Contribution Of The Basinaveraged Sstsmentioning

confidence: 58%

“…In addition, there are meridionally antisymmetric patterns with positive (negative) SLP anomalies in the Northern (Southern) hemisphere around the eastern part of the tropical Pacific. Maeda et al (2016) suggest that feedbacks among wind, evaporation, and SST and intensified convective activity in the intertropical convergence zone contributed to antisymmetric patterns associated with warming in the eastern tropical region in the North Pacific. As a whole, weaker wind anomalies suppress evaporation, and latent heat loss from the ocean is reduced around the extratropics and in the central to eastern tropical region of the North Pacific (Fig.…”

Section: Gasst Variability and Contribution Of The Basinaveraged Sstsmentioning

confidence: 95%

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Rapid Warming in Global Sea Surface Temperature since around 2013

Urabe

Yasuda

Maeda³

2017

SOLA

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Since around 2013, the globally averaged sea surface temperature has rapidly warmed up and reached its highest on record. During this time, there was an intensifying El Niño event that caused positive temperature anomalies in the tropical Pacific Ocean. Compared with the conditions observed in 1997/98, when the previous highest record was marked associated with strong El Niño event, there were notable differences detected in the recent conditions. In the tropical Pacific, remarkable warming near sea surface associated with strong El Niño event in 2015/16 started from significantly warmed conditions along with positive temperature anomaly redistributed from the western part since early 2014, resulting in positive anomalies in the central to eastern part remaining for more than two years, much longer than 1997/98 event. In addition, substantial warming was observed in the North Pacific around 2013 and contribution of the North Pacific region to the global averaged SST anomaly marked significantly large value and was comparable to that of the tropical Pacific.(Citation: Urabe, Y., T. Yasuda, and S. Maeda, 2017: Rapid warming in global sea surface temperature since around 2013. SOLA, 13, 25−30,

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Section: Gasst Variability and Contribution Of The Basinaveraged Sstsmentioning

confidence: 58%

Section: Gasst Variability and Contribution Of The Basinaveraged Sstsmentioning

confidence: 95%

Rapid Warming in Global Sea Surface Temperature since around 2013

Urabe

Yasuda

Maeda³

2017

SOLA

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“…We also analyzed the output of the numerical experiment using a linear baroclinic model (LBM). The experimental design was documented by Maeda et al (2016).…”

Section: Datamentioning

confidence: 99%

“…Meanwhile, equatorially antisymmetric SSTAs with positive (negative) anomalies north (south) of the equator prevailed in the central and eastern tropical Pacific during the summer-fall 2014. Maeda et al (2016) suggested that the intensified evaporative cooling of SST as a result of the prevailing southerly surface wind across the equator contributed to the suppression of the El Niño growth in 2014. They insisted that the wind-evaporation-SST (WES) feedback (Xie and Philander 1994) is the physical background of the surface southerlies in the near-equatorial region and the equatorially antisymmetric SSTAs.…”

Section: Introductionmentioning

confidence: 99%

Significant Atmospheric Circulation Anomalies over the North Pacific Associated with the Enhanced Pacific ITCZ during the Summer–Fall of 2014

Maeda¹,

Urabe

Takemura

et al. 2016

SOLA

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We describe the atmospheric features observed over the North Pacific during the summer-fall of 2014 and investigate their association with the convective activity in the intertropical convergence zone (ITCZ) and underlying oceanic conditions. During this duration, while the NINO.3 index, the area-averaged sea surface temperature anomalies (SSTAs) in the eastern equatorial Pacific, fluctuates around the threshold value for the onset of El Niño events, off-equatorial SSTAs display an equatorial antisymmetric pattern with positive (negative) anomalies north (south) of the equator. As expected from the wind-evaporation-SST feedback, the equatorial antisymmetric SSTAs accompany with anomalous southerlies, converging into a zonal belt of 5°N−10°N that induces enhanced convection in the ITCZ. Thus, the oceanic and atmospheric features in the eastern tropical Pacific are different from those in the typical El Niño events. In contrast, the observed weaker subtropical high and the shallower upper-tropospheric trough over the North Pacific are similar to the features typically found during the El Niño events. The amplitude of those anomalies, however, is much larger than that of regressed anomalies onto the NINO.

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“…This could explain the recent trend in the suppression of warming in the eastern Pacific including the aborted El Niño of 25 2014 (Maeda et al, 2016;Wu et al, 2017) and a decrease in the occurrence of east Pacific-type El Niños. It should also be noted that the El Niño of 2015/16 was one of the largest events; however, it was a mixed type with smaller warming in the eastern Pacific (Paek et al, 2017), as can also be seen in the OLR field in Fig.…”

mentioning

confidence: 95%

Impact of tropical lower stratospheric cooling on deep convective activity: (I) Recent trends in tropical circulation

Kodera

Eguchi

Ueyama

et al. 2018

Preprint

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Abstract. Large changes in tropical circulation, in particular those related to the summer monsoon and cooling of the sea 10 surface in the equatorial eastern Pacific, were noted from the mid to late 1990s. The cause of such recent decadal variations in the tropics was studied by making use of a meteorological reanalysis dataset. Cooling of the equatorial southeastern Pacific Ocean occurred in association with enhanced cross-equatorial southerlies, which resulted from a strengthening and poleward shift of the rising branch of the boreal summer Hadley circulation connected to the stratospheric Brewer-Dobson circulation. From boreal summer to winter, the anomalous convective activity centre moves southward following the 15 seasonal march to the equatorial Indian Ocean-Maritime Continent region, which strengthens the surface easterlies over the equatorial central Pacific. Accordingly, ocean surface cooling extends over the equatorial central Pacific. We suggest that the fundamental factor causing the recent decadal change in the tropical troposphere and the ocean is a poleward shift of the rising branch of the summertime Hadley cell, which can result from a strengthening of extreme deep convection penetrating into the tropical tropopause layer, in particular over the continents of Africa and Asia, and adjacent oceans. We conjecture 20 that this effect is produced by a combination of land surface warming due to increased CO2 and a reduction of static stability in the tropical tropopause layer due to tropical stratospheric cooling.

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Active Role of the ITCZ and WES Feedback in Hampering the Growth of the Expected Full-Fledged El Niño in 2014

Cited by 12 publications

References 19 publications

Rapid Warming in Global Sea Surface Temperature since around 2013

Rapid Warming in Global Sea Surface Temperature since around 2013

Significant Atmospheric Circulation Anomalies over the North Pacific Associated with the Enhanced Pacific ITCZ during the Summer–Fall of 2014

Impact of tropical lower stratospheric cooling on deep convective activity: (I) Recent trends in tropical circulation

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