Impacts of canonical and Modoki El Niño on tropical Atlantic SST

May combine two claims.

Rodrigues et al. [2011] did show significantly more warming in the tropical North Atlantic in boreal winter and spring for canonical relative to Modoki, which is consistent with our results.

“Rodrigues et al. [2011] did show significantly more warming in the tropical North Atlantic in boreal winter and spring for canonical relative to Modoki, which is consistent with our results.”

• cites Rodrigues et al. [2011] sourcePartly supported

  Section 3 (‘Atlantic and Pacific SST variability’; page unavailable) reports greater tropical North Atlantic warming in boreal spring for DRY events, whose Pacific warming peaks in the east, than for WET events, whose warming peaks in the central Pacific. But it explicitly says the observed winter difference was not statistically significant. ‘The crucial role of ocean dynamics’ further limits the statistically significant spring difference to the MICOM simulation, so the unqualified claim of significant warming in both seasons overstates the paper. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Fluctuations in the tropical Atlantic north-south SST gradient (i.e., the Meridional Mode) have been linked to hurricane activity and to changes in rainfall over Africa and South America.

“In addition, fluctuations in the tropical Atlantic north-south SST gradient (i.e., the Meridional Mode) have been linked to hurricane activity and to changes in rainfall over Africa and South America [Kossin and Vimont, 2007;Hastenrath and Heller, 1977].”

• cites Kossin and Vimont, 2007 sourcePartly supported

  The ‘Atlantic Meridional Mode’ section identifies a meridional SST gradient as a feature of the mode and links it to hurricane variability and rainfall variations in the Sahel region of West Africa. The passages do not establish the claimed link to rainfall changes in South America (page numbers unavailable). (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites Hastenrath and Heller, 1977 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The differences in the equatorial and tropical South Atlantic may stem from differences in the time period analyzed (1957-2002 in Rodrigues et al. [2011] compared to 1880-2010 in the present study) and the compositing technique (Rodrigues et al. [2011] based their composites on Northeast Brazil rainfall).

“The differences in the equatorial and tropical South Atlantic may stem from differences in the time period analyzed (1957( -2002( in Rodrigues et al. [2011] ] compared to 1880-2010 in the present study) and the compositing technique (Rodrigues et al. [2011] based their composites on Northeast Brazil rainfall).”

• cites Rodrigues et al. [2011] sourceSupported

May combine two claims.

El Niño Modoki induces significant cooling in the northeastern tropical Atlantic and near-neutral conditions elsewhere in the tropical Atlantic.

“El Niño Modoki instead induces significant cooling in the northeastern tropical Atlantic and near-neutral conditions elsewhere in the tropical Atlantic.”

• Also stated in: § 3. Results · plain

  “Instead, there are near-neutral SST anomalies in the northwestern, equatorial, and southeastern tropical Atlantic and anomalous cooling in the eastern tropical North Atlantic.”

May combine two claims.

Canonical El Niño produces significant warming in the tropical North Atlantic, building in boreal winter and peaking during March-May.

“For canonical events, anomalous warming builds up in boreal winter and peaks across the tropical North Atlantic basin during March-May (Figures 2a and 2b).”

Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based). The quote only partly states this claim.

The below-average heights over the southeastern United States are consistent with the anomalous southwesterly surface winds observed in the tropical North Atlantic during January-March for canonical events.

“surface winds we observe in the tropical North Atlantic during January-March for canonical events (Figure 2b).”

May combine two claims.

During the following boreal fall (SON) the most significant SST anomalies in the tropical Atlantic for canonical El Niño relative to Modoki continue to shift southwestward (15 N-30 N, 45 W-75 W), possibly due to a positive wind-evaporation-SST feedback.

“During the following boreal fall (SON) the most significant SST anomalies in the tropical Atlantic for canonical El Niño relative to Modoki continue to shift southwestward ($15 N-30 N, 45 W-75 W), possibly due to a positive wind-evaporation-SST feedback (Figure 5d) [Smirnov and Vimont, 2012].”

• cites Smirnov and Vimont, 2012 sourceNot checked — no full text of the source

May combine two claims.

The negative SST anomalies propagate southwestward and peak during spring and summer, covering the region 15 N-35 N, 15 W-40 W.

“The negative SST anomalies propagate southwestward and peak during the spring and summer, covering the region 15 N-35 N, 15 W-40 W (Figure 3c).”

May combine two claims.

During October-December, canonical events drive anomalously southwesterly winds between 20 N and 35 N, relative to Modoki, weakening the mean northeasterly trade winds, reducing evaporative cooling, and warming SSTs.

“During October-December (two months prior to the boreal winter season), canonical events drive anomalously southwesterly winds between 20 N and 35 N, relative to Modoki (Figures 2 and 3), weakening the mean northeasterly trade winds, reducing evaporative cooling, and warming SSTs (Figure 5a).”

May combine two claims.

Modoki forces a similar Kelvin wave response, though the signal is weaker, especially for tropospheric temperature.

“Modoki forces a similar Kelvin wave response, though the signal is weaker, especially for tropospheric temperature, consistent with Larson et al. [2012].”

• cites Larson et al. [2012] sourceNot checked — no full text of the source

May combine two claims.

This drives significantly more anomalous warming of the tropical North Atlantic (about 0-25 N, 20 W-60 W) for canonical events relative to Modoki events during boreal spring, with peak warming shifted southward to about 5 N-15 N, 20 W-30 W.

“Ultimately, this drives significantly more anomalous warming of the tropical North Atlantic (about 0 -25 N, 20 W-60 W) for canonical events relative to Modoki events during boreal spring, and the peak warming is shifted southward to about 5 N-15 N, 20 W-30 W during this season.”

May combine two claims.

Southwesterly surface wind anomalies spread and intensify during January-March leading up to boreal spring, driving weaker northeasterly trade winds and less evaporative cooling across the basin.

“Southwesterly surface wind anomalies spread and intensify during January-March leading up to the boreal spring season, driving weaker northeasterly trade winds and less evaporative cooling across the basin (Figure 5b).”

May combine two claims.

Heights are significantly above normal in the North Atlantic around 30 N-45 N, 25 W-75 W for Modoki, reminiscent of a positive phase of the North Atlantic Oscillation.

“In addition, heights are significantly above normal in the North Atlantic around 30 N-45 N, 25 W-75 W for Modoki, reminiscent of a positive phase of the North Atlantic Oscillation [Barnston and Livezey, 1987].”

• cites Barnston and Livezey, 1987Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

In October-December, the canonical composite of 500 mb height shows an anomalous deepening of the Aleutian Low, consistent with the development of a positive PNA pattern, and above-average heights extending from 30 S to 30 N in the tropical Atlantic.

“In October-December, the canonical composite of 500 mb height shows an anomalous deepening of the Aleutian Low, consistent with the development of a positive PNA pattern, and above-average heights extending from 30 S to 30 N in the tropical Atlantic (Figure 6a).”

May combine two claims.

The canonical-Modoki differences reveal the greater intensity and more extensive eastward propagation of the tropospheric temperature anomalies for canonical relative to Modoki.

“The canonical-Modoki differences reveal the greater intensity and more extensive eastward propagation of the tropospheric temperature anomalies for canonical relative to Modoki (Figure 6f).”

The quote only partly states this claim.

The reductions in wind speed in JFM for the EMI, TNI, and PMM indices are all significant at the 10% level.

“EMI, TNI, and PMM indices are all significant at the 10% level.”

May combine two claims.

Surface winds converge anomalously during boreal winter, consistent with anomalous eastward shifts of deep convection and the rising branch of the Walker Circulation.

“Surface winds also converge anomalously during boreal winter, consistent with anomalous eastward shifts of deep convection and the rising branch of the Walker Circulation [Bjerknes, 1969].”

• cites Bjerknes, 1969Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Similar reductions in wind speed can be seen in the Niño-4 Index, though the statistical significance is not as high.

“Similar reductions in wind speed can be seen in the Niño-4 Index, though the statistical significance is not as high.”

May combine two claims.

The values for October-December and April-June are also positive, with canonical minus noncanonical differences ranging from 0.13 to 0.20 K and significance varying from 5% to 20%.

“The values for October-December (leading boreal winter by 2 months) and April-June (leading boreal summer by 2 months) are also positive, with canonical minus noncanonical differences ranging from 0.13 to 0.20 K and significance varying from 5% to 20%.”

May combine two claims.

The canonical and Modoki El Niños peak in boreal winter, with the warmest SST anomalies concentrated in the East Pacific for canonical and near the dateline for Modoki.

“The canonical and Modoki El Niños peak in boreal winter, with the warmest SST anomalies concentrated in the East Pacific for canonical and near the dateline for Modoki.”

May combine two claims.

The canonical-Modoki difference closely mirrors the canonical composite, with lower heights in the subtropical North Atlantic and Gulf of Mexico (25 N-45 N, 45 W-120 W) and a northwest to southeast gradient of height across the tropical North Atlantic.

“As a result, the canonical-Modoki difference closely mirrors the canonical composite, with lower heights in the subtropical North Atlantic and Gulf of Mexico (25 N-45 N, 45 W-120 W) and a northwest to southeast gradient of height across the tropical North Atlantic (Figure 6f).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Composites of SST anomalies in the tropical Pacific from the DJF peak of a canonical or Modoki event until the following JJA generally agree with previous results.

“Composites of SST anomalies in the tropical Pacific from the boreal winter (DJF) peak of a canonical or Modoki event until the boreal summer (JJA) after the peak of the event generally agree with previous results (Figure 1).”

May combine two claims.

The difference of canonical relative to Modoki shows an anomalously low height signal in the North Atlantic and an anomalously high height signal in the eastern tropical North Atlantic.

“As a result, the difference of canonical relative to Modoki shows an anomalously low height signal in the North Atlantic and an anomalously high height signal in the eastern tropical North Atlantic (Figure 6c).”

May combine two claims.

In January-March, the composite of canonical events clearly shows the classic PNA pattern, with a deepened Aleutian Low, above-average heights over northern North America, and below-average heights over the southeastern United States.

“In January-March, two months prior to the boral spring season (MAM), the composite of canonical events clearly shows the classic PNA pattern, with a deepened Aleutian Low, above-average heights over northern North America, and below-average heights over the southeastern United States.”

May combine two claims.

In boreal winter the entire tropical Atlantic from 15 S to 30 N is anomalously warm, with the most significant anomalies extending across the tropical North Atlantic basin between about 15 N and 30 N and 25 W and 60 W.

“In boreal winter the entire tropical Atlantic from 15 S to 30 N is anomalously warm, with the most significant anomalies extending across the tropical North Atlantic basin between about 15 N and 30 N and 25 W and 60 W.”

May combine two claims.

There are also positive anomalies of surface solar radiation during this season that may contribute to the observed warming for canonical relative to Modoki, though the anomalies are confined mainly to the central tropical North Atlantic (30 W-50 W, 10 N-20 N).

“There are also positive anomalies of surface solar radiation during this season that may contribute to the observed warming for canonical relative to Modoki, though the anomalies are confined mainly to the central tropical North Atlantic (30 W-50 W, 10 N-20 N; not shown).”

May combine two claims.

Results indicate a significant southeastward height gradient across the tropical North Atlantic during January-March that is consistent across all noncanonical indices except CPW.

“Results indicate a significant southeastward height gradient across the tropical North Atlantic during January-March (Table 2) that is consistent across all noncanonical indices except CPW.”

May combine two claims.

Atmospheric Kelvin waves warm the troposphere over the tropical Atlantic anomalously, increasing static stability.

“Atmospheric Kelvin waves warm the troposphere over the tropical Atlantic anomalously, increasing static stability [e.g., Chiang and Sobel, 2002;Lee et al., 2011].”

• cites Chiang and Sobel, 2002Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Lee et al., 2011Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Strong El Niño events are linked to a strengthening of the PNA pattern, including a deepening of the Aleutian Low, above-average heights over the intermountain region of North America, and below-average heights over the southeastern United States.

“Strong El Niño events have been linked to a strengthening of the Pacific/North American (PNA) pattern, namely a deepening of the Aleutian Low, above-average heights over the intermountain region of North America, and below-average heights over the southeastern United States [Wallace and Gutzler, 1981].”

• cites Wallace and Gutzler, 1981Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The Kelvin wave propagates eastward over South America to the tropical Atlantic and may force a stationary baroclinic Rossby wave.

“The Kelvin wave propagates eastward over South America to the tropical Atlantic and may force a stationary baroclinic Rossby wave, depicted in Gill's [1980] model of tropical atmospheric circulations.”

• cites Gill, 1980 sourceNot checked — no full text of the source

May combine two claims.

The combination of midlatitude and equatorial teleconnections tends to weaken the northeasterly trade winds in the tropical North Atlantic, reducing evaporative cooling and increasing SST.

“The combination of midlatitude and equatorial teleconnections tends to weaken the northeasterly trade winds in the tropical North Atlantic, reducing evaporative cooling of the ocean's surface and increasing SST [Carton et al., 1996;Enfield and Mayer, 1997].”

• cites Carton et al., 1996 sourceNot checked — no full text of the source
• cites Enfield and Mayer, 1997 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

During a Modoki El Niño, warm SST anomalies are often accompanied by anomalously cold SSTs to the east and west, forming a distinctive horseshoe pattern.

“During a Modoki El Niño, warm SST anomalies are often accompanied by anomalously cold SSTs to the east and west, forming a distinctive horseshoe pattern [Ashok et al., 2007].”

• cites Ashok et al., 2007 sourceNot checked — no full text of the source

May combine two claims.

Surface winds drive SST variability in the tropical Atlantic, with winds leading by about 2 months.

“Surface winds drive SST variability in the tropical Atlantic, with winds leading by about 2 months [Carton et al., 1996;Czaja et al., 2002].”

• cites Carton et al., 1996 sourceNot checked — no full text of the source
• cites Czaja et al., 2002Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Classified as probably not a substantial claim.

A low threshold of 0.5 standard deviations for defining canonical El Niño events was chosen to increase sample size and statistical robustness.

“This low threshold was chosen in order to increase the sample size and hence the statistical robustness of our results.”

May combine two claims.

A lack of anomalous surface wind forcing allows warm SST anomalies to weaken in summer and diminish further by the following fall.

“A lack of anomalous surface wind forcing allows warm SST anomalies to weaken in the summer and diminish further by the following fall (SON) (Figures 2c and 2d).”

May combine two claims.

These two height anomalies are consistent with the anomalous southwesterly surface winds observed in October-December, which act to weaken the northeasterly trade winds, reduce evaporative cooling, and increase SST for canonical relative to Modoki, near 15 N-30 N, 20 W-60 W and during December-February.

“These two height anomalies are consistent with the anomalous southwesterly surface winds observed in October-December, which act to weaken the northeasterly trade winds, reduce evaporative cooling, and increase SST for canonical relative to Modoki, near 15 N-30 N, 20 W-60 W and during December-February (Figures 2, 3, and 5a).”

May combine two claims.

The main mechanisms through which El Niño influences the tropical Atlantic are the indirect, midlatitude PNA pattern and the more direct equatorial atmospheric Kelvin wave response.

“The main mechanisms through which El Niño influences the tropical Atlantic are the indirect, midlatitude PNA pattern and the more direct equatorial atmospheric Kelvin wave response.”

Classified as probably not a substantial claim.

Common years between canonical and Modoki events are omitted from the composites to isolate the signal associated with each index.

“In order to isolate the signal associated with each index, common years between canonical and Modoki events are omitted from the composites.”

May combine two claims.

The enhanced wind speed drives an anomalous increase in evaporation and anomalously cold SSTs in boreal winter (DJF), 2 months later.

“The enhanced wind speed drives an anomalous increase in evaporation and anomalously cold SSTs in boreal winter (DJF), 2 months later.”

May combine two claims.

The weakening and southwestward shift of the SST difference signal in boreal summer is consistent with very weak anomalies of surface winds two months prior to the summer season (April-June) for canonical and Modoki and the tendency for SST anomalies in the tropical North Atlantic to propagate southwestward due to positive wind-evaporation-SST feedback.

“The weakening and southwestward shift of the SST difference signal in boreal summer is also consistent with very weak anomalies of surface winds two months prior to the summer season (April-June) for canonical and Modoki and the tendency for SST anomalies in the tropical North Atlantic to propagate southwestward due to positive wind-evaporation-SST feedback [e.g., Vimont, 2010].”

• cites Vimont, 2010 sourceNot checked — no full text of the source

Classified as probably not a substantial claim.

The equatorial atmospheric Kelvin wave propagates rapidly eastward after the initial forcing.

“The equatorial, atmospheric Kelvin wave propagates rapidly eastward after the initial forcing [e.g., Chiang and Sobel, 2002].”

• cites Chiang and Sobel, 2002Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Ultimately the PNA pattern, atmospheric Kelvin wave, and the baroclinic Rossby wave combine to force weaker northeasterly trade winds in January-March (resulting in less evaporative cooling) and the warm SSTs observed for canonical relative to Modoki between 0 N and 30 N and 25 W and 60 W during March-May.

“Ultimately the PNA pattern, atmospheric Kelvin wave, and the baroclinic Rossby wave combine to force weaker northeasterly trade winds in January-March (resulting in less evaporative cooling) and the warm SSTs observed for canonical relative to Modoki between 0 N and 30 N and 25 W and 60 W during March-May (see Figure 5b).”

May combine two claims.

For the canonical and Modoki composites, the SST anomalies in the tropical North Atlantic are more widespread and spatially coherent than the wind anomalies, suggesting that other processes besides wind-induced evaporative cooling may contribute significantly to the anomalous changes in SST.

“For the canonical and Modoki composites, the SST anomalies in the tropical North Atlantic are more widespread and spatially coherent than the wind anomalies, suggesting that other processes besides windinduced evaporative cooling may contribute significantly to the anomalous changes in SST.”

May combine two claims.

Results were consistent for events peaking in NDJ and NDJF, though DJF yielded the most statistically robust composites.

“To test our results' sensitivity to the season used to define events (e.g., NDJ as opposed to DJF), the analysis was repeated for events peaking in NDJ and NDJF.Results were consistent for each defining season; however, DJF yielded the most statistically robust composites.”

May combine two claims.

A significantly warmer tropospheric temperature for canonical relative to Modoki in this region will tend to increase static stability and reduce convection, in turn reducing the strength of the northeasterly trade winds.

“A significantly warmer tropospheric temperature for canonical relative to Modoki in this region will tend to increase static stability and reduce convection, in turn reducing the strength of the northeasterly trade winds.”

May combine two claims.

For canonical events, anomalous southwesterly surface winds during winter weaken the northeasterly trade winds, decreasing evaporative cooling and leading to the boreal spring peak in anomalous SST.

“Anomalous southwesterly surface winds during the winter weaken the northeasterly trade winds, decreasing evaporative cooling and leading to the boreal spring peak in anomalous SST.”

Classified as probably not a substantial claim. May combine two claims.

Because there is not a consensus on which index best captures noncanonical El Niño variability, the analysis was repeated for each noncanonical index.

“However, since there is not a consensus on which index best captures noncanonical El Niño variability, we repeat our analysis for each of the noncanonical indices mentioned above.”

Classified as probably not a substantial claim.

The solar radiation results should be viewed with caution because of the lower quality of the solar radiation data in comparison to SST and surface winds.

“However, these results should be viewed with caution because of the lower quality of the solar radiation data in comparison to SST and surface winds.”

May combine two claims.

Results are similar for other thresholds (multiples of the standard deviation of 0.3-0.7) and for other noncanonical indices.

“Results are also similar for other thresholds (multiples of the standard deviation of 0.3-0.7),and for other noncanonical indices, as discussed in the following section and shown in Tables 1 and 2.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The ERSST.v3b data set extending back more than a century has been used successfully in past El Niño studies.

“The ERSST.v3b data set extending back more than a century has been used successfully in past El Niño studies [e.g., Yeh et al., 2009;Messi e and Chavez, 2011].”

• cites Yeh et al., 2009 sourceNot checked — no full text of the source
• cites Messi e and Chavez, 2011Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Classified as probably not a substantial claim.

Previous studies have shown that canonical El Niños tend to suppress Atlantic hurricane activity in the boreal summer and fall.

“Previous studies have shown that canonical El Niños tend to suppress Atlantic hurricane activity in the boreal summer and fall [e.g., Goldenberg and Shapiro, 1996;Klotzbach, 2011a].”

• cites Goldenberg and Shapiro, 1996Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Klotzbach, 2011aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

The result is a band of anomalously weak winds for canonical relative to Modoki, which tends to reduce evaporative cooling and increase SST.

“The result is a band of anomalously weak winds for canonical relative to Modoki, which tends to reduce evaporative cooling and increase SST.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Lee and McPhaden [2010] showed a growing intensity of central Pacific warming events during the past decade.

“Further, Lee and McPhaden, [2010] showed a growing intensity of central Pacific warming events during the past decade, though later studies indicate that this trend likely arises from unresolved natural decadal variability [McPhaden et al., 2011;Yeh et al., 2011].”

• cites Lee and McPhaden, [2010] sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S4 (based).

The positioning of Modoki events closer to the climatological warm pool in the western equatorial Pacific would tend to result in a stronger atmospheric response for a given SST anomaly compared to the response for the same anomaly in the eastern equatorial Pacific associated with a canonical event.

“On the one hand, the positioning of Modoki events closer to the climatological warm pool in the western equatorial Pacific would tend to result in a stronger atmospheric response for a given SST anomaly compared to the response for the same anomaly in the eastern equatorial Pacific associated with a canonical event.”

• AssumptionRests on an assumption: Modoki events are positioned closer to the climatological warm pool in the western equatorial Pacific.

May combine two claims.

The differences in boreal spring and summer stem from the combination of a stronger Pacific/North America teleconnection pattern and a stronger atmospheric Kelvin wave response for canonical events relative to Modoki, which decreases the strength of the tropical North Atlantic trade winds and increases SST.

“The differences in boreal spring and summer stem from the combination of a stronger Pacific/North America teleconnection pattern and a stronger atmospheric Kelvin wave response for canonical events relative to Modoki, which decreases the strength of the tropical North Atlantic trade winds and increases SST.”