“…The spatial pattern had evolved into the CEOF1-like pattern by the end of 2014 (the AL and the subtropical high in the SLP anomalies with PDO/ENSO pattern in the SST anomalies; see figure 1(f)). But the subtropical high in the western Pacific is not very intense with a weak zonal dipole in the tropics, suggesting a very weak El Niño like phenomena (Central Pacific warming signature, see Tseng et al 2017). In the extratropical Pacific, we can still observe a similar meridional dipole of SLP anomalies with an enhanced southern pole (i.e.…”
Section: Resultsmentioning
confidence: 73%
“…The surface patterns associated with these VM events did not extend far enough toward the equator compared with those associated with other VM events related to ENSO. To initiate ENSO development, the preconditioned tropical subsurface heat content and its propagation are required to provide favorable tropical ocean conditions at interannual time scales (Chen et al 2015, Levine and McPhaden 2016, Tseng et al 2017. In terms of the 2015/16 El Niño, the warm water content was high from spring 2014 to early 2016 (www.pmel.…”
Section: Discussionmentioning
confidence: 99%
“…Rather, it is a basin-scale transition process bridging the extratropical forcing and ENSO variation. The reduced net surface heat fluxes shown in winter 2013/14 (Bond et al 2015) are consistent with the NPO forcing on the VM and previous winter studies in the North Pacific.After the VM reaches the mature phase in March 2014 (with a band of significant SST anomalies in the subtropical central to eastern North Pacific) with a decreasing atmospheric impact, the coupled positive wind-evaporation-SST feedback becomes active, contributing to subsequent equatorward development of warm SST anomalies in the central-eastern Pacific as the ENSO develops(Ding et al (2015a), see also figure 10 inTseng et al (2017) and its associated discussion on the tropical evolution in 2014). This warming enhances the SST zonal gradient across the tropical Pacific, thus forcing the anomalous southwesterlies in the western tropical Pacific (figure 1) from spring to summer 2014.…”
We address the occurrence of the warm anomaly, known as the Blob, that developed from late 2013 to 2015 in the northeast Pacific and its connection with the El Niño-Southern Oscillation (ENSO) variability. The warm Blob results from the enhanced second ocean-atmosphere (O-A) coupled mode of variability in the tropical and North Pacific, representing a small part of the Victoria mode (VM) in the northeast Pacific forced by the strengthened North Pacific Oscillation-like atmospheric pattern since 2013. We also show that this second O-A mode reflects the meridional variability through the tropical-extratropical teleconnection and is an important precursor to the ENSO variability. The process is confirmed by the coupled patterns that evolved from late 2013 to 2016 and the multi-year persistence of the warm Blob. We emphasize the role of evolving basin-scale VM but not the warm Blob itself prior to the ENSO variability. Hence, the Blob and the most recent 2015/16 El Niño, which differs significantly from the other large El Niños in terms of the triggering hemisphere, are actually linked rather than independent phenomena.
“…The spatial pattern had evolved into the CEOF1-like pattern by the end of 2014 (the AL and the subtropical high in the SLP anomalies with PDO/ENSO pattern in the SST anomalies; see figure 1(f)). But the subtropical high in the western Pacific is not very intense with a weak zonal dipole in the tropics, suggesting a very weak El Niño like phenomena (Central Pacific warming signature, see Tseng et al 2017). In the extratropical Pacific, we can still observe a similar meridional dipole of SLP anomalies with an enhanced southern pole (i.e.…”
Section: Resultsmentioning
confidence: 73%
“…The surface patterns associated with these VM events did not extend far enough toward the equator compared with those associated with other VM events related to ENSO. To initiate ENSO development, the preconditioned tropical subsurface heat content and its propagation are required to provide favorable tropical ocean conditions at interannual time scales (Chen et al 2015, Levine and McPhaden 2016, Tseng et al 2017. In terms of the 2015/16 El Niño, the warm water content was high from spring 2014 to early 2016 (www.pmel.…”
Section: Discussionmentioning
confidence: 99%
“…Rather, it is a basin-scale transition process bridging the extratropical forcing and ENSO variation. The reduced net surface heat fluxes shown in winter 2013/14 (Bond et al 2015) are consistent with the NPO forcing on the VM and previous winter studies in the North Pacific.After the VM reaches the mature phase in March 2014 (with a band of significant SST anomalies in the subtropical central to eastern North Pacific) with a decreasing atmospheric impact, the coupled positive wind-evaporation-SST feedback becomes active, contributing to subsequent equatorward development of warm SST anomalies in the central-eastern Pacific as the ENSO develops(Ding et al (2015a), see also figure 10 inTseng et al (2017) and its associated discussion on the tropical evolution in 2014). This warming enhances the SST zonal gradient across the tropical Pacific, thus forcing the anomalous southwesterlies in the western tropical Pacific (figure 1) from spring to summer 2014.…”
We address the occurrence of the warm anomaly, known as the Blob, that developed from late 2013 to 2015 in the northeast Pacific and its connection with the El Niño-Southern Oscillation (ENSO) variability. The warm Blob results from the enhanced second ocean-atmosphere (O-A) coupled mode of variability in the tropical and North Pacific, representing a small part of the Victoria mode (VM) in the northeast Pacific forced by the strengthened North Pacific Oscillation-like atmospheric pattern since 2013. We also show that this second O-A mode reflects the meridional variability through the tropical-extratropical teleconnection and is an important precursor to the ENSO variability. The process is confirmed by the coupled patterns that evolved from late 2013 to 2016 and the multi-year persistence of the warm Blob. We emphasize the role of evolving basin-scale VM but not the warm Blob itself prior to the ENSO variability. Hence, the Blob and the most recent 2015/16 El Niño, which differs significantly from the other large El Niños in terms of the triggering hemisphere, are actually linked rather than independent phenomena.
“…16). Also, the evolution of subsurface ocean temperature in these large positive Bjerknes feedback regions (175°E–155°W) has been proposed as a predictor for ENSO initiation and to monitor oceanic Kelvin wave propagation 21 .Figure 4Simultaneous regressions of zonal wind stress anomalies onto the Niño3 index, which was referred to as the Bjerknes feedback. Contours (shadings) are for the regressions in Jan 1979–Dec 1999 (Jan 2000–Dec 2016).…”
The possible factors associated with the shortening of lead time between ocean warm water volume (WWV) variability along the equatorial Pacific and El Niño–Southern Oscillation (ENSO) variability after 2000 are documented. It is shown that the shortening of lead time is due to frequency increases of both WWV and ENSO. During 1979–99 the dominant frequencies were 1.5–3.5 years for both the Niño3.4 and WWV indices. In contrast, during 2000–16, both indices had a relatively flatter spectrum and were closer to a white noise process with a relative maximum at 1.5–2.0 years for the Niño3.4 index and 0.8–1.3 years for the WWV index. The frequency change of ENSO and WWV were linked to a westward shift of the Bjerknes feedback region. The results here are consistent with previous argument that the westward shift of the air-sea coupling region will cause an increase of ENSO frequency, as the corresponding zonal advection feedback reduces the period and growth of coupled instability, thus favoring more frequent and weak El Niño events.
“…Skillful prediction of ENSO is possible up to a lead time of approximately one year (Latif et al 1994;Barnston 2015). Although interannual climate prediction has improved in the past decades (Solow et al 1998;Tippett and Barnston 2008;Tseng et al 2017;Hu et al 2019), the ENSO forecast remains challenging because of model and observation errors, as well as the intrinsically volatile nature of the ocean-atmosphere system (Tippett and Barnston 2008). Recognizing that ENSO forecast is highly probabilistic, the uncertainty of such forecast should be incorporated into the evaluation process.…”
Agricultural production is substantially affected by the variations in global weather patterns, particularly by the El Niño–Southern Oscillation (ENSO). Thus, incorporating the forecast of imminent ENSO phases can enhance the effectiveness of crop insurance and mitigate the adverse impacts of weather on agriculture. Given the probabilistic nature of the ENSO phase forecast, we employ a Bayesian framework to estimate the value of ENSO information on various aspects of crop insurance. Our results indicate potential benefits of ENSO forecast to insurance rate setting and policy selection. At the same time, we caution against overoptimism in this assessment as economic benefits may diminish as the accuracy of ENSO forecast decreases. Simulations and numerical experiments demonstrate the practical usefulness of the proposed method for various stakeholders of the US crop insurance industry. Implications to various crop insurance policies are also discussed.
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