Enhanced Predictability of Eastern North Pacific Tropical Cyclone Activity Using the ENSO Longitude Index

Balaguru, Karthik; Patricola, Christina M.; Hagos, Samson; Leung, L. Ruby; Dong, Lu

doi:10.1029/2020gl088849

Cited by 6 publications

(3 citation statements)

References 60 publications

(93 reference statements)

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“…The monthly ELI is thus defined as this average longitude at which SSTs are greater than the threshold temperature for deep convection. We note that the calculation of ELI considers whether the convective threshold is exceeded, and ELI is not weighted by how much the convective threshold is exceeded; nevertheless, ELI explains the global responses of precipitation, temperature, and tropical cyclones at least as well as the Niño3.4 index (Balaguru et al, 2020;Magee & Kiem, 2020;Patricola et al, 2020Patricola et al, , 2022Williams & Patricola, 2018). There is a high correlation between the Niño3.4 index and ELI (R = 0.86 for the December-February (DJF) averages over 1870-2021), which is due to a strong relationship between the two indices for La Niña, neutral ENSO, and weak El Niño events (Figure 1a of Williams & Patricola, 2018); however, the correlation breaks down for strong El Niño events, which ELI is particularly well-suited to capture.…”

Section: Methodsmentioning

confidence: 99%

Future Projections of the El Niño—Southern Oscillation and Tropical Pacific Mean State in CMIP6

Erickson,

Patricola

2023

JGR Atmospheres

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The El Niño—Southern Oscillation (ENSO) is an important mode of tropical Pacific atmosphere‐ocean variability that drives teleconnections with weather and climate globally. However, prior studies using state‐of‐the‐art climate models lack consensus regarding future ENSO projections and are often impacted by tropical Pacific sea‐surface temperature (SST) biases. We used 173 simulations from 29 climate models participating in the Coupled Model Intercomparison Project, version 6 (CMIP6) to analyze model biases and future ENSO projections. We analyzed two ENSO indices, namely the ENSO Longitude Index (ELI), which measures zonal shifts in tropical Pacific deep convection and accounts for changes in background SST, and the Niño 3.4 index, which measures SST anomalies in the central‐eastern equatorial Pacific. We found that the warm eastern tropical‐subtropical Pacific SST bias typical of previous generations of climate models persists into many of the CMIP6 models. Future projections of ENSO shift toward more El Niño‐like conditions based on ELI in 48% of simulations and 55% of models, in association with a future weakening of the zonal equatorial Pacific SST gradient. On the other hand, none of the models project a significant shift toward La Niña‐like conditions. The standard deviation of the Niño 3.4 index indicates a lack of consensus on whether an increase or decrease in ENSO variability is expected in the future. Finally, we found a possible relationship between historical SST and low‐level cloud cover biases in the ENSO region and future changes in ELI; however, this result may be impacted by limitations in data availability.

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Section: Methodsmentioning

confidence: 99%

Future Projections of the El Niño—Southern Oscillation and Tropical Pacific Mean State in CMIP6

Erickson,

Patricola

2023

JGR Atmospheres

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“…ELI has several advantages: it accounts for the nonlinear response of deep convection to SST, it accounts for changes in background SST state associated with the seasonal cycle and/or climate change, and it uniquely captures the diversity of ENSO's spatial patterns of warming, eliminating the need to categorize different types or “flavors” of El Niño events. The utility of ELI has been demonstrated broadly, as it has been applied to operational seasonal TC prediction in the North Atlantic (Klotzbach et al., 2021) and the South West Pacific (Magee et al., 2020), and can improve seasonal prediction of eastern North Pacific TC activity (Balaguru et al., 2020) and western US winter precipitation (Patricola et al., 2020). In addition to the ELI, we also use the Niño 3.4 index, which represents SSTAs averaged over 170–120°W, 5°S–5°N, in the eastern‐central equatorial Pacific.…”

Section: Methodsmentioning

confidence: 99%

Tropical Oceanic Influences on Observed Global Tropical Cyclone Frequency

Patricola

Cassidy

Klotzbach

2022

Geophysical Research Letters

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The global tropical cyclone (TC) number has historically been relatively constant from year‐to‐year, however, the reason remains unknown. Furthermore, climate projections are inconclusive regarding future global TC frequency changes. Here, we investigated years in which observed global TC activity deviated from the mean and potential links to ocean drivers from 1980 to 2021. We found that the annual global number of named storm days and accumulated cyclone energy (ACE) were significantly linked with El Niño–Southern Oscillation (ENSO) and the Atlantic Meridional Mode (AMM). La Niña and positive AMM are associated with the bottom percentiles of both TC metrics, and vice versa for El Niño and negative AMM. The ENSO Longitude Index explains variability in annual global named storm days and ACE as well as the Niño 3.4 index. This research reveals that reliable future projections of ENSO are necessary, but not sufficient, to understand future changes in global TC frequency.

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“…In the tropics, ENSO events are accompanied by robust upper‐ocean heat content change on the interannual time‐scale (e.g., Jin, 1997), which makes ENSO an important factor in affecting TC intensity as well as RI (e.g., Guo & Tan, 2018b). There is mounting evidence for a relationship between ENSO and TC activity, including RI (e.g., Balaguru et al., 2020; Camargo & Sobel, 2005; Chan, 2000; Guo & Tan, 2018b; Wang & Chan, 2002; Zhan et al., 2011; Zhao et al., 2010). It is generally accepted that TCs tend to form in the southeastern quadrant of the WNP during El Niño years.…”

Section: Introductionmentioning

confidence: 99%

Influence of Different ENSO Types on Tropical Cyclone Rapid Intensification Over the Western North Pacific

Guo

Tan

2021

JGR Atmospheres

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This study investigates the influence of different types of El Niño‐Southern Oscillation (ENSO) on the properties of tropical cyclone (TC) rapid intensification (RI) over the western North Pacific (WNP). The RI numbers during all types of ENSO events have no significant difference from that of neutral years, except that eastern Pacific (EP) El Niño corresponds to fewer RI cases. The most robust response of RI properties is occurrence position. The mean RI occurrence position in La Niña events shifts northwards by about 2° in latitude during the peak TC season (July–September), which may be related to the northwestward shift of TC genesis positions. On the other hand, the mean RI occurrence positions during EP El Niño and La Niña events in the late TC season (October–December) shift westwards by about 10° and 14° in longitude, respectively. This westward shift in RI occurrence positions is mainly caused by the favorable conditions over the western part of the WNP in the late TC season. During October–December, EP El Niño shifts to a La Niña phase and warms the upper ocean of the western part of the WNP. La Niña events result in similar upper ocean conditions because they maintain negative phases during October–December. The warmed upper ocean is also accompanied by a moistened mid‐troposphere and weakened vertical wind shear, which are favorable for RI occurrence.

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Enhanced Predictability of Eastern North Pacific Tropical Cyclone Activity Using the ENSO Longitude Index

Cited by 6 publications

References 60 publications

Future Projections of the El Niño—Southern Oscillation and Tropical Pacific Mean State in CMIP6

Future Projections of the El Niño—Southern Oscillation and Tropical Pacific Mean State in CMIP6

Tropical Oceanic Influences on Observed Global Tropical Cyclone Frequency

Influence of Different ENSO Types on Tropical Cyclone Rapid Intensification Over the Western North Pacific

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