Tropical rainfall, Rossby waves and regional winter climate predictions

Scaife, Adam A.; Comer, Ruth; Dunstone, Nick; Knight, Jeff; Smith, Doug; MacLachlan, Craig; Martin, Nicola; Peterson, K. Andrew; Rowlands, Dan; Carroll, E B; Belcher, Stephen E.; Slingo, Julia

doi:10.1002/qj.2910

Cited by 167 publications

(199 citation statements)

References 72 publications

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“…ENSO teleconnections provide a potential predictability source of extratropical climate prediction skill on seasonal (e.g., Jia et al 2012;Jeong et al 2012;Lee and Ha 2015;Scaife et al 2017a) and perhaps longer interannual timescales. However, it is difficult from observational records to decide whether these influences are variable from one event to another (e.g., Greatbatch et al 2004;Toniazzo and Scaife 2006), or simply the same in all events but masked in some cases by other climate variability so that long records are required to extract stable teleconnections ).…”

Section: Patterns Of Teleconnectionsmentioning

confidence: 99%

Seasonal predictability of winter ENSO types in operational dynamical model predictions

et al. 2018

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The El Niño-Southern Oscillation (ENSO) events of recent decades have been divided into the two different types based on their spatial patterns, the Eastern Pacific (EP) type and Central Pacific (CP) type. Their most significant difference is the distinguished zonal center locations of sea surface temperature (SST) anomalies in the equatorial Pacific. In this study, based on six operational climate models, we evaluate predictability of the two types of ENSO events in winter to examine whether dynamical predictions can distinguish between the two spatial patterns at lead time of 1 month and tell us more than simply whether an event is on the way. We show that winter EP and CP El Niño and La Niña events can only be distinguished in a minority of these models at 1-month lead, and the EP type tends to has a more realistic zonal positions of SST pattern centers than the CP type. Compared to the SST patterns, the differences between the two types are less apparent in precipitation especially for the two La Niña types in the models. Examinations of the extratropical teleconnections to the two ENSO types show that some of the models can reproduce the differences between EP and CP teleconnections. Evaluations of model predictions show that the EP El Niño event has the same level hit rate with the CP El Niño and the CP La Niña event has much higher hit rate than the EP La Niña. While the multi-model ensemble increases Niño index prediction skill, it does not help to improve forecast skill of center longitude index of the SST patterns and distinguish the two types of ENSO events. Although ENSO skill is very high at this lead time, the rapid loss of the initialized information on the different ENSO types in most of the models severely limits the predictability of the two types of winter ENSO events and more research is needed to improve the performance of climate models in forecasting the two ENSO types.

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Section: Patterns Of Teleconnectionsmentioning

confidence: 99%

Seasonal predictability of winter ENSO types in operational dynamical model predictions

et al. 2018

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“…Following Scaife et al (2017), the monthly data was used to calculate the Rossby wave source for observations and model simulations at the 200-hPa-pressure level. The absolute vorticity, divergence, and divergent winds were calculated using the standard scripts from the NCAR Command Language (Version 6.4.0, https ://doi.org/10.5065/D6WD3 XH5).…”

Section: Rossby Wave Source Calculationmentioning

confidence: 99%

On the seasonal prediction of the western United States El Niño precipitation pattern during the 2015/16 winter

et al. 2018

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A "typical" El Niño leads to wet (dry) wintertime anomalies over the southern (northern) half of the Western United States (WUS). However, during the strong El Niño of 2015/16, the WUS winter precipitation pattern was roughly opposite to this canonical (average of the record) anomaly pattern. To understand why this happened, and whether it was predictable, we use a suite of high-resolution seasonal prediction experiments with coupled climate models. We find that the unusual 2015/16 precipitation pattern was predictable at zero-lead time horizon when the ocean/atmosphere/land components were initialized with observations. However, when the ocean alone is initialized the coupled model fails to predict the 2015/16 pattern, although ocean initial conditions alone can reproduce the observed WUS precipitation during the 1997/98 strong El Niño. Further observational analysis shows that the amplitudes of the El Niño induced tropical circulation anomalies during 2015/16 were weakened by about 50% relative to those of 1997/98. This was caused by relative cold (warm) anomalies in the eastern (western) tropical Pacific suppressing (enhancing) deep convection anomalies in the eastern (western) tropical Pacific during 2015/16. The reduced El Niño teleconnection led to a weakening of the subtropical westerly jet over the southeast North Pacific and southern WUS, resulting in the unusual 2015/16 winter precipitation pattern over the WUS. This study highlights the importance of initial conditions not only in the ocean, but in the land and atmosphere as well, for predicting the unusual El Niño teleconnection and its influence on the winter WUS precipitation anomalies during 2015/16.

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“…In particular, a good representation of the MJO on intraseasonal to interannual time scales is important; indeed we have seen here the influence of MJO and [U150] E . In this context, Scaife et al (2016) have noted the importance of the tropics in the success of Met Office seasonal predictions. When interseasonal to decadal forecasts are considered, a proper initialization of the model is necessary to capture the phasing of ENSO to make use of its impacts onto the extratropics (e.g., Ding et al 2013).…”

Section: Gollanmentioning

confidence: 99%

The Relationship between Northern Hemisphere Winter Blocking and Tropical Modes of Variability

Gollan

Greatbatch

2017

J. Climate

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In the present study, the influence of some major tropical modes of variability on Northern Hemisphere regional blocking frequency variability during boreal winter is investigated. Reanalysis data and an ensemble experiment with the ECMWF model using relaxation toward the ERA-Interim data inside the tropics are used. The tropical modes under investigation are El Niño-Southern Oscillation (ENSO), the Madden-Julian oscillation (MJO), and the upper-tropospheric equatorial zonal-mean zonal wind [U150] E . An early (late) MJO phase refers to the part of the MJO cycle when enhanced (suppressed) precipitation occurs over the western Indian Ocean and suppressed (enhanced) precipitation occurs over the Maritime Continent and the western tropical Pacific. Over the North Pacific sector, it is found that enhanced (suppressed) high-latitude blocking occurs in association with El Niño (La Niña) events, late (early) MJO phases, and westerly (easterly) [U150] E . Over central to southern Europe and the east Atlantic, it is found that late MJO phases, as well as a suppressed MJO, are leading to enhanced blocking frequency. Furthermore, early (late) MJO phases are followed by blocking anomalies over the western North Atlantic region, similar to those associated with a positive (negative) North Atlantic Oscillation. Over northern Europe, the easterly (westerly) phase of [U150] E is associated with enhanced (suppressed) blocking. These results are largely confirmed by both the reanalysis and the model experiment.

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Tropical rainfall, Rossby waves and regional winter climate predictions

Cited by 167 publications

References 72 publications

Seasonal predictability of winter ENSO types in operational dynamical model predictions

Seasonal predictability of winter ENSO types in operational dynamical model predictions

On the seasonal prediction of the western United States El Niño precipitation pattern during the 2015/16 winter

The Relationship between Northern Hemisphere Winter Blocking and Tropical Modes of Variability

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