A variable sea surface temperature threshold for tropical convection.

Evans, Jenni L.; Webster, Casey

doi:10.22499/2.6401.007

Cited by 20 publications

(28 citation statements)

References 20 publications

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“…Within a simplified dynamical framework, the mean value of reconstructed Caribbean SST after the early Holocene transition remains around the estimated critical SST threshold of~27.5°C needed to trigger atmospheric deep convection in the tropics 52 . However, the covariation between tropical-mean SSTs and the convective threshold revealed by satellite data 53 suggests that such a threshold depends, to some extent, on the background climate conditions, and it might have been lower than for present-day climates in the early post-glacial era.…”

Section: Resultsmentioning

confidence: 95%

Initiation of a stable convective hydroclimatic regime in Central America circa 9000 years BP

et al. 2020

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Many Holocene hydroclimate records show rainfall changes that vary with local orbital insolation. However, some tropical regions display rainfall evolution that differs from gradual precessional pacing, suggesting that direct rainfall forcing effects were predominantly driven by sea-surface temperature thresholds or inter-ocean temperature gradients. Here we present a 12,000 yr continuous U/Th-dated precipitation record from a Guatemalan speleothem showing that Central American rainfall increased within a 2000 yr period from a persistently dry state to an active convective regime at 9000 yr BP and has remained strong thereafter. Our data suggest that the Holocene evolution of Central American rainfall was driven by exceeding a temperature threshold in the nearby tropical oceans. The sensitivity of this region to slow changes in radiative forcing is thus strongly mediated by internal dynamics acting on much faster time scales.

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Section: Resultsmentioning

confidence: 95%

Initiation of a stable convective hydroclimatic regime in Central America circa 9000 years BP

et al. 2020

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“…Studies of the tropical Pacific often focus on the equatorial waveguide and the propagation of equatorial Kelvin waves generated by westerly wind events (i.e. Levine and McPhaden, 2016;Chen et al, 2016;Hu and Fedorov, 2017). The study reported here starts in a similar manner, focusing on the waveguide.…”

Section: Introductionmentioning

confidence: 99%

“…In order to clarify the situation, model archived data are used to calculate the flux of warm water across 180 and 240 • E as a function of time during the period 1980 to 1985. This period includes the strong 1982-1983 The study by Evans and Webster (2014) showed that sea surface temperatures (SSTs) greater than 28 • C are required for the onset of widespread deep convection over the tropical ocean. They also showed that at times temperatures of over 29.5 • C may be required.…”

Section: Introductionmentioning

confidence: 99%

On the role of the North Equatorial Counter Current during a strong El Niño

Webb

2018

Ocean Sci.

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Abstract. An analysis of archived data from the NEMO 1∕12th degree global ocean model shows the importance of the North Equatorial Counter Current (NECC) in the development of the strong 1982–1983 and 1997–1998 El Niños. The model results indicate that in a normal year the core of warm water in the NECC is diluted by the surface Ekman transport, by geostrophic inflow and by tropical instability waves. During the development of the 1982–1983 and 1997–1998 El Niños, these processes had reduced effect at the longitudes of warmest equatorial temperatures and to the west. During the autumns of 1982 and 1997, the speed of the NECC was also increased by a stronger-than-normal annual Rossby wave. The increased transport of warm water by the NECC due to these changes resulted in warm water reaching the far eastern Pacific and appears to have been a major factor in moving the centre of deep atmospheric convection eastwards across the Pacific.

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“…The rqq plots tend to converge toward a residual of about 1 °C above SST values around 29 °C. A plausible physical mechanism explaining this convergence is connected with the emergence of deep atmospheric convection only for SST exceeding a critical threshold value in the range 27-28 °C 28,29 and its increasing efficiency with increasing SSTs. The rqq plots further reveal that, in many buoys, SSTs have larger variance than nMAT, as shown by residuals predominantly increasing with SST.…”

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confidence: 99%

On the interchangeability of sea-surface and near-surface air temperature anomalies in climatologies

Rubino

Zanchettin

Rovere

et al. 2020

Sci Rep

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on global and hemispheric scales, sea-surface temperature (SSt) anomalies are assumed to be good surrogates for near-surface marine air temperature (MAt) anomalies. in fact, global gridded temperature datasets commonly blend SSt and near-surface air temperature anomalies to overcome the lack of geographically homogeneous and reliable MAt observations. Here, we show that SSt and MAT anomalies differ regarding crucial statistical properties such as multiannual trends and probabilistic distributions of daily and monthly averages. We provide evidence of the lack of interchangeability from an array of moored buoys in the tropical Pacific Ocean. We identify statistically significant discrepancies between SSt and MAt anomalies for single as well as groups of such buoys. thus, caution is required when characterizing and interpreting MAt variability through SSt observations, especially at shorter than decadal timescale. Near-surface air temperature observations over the oceans-the large majority of the Earth's surface area-are relatively scarce. Until a few decades ago, they were limited to coastal areas and major shipping routes 1. Nowadays, several monitoring programs are active in different oceanic regions. Among them, the Tropical Atmosphere Ocean (TAO) project was initiate in the 1980s to meet the growing needs of monitoring, understanding and predicting El Niño events and related phenomena 2. The TAO array (now referred to as TAO/TRITON) consists of about 70 moorings covering the Tropical Pacific Ocean that currently provide multidecadal time series of surface and near-surface oceanographic and meteorological variables, including sea-surface temperature (SST) and near-surface marine air temperature (MAT). Several attempts have been undertaken by the climate research community to merge information from the poorly observed early decades to the better observed recent decades and generate spatially homogeneous global gridded temperature datasets covering the full instrumental period 3-8. In such datasets, near-surface air temperature anomalies over land and SST anomalies are commonly blended, assuming that at the hemispheric and larger scales SST variations are good surrogates of MAT variations 9,10. In this sense, many studies have reported on the similarity between MAT and SST anomalies on large (global and hemispheric) spatial scales 9-20. A comparative analysis of SST and satellite-measured MAT shows that, notwithstanding a distinct difference between both variables, about 80% of the variance of one is captured by the other 21. Then, night-time MAT (nMAT) estimates are used to identify and remove SST biases to construct climate data records of SSTs in SST datasets 22. Accordingly, during the past few decades, global gridded surface temperature datasets over the ocean have been extensively used to put oceanic climate variability in the context of global climate change 23. Still, some studies point to issues potentially affecting the comparability between SST and MAT at large (even global) scales. Among them, MAT-SST ...

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A variable sea surface temperature threshold for tropical convection.

Cited by 20 publications

References 20 publications

Initiation of a stable convective hydroclimatic regime in Central America circa 9000 years BP

Initiation of a stable convective hydroclimatic regime in Central America circa 9000 years BP

On the role of the North Equatorial Counter Current during a strong El Niño

On the interchangeability of sea-surface and near-surface air temperature anomalies in climatologies

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