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Jae-heung Park - One of the best experts on this subject based on the ideXlab platform.
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Role of the western hemisphere Warm Pool in climate variability over the western North Pacific
Climate Dynamics, 2019Co-Authors: Jae-heung Park, Jong-seong Kug, Soon-il An, Tim LiAbstract:The climate variability in the Western North Pacific (WNP), which is surrounded by densely populated countries, is closely tied to the lives of the people in the East Asia in terms of climate and socioeconomics. Along with global Warming, remarkable interannual and interdecadal variations in sea surface temperature (SST) and sea surface height have been observed in the WNP. Here we demonstrated that boreal summer SST variability in the western hemisphere Warm Pool (WHWP, a.k.a. Atlantic Warm Pool) near the Intra-Americas Sea, which is known as the second largest Warm Pool on the planet, has considerably contributed to the climate variability in the WNP in subsequent winter. This is possible due to westward propagation of Rossby waves associated with a WHWP-SST Warming (cooling) in mid-summer to early fall season, which induces northerly (southerly) wind anomalies over the North Pacific. In the presence of northeasterly mean trade winds, the anomalous meridional winds interact with SST and precipitation anomalies. Such air-sea coupling processes gradually move equatorward and westward along the climatological migration of the Pacific Intertropical Convergence Zone, and it has finally an effect on the climate variability over the WNP in winter. Further diagnosis verifies that WHWP-WNP connection exists not only on interannual time scale but also on decadal time scale. The analysis using state-of-the-art climate models reasonably supports this argument. A better understanding of the WHWP influence is expected to improve forecasts for the WNP climate and assist socioeconomic development in the East Asia.
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Predicting El Niño Beyond 1-year Lead: Effect of the Western Hemisphere Warm Pool.
Scientific reports, 2018Co-Authors: Jae-heung Park, Jong-seong Kug, Swadhin K. BeheraAbstract:Due to the profound impact of El Nino-Southern Oscillation (ENSO) on global climate and weather, extensive research has been devoted to its prediction. However, prediction accuracy based on observation is still insufficient and largely limited to less than one year of lead time. In this study, we demonstrate the possibility that anomalous sea surface temperature (SST) Warming (cooling) in the Western Hemisphere Warm Pool (WHWP, a.k.a. Atlantic Warm Pool) near the Intra-Americas Sea (IAS), which is the second largest Warm Pool on the planet, contributes to the initiation of La Nina (El Nino) with a 17-month lag time. SST anomalies in WHWP in late boreal summer contribute significantly to the emergence of the Pacific meridional mode (PMM) via interaction between the ocean and atmosphere over the subtropical North Pacific during the subsequent winter and spring. Near-equatorial surface wind anomalies associated with the PMM can further trigger ENSO through the dynamics of the equatorial oceanic waves. Thus, this observational analysis presents a clear step-by-step explanation about the influence of WHWP on ENSO development with a 17-month lead time.
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recent and future sea surface temperature trends in tropical pacific Warm Pool and cold tongue regions
Climate Dynamics, 2012Co-Authors: Jiwon Kim, Beak Min Kim, Jae-heung ParkAbstract:Using coral data, sea surface temperature (SST) reanalysis data, and Climate Model Intercomparison Project III (CMIP3) data, we analyze 20th-century and future Warm Pool and cold tongue SST trends. For the last 100 years, a broad La Nina-like SST trend, in which the Warming trend of the Warm Pool SST is greater than that of the cold tongue SST, has appeared in reanalysis SST data sets, 20C scenario experiments of the CMIP3 data and less significantly in coral records. However, most Coupled General Circulation Models subjected to scenarios of future high greenhouse gas concentrations produce larger SST Warming trends in cold tongues than in Warm Pools, resembling El Nino-like SST patterns. In other words, Warmer tropical climate conditions correspond to stronger El Nino-like response. Heat budget analyses further verify that Warmer tropical climates diminish the role of the ocean’s dynamic thermostat, which currently regulates cold tongue temperatures. Therefore, the thermodynamic thermostat, whose efficiency depends on the mean temperature, becomes the main regulator (particularly via evaporative cooling) of both Warm Pool and cold tongue temperatures in future Warm climate conditions. Thus, the Warming tendency of the cold tongue SST may lead that of the Warm Pool SST in near future.
David B Enfield - One of the best experts on this subject based on the ideXlab platform.
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What drives the seasonal onset and decay of the Western Hemisphere Warm Pool
Journal of Climate, 2007Co-Authors: Sang-ki Lee, David B Enfield, Chunzai WangAbstract:The annual heat budget of the Western Hemisphere Warm Pool (WHWP) is explored using the output of an ocean general circulation model (OGCM) simulation. According to the analysis, the WHWP cannot be considered as a monolithic whole with a single set of dominating processes that explain its behavior. The three regions considered, namely the eastern north Pacific (ENP), the Gulf of Mexico (GoM), and the Caribbean Sea (CBN), are each unique in terms of the atmospheric and oceanic processes that dominate the corresponding heat budgets. In the ENP region, clear-sky shortwave radiation flux is responsible for the growth of the Warm Pool in boreal spring, while increased cloud cover in boreal summer and associated reduction in solar radiation play a crucial role for the ENP Warm Pool’s demise. Ocean upwelling in the Costa Rica Dome connected to surrounding areas by horizontal advection offers a persistent yearlong cooling mechanism. Over the Atlantic, the clear-sky radiation flux that increases monotonically from December to May and decreases later is largely responsible for the onset and decay of the Atlantic-side Warm Pool in boreal summer and fall. The CBN region is affected by upwelling and horizontal advective cooling within and away from the coastal upwelling zone off northern South America during the onset and peak phases, thus slowing down the Warm Pool’s development, but no evidence was found that advective heat flux divergence is important in the GoM region. Turbulent mixing is also an important cooling mechanism in the annual cycle of the WHWP, and the vertical shear at the Warm Pool base helps to sustain the turbulent mixing. Common to all three WHWP regions is the reduction of wind speed at the peak phase, suggestive of a convection–evaporation feedback known to be important in the Indo-Pacific Warm Pool dynamics.
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The Heat Balance of the Western Hemisphere Warm Pool
Journal of Climate, 2005Co-Authors: David B Enfield, Sang-ki LeeAbstract:The thermodynamic development of the Western Hemisphere Warm Pool and its four geographic subregions are analyzed. The subregional Warm Pools of the eastern North Pacific and equatorial Atlantic are best developed in the boreal spring, while in the Gulf of Mexico and Caribbean, the highest temperatures prevail during the early and late summer, respectively. For the defining isotherms chosen ( >= 27.5 degrees, >= 28.0 degrees, >= 28.5 degrees C) the Warm Pool depths are similar to the mixed-layer depth (20-40 m) but are considerably less than the Indo-Pacific Warm Pool depth (50-60 m). The beat balance of the WHWP subregions is examined through two successive types of analysis: first by considering a changing volume ("bubble") bounded by constant temperature wherein advective fluxes disappear and diffusive fluxes can be estimated as a residual, and second by considering a slab layer of constant dimensions with the bubble diffusion estimates as an additional input and the advective heat flux divergence as a residual output. From this sequential procedure it is possible to disqualify as being physically inconsistent four of seven surface heat flux climatologies: the NCEP-NCAR reanalysis (NCEP1) and the ECMWF 15-yr global reanalysis (ERA-15) because they yield a nonphysical diffusion of heat into the Warm Pools from their cooler surroundings, and the unconstrained da Silva and Southampton datasets because their estimated diffusion rates are inconsistent with the smaller rates of the better understood Indo-Pacific Warm Pool when the bubble analysis is applied to both regions. The remaining surface flux datasets of da Silva and Southampton (constrained) and Oberhuber have a much narrower range of slab surface Warming (+25 +/- 5 W m(-2)) associated with bubble residual estimates of total diffusion of -5 to -20 W m(-2) (-5 W m(-2)) and total advective heat flux divergence of -2 to -14 W m(-2) (+/- 5 W m(-2)). The latter are independently confirmed by direct estimates using wind stress data and drifters for the Gulf of Mexico and eastern North Pacific subregions.
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The tropical western hemisphere Warm Pool
Geophysical Research Letters, 2001Co-Authors: David B EnfieldAbstract:The Western Hemisphere Warm Pool (WHWP) of water Warmer than 28.5°C extends from the eastern North Pacific to the Gulf of Mexico and the Caribbean, and at its peak, overlaps with the tropical North Atlantic. It has a large seasonal cycle and its interannual fluctuations of area and intensity are significant. Surface heat fluxes Warm the WHWP through the boreal spring to an annual maximum of SST and areal extent in the late summer/early fall, associated with eastern North Pacific and Atlantic hurricane activities and rainfall from northern South America to the southern tier of the United States. SST and area anomalies occur at high temperatures where small changes can have a large impact on tropical convection. Observations suggest that a positive ocean-atmosphere feedback operating through longwave radiation and associated cloudiness is responsible for the WHWP SST anomalies. Associated with an increase in SST anomalies is a decrease in atmospheric sea level pressure anomalies and an anomalous increase in atmospheric convection and cloudiness. The increase in convective activity and cloudiness results in less longwave radiation loss from the surface, which then reinforces SST anomalies.
Christophe Maes - One of the best experts on this subject based on the ideXlab platform.
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Simulations of the edge of the Western Pacific Warm Pool in CMIP5, and the implications for climate change and ENSO dynamics
2014Co-Authors: Jaclyn N Brown, Christophe Maes, Clothilde Langlais, A. Sen Gupta, F GrahamAbstract:A report from the 1st meeting of the Western Pacific Warm Pool Task Force is given, followed by an exploration of the equatorial edge of the western Pacific Warm Pool. The edge of the Warm Pool separates Warm fresh water from cooler saltier water. Its simulation and how it might change, has implications for marine habitats, rainfall and ENSO dynamics. The simulation of the edge is examined in 19 CMIP5 models, over the historical period and the RCP8.5 scenario. The edge is defined by the isotherm associated with the maximum sea surface salinity gradient. The simulation of the edge has implications for how a model can reproduce ENSO dynamics and is an important component of various paradigms: Delayed Action Oscillator, Advective-Reflective oscillator, and zonal-advective feedback. Projected Warming is revisited by examining changes relative to the edge. The spread in simulated Warming associated with point-wise projections at specific physical locations is reduced when considering changes with respect to the edge of each model’s Warm Pool. Moreover, the pattern of Warming is sensitive to how well the Warm Pool is simulated.
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Detection of the eastern edge of the western Pacific Warm Pool
2011Co-Authors: Christophe Maes, Joël SudreAbstract:The eastward advection of Warm and less saline water from the western Pacific together with the westward advection of cold and more saline water from the central-eastern Pacific induces a convergence of water masses at the eastern edge of the so called western Pacific Warm Pool. The simultaneous zonal migrations of the western Pacific Warm Pool and atmospheric deep convection are essential precursors of the Warming associated with the arrival of El Nino conditions in the eastern Pacific. These zonal displacements, ranging over about one fifth of the equatorial circumference of the Earth, are in phase with the Southern Oscillation and the characteristics of the main parameters involved in the air-sea interactions have been shown to be nearly constant on each side of such convergence zone. The zonal displacements associated with the western Pacific Warm Pool are at the origin of a notable modification of the delayed action oscillator theory, the leading theory for the El Nino‐Southern Oscillation (ENSO) phenomenon. The variability of the eastern edge of the Warm Pool is thus crucial to understand and to monitor within the context of seasonal-to-interannual climate variations. The analysis of satellite-based ocean color data shows that low concentrations of surface chlorophyll-a found in the equatorial region of the Pacific Ocean varies in phase with the eastern edge of the western Pacific Warm Pool. As is true for high sea surface temperatures, the existence and maintenance of these low concentrations are linked to the upper ocean stratification due to salinity. The present study also establishes the quasi permanence of a frontal zone in chlorophyll-a separating the regimes of the western region and the eastern-central cold tongue and, through the identification of this front in satellite-based ocean color data, it provides, for the first time, a reliable method for locating the eastern edge of the Warm Pool from surface observations only. Finally, the recognition of this front offers the opportunity to define a simple and robust index of the horizontal extension of the western Pacific Warm Pool within the context of ENSO variability. These results suggest that coupled models used for El Nino research and forecasting should be able to reproduce these important features.
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Detection of the Eastern Edge of the Equatorial Pacific Warm Pool Using Satellite-Based Ocean Color Observations
SOLA, 2010Co-Authors: Christophe Maes, Joël Sudre, Véronique GarçonAbstract:The analysis of satellite-based ocean color data shows that low concentrations of surface chlorophyll-a (chl-a) found in the equatorial region of the Pacific Ocean varies in phase with the eastern edge of the Warm Pool. As is true for high sea surface temperatures, the existence and maintenance of these low concentrations are linked to the upper ocean stratification due to salinity. The present study also establishes the quasi permanence of a frontal zone in chlorophyll-a separating the regimes of the western region and the eastern-central cold tongue and, through the identification of this front in satellite-based ocean color data, it provides, for the first time, a reliable method for locating the eastern edge of the Warm Pool from surface observations only. Finally, the recognition of this front offers the opportunity to define a simple and robust index of the horizontal extension of the equatorial Pacific Warm Pool within the context of the ENSO variability.
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Observed correlation of surface salinity, temperature and barrier layer at the eastern edge of the western Pacific Warm Pool
Geophysical Research Letters, 2006Co-Authors: Christophe Maes, Kentaro Ando, Thierry Delcroix, William S. Kessler, Michael J. Mcphaden, Dean RoemmichAbstract:[1] Recent theory suggests that ocean-atmosphere interactions in the western Pacific Warm Pool are of fundamental importance to interannual variations associated with El Nino and the Southern Oscillation (ENSO). The Warm Pool encompasses the highest mean sea surface temperatures (SSTs) in the world ocean, intense atmospheric deep convection and heavy rainfall, and the formation of thick salt-stratified barrier layers that help to sustain the high SSTs. This study shows that the eastern edge of the Warm Pool is characterized by a strong zonal salinity front throughout 2002–2004. The analysis also indicates a tighter empirical relationship than previously observed between the eastern edge of the Warm Pool, high SSTs, the presence of barrier layers, and the fetch of westerly wind bursts. These results suggest that such a frontal region is a critical in controlling ocean-atmosphere interactions in the western Pacific Warm Pool and highlight the importance of the upper ocean salinity in climate variability.
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Characteristics of the convergence zone at the eastern edge of the Pacific Warm Pool
Geophysical Research Letters, 2004Co-Authors: Christophe Maes, Joël Picaut, Yoshifumi Kuroda, Kentaro AndoAbstract:[1] The characteristics of the convergence zone at the eastern edge of the equatorial Pacific Warm Pool are studied using a compilation of in-situ current and salinity measurements during the period 1992–2001. The displacement of the convergence zone is observed, for the first time, as far west as 140°E in the far western Pacific, mainly during La Nina periods, and near 140°W in the central Pacific during the 1997–98 El Nino. The convergence zone may be associated with a salinity front dividing the fresh waters of the Warm Pool from the salty waters upwelled in the central equatorial Pacific. Despite a zonal displacement ranging over about one fifth of the equatorial circumference of the earth, the characteristics of the main parameters involved in the air-sea interactions are nearly constant on each side of the convergence zone/salinity front. These results suggest that coupled models used for El Nino research and forecasting should be able to reproduce these important features.
Sang-ki Lee - One of the best experts on this subject based on the ideXlab platform.
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What drives the seasonal onset and decay of the Western Hemisphere Warm Pool
Journal of Climate, 2007Co-Authors: Sang-ki Lee, David B Enfield, Chunzai WangAbstract:The annual heat budget of the Western Hemisphere Warm Pool (WHWP) is explored using the output of an ocean general circulation model (OGCM) simulation. According to the analysis, the WHWP cannot be considered as a monolithic whole with a single set of dominating processes that explain its behavior. The three regions considered, namely the eastern north Pacific (ENP), the Gulf of Mexico (GoM), and the Caribbean Sea (CBN), are each unique in terms of the atmospheric and oceanic processes that dominate the corresponding heat budgets. In the ENP region, clear-sky shortwave radiation flux is responsible for the growth of the Warm Pool in boreal spring, while increased cloud cover in boreal summer and associated reduction in solar radiation play a crucial role for the ENP Warm Pool’s demise. Ocean upwelling in the Costa Rica Dome connected to surrounding areas by horizontal advection offers a persistent yearlong cooling mechanism. Over the Atlantic, the clear-sky radiation flux that increases monotonically from December to May and decreases later is largely responsible for the onset and decay of the Atlantic-side Warm Pool in boreal summer and fall. The CBN region is affected by upwelling and horizontal advective cooling within and away from the coastal upwelling zone off northern South America during the onset and peak phases, thus slowing down the Warm Pool’s development, but no evidence was found that advective heat flux divergence is important in the GoM region. Turbulent mixing is also an important cooling mechanism in the annual cycle of the WHWP, and the vertical shear at the Warm Pool base helps to sustain the turbulent mixing. Common to all three WHWP regions is the reduction of wind speed at the peak phase, suggestive of a convection–evaporation feedback known to be important in the Indo-Pacific Warm Pool dynamics.
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The Heat Balance of the Western Hemisphere Warm Pool
Journal of Climate, 2005Co-Authors: David B Enfield, Sang-ki LeeAbstract:The thermodynamic development of the Western Hemisphere Warm Pool and its four geographic subregions are analyzed. The subregional Warm Pools of the eastern North Pacific and equatorial Atlantic are best developed in the boreal spring, while in the Gulf of Mexico and Caribbean, the highest temperatures prevail during the early and late summer, respectively. For the defining isotherms chosen ( >= 27.5 degrees, >= 28.0 degrees, >= 28.5 degrees C) the Warm Pool depths are similar to the mixed-layer depth (20-40 m) but are considerably less than the Indo-Pacific Warm Pool depth (50-60 m). The beat balance of the WHWP subregions is examined through two successive types of analysis: first by considering a changing volume ("bubble") bounded by constant temperature wherein advective fluxes disappear and diffusive fluxes can be estimated as a residual, and second by considering a slab layer of constant dimensions with the bubble diffusion estimates as an additional input and the advective heat flux divergence as a residual output. From this sequential procedure it is possible to disqualify as being physically inconsistent four of seven surface heat flux climatologies: the NCEP-NCAR reanalysis (NCEP1) and the ECMWF 15-yr global reanalysis (ERA-15) because they yield a nonphysical diffusion of heat into the Warm Pools from their cooler surroundings, and the unconstrained da Silva and Southampton datasets because their estimated diffusion rates are inconsistent with the smaller rates of the better understood Indo-Pacific Warm Pool when the bubble analysis is applied to both regions. The remaining surface flux datasets of da Silva and Southampton (constrained) and Oberhuber have a much narrower range of slab surface Warming (+25 +/- 5 W m(-2)) associated with bubble residual estimates of total diffusion of -5 to -20 W m(-2) (-5 W m(-2)) and total advective heat flux divergence of -2 to -14 W m(-2) (+/- 5 W m(-2)). The latter are independently confirmed by direct estimates using wind stress data and drifters for the Gulf of Mexico and eastern North Pacific subregions.
Tim Li - One of the best experts on this subject based on the ideXlab platform.
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Role of the western hemisphere Warm Pool in climate variability over the western North Pacific
Climate Dynamics, 2019Co-Authors: Jae-heung Park, Jong-seong Kug, Soon-il An, Tim LiAbstract:The climate variability in the Western North Pacific (WNP), which is surrounded by densely populated countries, is closely tied to the lives of the people in the East Asia in terms of climate and socioeconomics. Along with global Warming, remarkable interannual and interdecadal variations in sea surface temperature (SST) and sea surface height have been observed in the WNP. Here we demonstrated that boreal summer SST variability in the western hemisphere Warm Pool (WHWP, a.k.a. Atlantic Warm Pool) near the Intra-Americas Sea, which is known as the second largest Warm Pool on the planet, has considerably contributed to the climate variability in the WNP in subsequent winter. This is possible due to westward propagation of Rossby waves associated with a WHWP-SST Warming (cooling) in mid-summer to early fall season, which induces northerly (southerly) wind anomalies over the North Pacific. In the presence of northeasterly mean trade winds, the anomalous meridional winds interact with SST and precipitation anomalies. Such air-sea coupling processes gradually move equatorward and westward along the climatological migration of the Pacific Intertropical Convergence Zone, and it has finally an effect on the climate variability over the WNP in winter. Further diagnosis verifies that WHWP-WNP connection exists not only on interannual time scale but also on decadal time scale. The analysis using state-of-the-art climate models reasonably supports this argument. A better understanding of the WHWP influence is expected to improve forecasts for the WNP climate and assist socioeconomic development in the East Asia.