A shallow thermocline bias in the southern tropical Pacific in CMIP5/6 models linked to double‐ITCZ bias

2021 ◽  
Author(s):  
Maya Samuels ◽  
Ori Adam ◽  
Hezi Gildor
Keyword(s):  
Tropical Pacific ◽  
Double Itcz

scholarly journals Convection Parameterization, Tropical Pacific Double ITCZ, and Upper-Ocean Biases in the NCAR CCSM3. Part II: Coupled Feedback and the Role of Ocean Heat Transport

2010 ◽  
Vol 23 (3) ◽  
pp. 800-812 ◽  
Author(s):  
Guang J. Zhang ◽  
Xiaoliang Song
Keyword(s):  
Surface Energy ◽  
Heat Transport ◽  
Energy Flux ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Ocean Heat Transport ◽  
Surface Energy Flux ◽  
Double Itcz ◽  
Slab Ocean

Abstract This study investigates the coupled atmosphere–ocean feedback and the role of ocean dynamic heat transport in the formation of double ITCZ over the tropical Pacific in the NCAR Community Climate System Model, version 3 (CCSM3) and its alleviation when a revised Zhang–McFarlane (ZM) convection scheme is used. A hierarchy of coupling strategy is employed for this purpose. A slab ocean model is coupled with the atmospheric component of the Community Atmosphere Model, version 3 (CAM3) to investigate the local feedback between the atmosphere and the ocean. It is shown that the net surface energy flux differences in the southern ITCZ region between the revised and original ZM scheme seen in the stand-alone CAM3 simulations can cool the SST by up to 1.5°C. However, the simulated SST distribution is very sensitive to the prescribed ocean heat transport required in the slab ocean model. To understand the role of ocean heat transport, the fully coupled CCSM3 model is used. The analysis of CCSM3 simulations shows that the altered ocean dynamic heat transport when the revised ZM scheme is used is largely responsible for the reduction of SST bias in the southern ITCZ region, although surface energy flux also helps to cool the SST in the first few months of the year in seasonal variation. The results, together with those from Part I, suggest that the unrealistic simulation of convection over the southern ITCZ region in the standard CCSM3 leads to the double-ITCZ bias through complex coupled interactions between atmospheric convection, surface winds, latent heat flux, cloud radiative forcing, SST, and upper-ocean circulations. The mitigation of the double-ITCZ bias using the revised ZM scheme is achieved by altering this chain of interactions.

Growing Coconut Palms in the Pacific Islands: Colliding Knowledge and Values

2020 ◽  
Author(s):  
Judith A. Bennett
Keyword(s):  
Pacific Islands ◽  
Social Values ◽  
Coconut Oil ◽  
Tropical Pacific ◽  
Experiential Knowledge ◽  
The West ◽  
Passive Resistance ◽  
The People ◽  
The Pacific ◽  
The Tropical Pacific

Coconuts provided commodities for the West in the form of coconut oil and copra. Once colonial governments established control of the tropical Pacific Islands, they needed revenue so urged European settlers to establish coconut plantations. For some decades most copra came from Indigenous growers. Administrations constantly urged the people to thin old groves and plant new ones like plantations, in grid patterns, regularly spaced and weeded. Local growers were instructed to collect all fallen coconuts for copra from their groves. For half a century, the administrations’ requirements met with Indigenous passive resistance. This paper examines the underlying reasons for this, elucidating Indigenous ecological and social values, based on experiential knowledge, knowledge that clashed with Western scientific values.

Successive Modulation of ENSO to the Future Greenhouse Warming

2008 ◽  
Vol 21 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Soon-Il An ◽  
Jong-Seong Kug ◽  
Yoo-Geun Ham ◽  
In-Sik Kang
Keyword(s):  
General Circulation ◽  
Southern Oscillation ◽  
General Circulation Models ◽  
Tropical Pacific ◽  
Greenhouse Warming ◽  
Delayed Response ◽  
Subsurface Temperature ◽  
Climate System Model ◽  
The Mean ◽  
The Tropical Pacific

Abstract The multidecadal modulation of the El Niño–Southern Oscillation (ENSO) due to greenhouse warming has been analyzed herein by means of diagnostics of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled general circulation models (CGCMs) and the eigenanalysis of a simplified version of an intermediate ENSO model. The response of the global-mean troposphere temperature to increasing greenhouse gases is more likely linear, while the amplitude and period of ENSO fluctuates in a multidecadal time scale. The climate system model outputs suggest that the multidecadal modulation of ENSO is related to the delayed response of the subsurface temperature in the tropical Pacific compared to the response time of the sea surface temperature (SST), which would lead a modulation of the vertical temperature gradient. Furthermore, an eigenanalysis considering only two parameters, the changes in the zonal contrast of the mean background SST and the changes in the vertical contrast between the mean surface and subsurface temperatures in the tropical Pacific, exhibits a good agreement with the CGCM outputs in terms of the multidecadal modulations of the ENSO amplitude and period. In particular, the change in the vertical contrast, that is, change in difference between the subsurface temperature and SST, turns out to be more influential on the ENSO modulation than changes in the mean SST itself.

scholarly journals Indian Ocean impact on ENSO evolution 2014–2016 in a set of seasonal forecasting experiments

2021 ◽  
Author(s):  
Michael Mayer ◽  
Magdalena Alonso Balmaseda
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
El Niño ◽  
Initial Conditions ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Tropical Pacific ◽  
Decadal Variations ◽  
The Indian Ocean

AbstractThis study investigates the influence of the anomalously warm Indian Ocean state on the unprecedentedly weak Indonesian Throughflow (ITF) and the unexpected evolution of El Niño-Southern Oscillation (ENSO) during 2014–2016. It uses 25-month-long coupled twin forecast experiments with modified Indian Ocean initial conditions sampling observed decadal variations. An unperturbed experiment initialized in Feb 2014 forecasts moderately warm ENSO conditions in year 1 and year 2 and an anomalously weak ITF throughout, which acts to keep tropical Pacific ocean heat content (OHC) anomalously high. Changing only the Indian Ocean to cooler 1997 conditions substantially alters the 2-year forecast of Tropical Pacific conditions. Differences include (i) increased probability of strong El Niño in 2014 and La Niña in 2015, (ii) significantly increased ITF transports and (iii), as a consequence, stronger Pacific ocean heat divergence and thus a reduction of Pacific OHC over the two years. The Indian Ocean’s impact in year 1 is via the atmospheric bridge arising from altered Indian Ocean Dipole conditions. Effects of altered ITF and associated ocean heat divergence (oceanic tunnel) become apparent by year 2, including modified ENSO probabilities and Tropical Pacific OHC. A mirrored twin experiment starting from unperturbed 1997 conditions and several sensitivity experiments corroborate these findings. This work demonstrates the importance of the Indian Ocean’s decadal variations on ENSO and highlights the previously underappreciated role of the oceanic tunnel. Results also indicate that, given the physical links between year-to-year ENSO variations, 2-year-long forecasts can provide additional guidance for interpretation of forecasted year-1 ENSO probabilities.

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