scholarly journals A Coupled Air–Sea Response Mechanism to Solar Forcing in the Pacific Region

2008 ◽  
Vol 21 (12) ◽  
pp. 2883-2897 ◽  
Author(s):  
Gerald A. Meehl ◽  
Julie M. Arblaster ◽  
Grant Branstator ◽  
Harry van Loon
Keyword(s):  
Climate Model ◽  
Tropical Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Pacific Region ◽  
Solar Forcing ◽  
Coupled Models ◽  
The Pacific ◽  
Precipitation Regimes ◽  
The Tropical Pacific

Abstract The 11-yr solar cycle [decadal solar oscillation (DSO)] at its peaks strengthens the climatological precipitation maxima in the tropical Pacific during northern winter. Results from two global coupled climate model ensemble simulations of twentieth-century climate that include anthropogenic (greenhouse gases, ozone, and sulfate aerosols, as well as black carbon aerosols in one of the models) and natural (volcano and solar) forcings agree with observations in the Pacific region, though the amplitude of the response in the models is about half the magnitude of the observations. These models have poorly resolved stratospheres and no 11-yr ozone variations, so the mechanism depends almost entirely on the increased solar forcing at peaks in the DSO acting on the ocean surface in clear sky areas of the equatorial and subtropical Pacific. Mainly due to geometrical considerations and cloud feedbacks, this solar forcing can be nearly an order of magnitude greater in those regions than the globally averaged solar forcing. The mechanism involves the increased solar forcing at the surface being manifested by increased latent heat flux and evaporation. The resulting moisture is carried to the convergence zones by the trade winds, thereby strengthening the intertropical convergence zone (ITCZ) and the South Pacific convergence zone (SPCZ). Once these precipitation regimes begin to intensify, an amplifying set of coupled feedbacks similar to that in cold events (or La Niña events) occurs. There is a strengthening of the trades and greater upwelling of colder water that extends the equatorial cold tongue farther west and reduces precipitation across the equatorial Pacific, while increasing precipitation even more in the ITCZ and SPCZ. Experiments with the atmosphere component from one of the coupled models are performed in which heating anomalies similar to those observed during DSO peaks are specified in the tropical Pacific. The result is an anomalous Rossby wave response in the atmosphere and consequent positive sea level pressure (SLP) anomalies in the North Pacific extending to western North America. These patterns match features that occur during DSO peak years in observations and the coupled models.

A Lagged Warm Event–Like Response to Peaks in Solar Forcing in the Pacific Region

2009 ◽  
Vol 22 (13) ◽  
pp. 3647-3660 ◽  
Author(s):  
Gerald A. Meehl ◽  
Julie M. Arblaster
Keyword(s):  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Forced Response ◽  
Pacific Region ◽  
Solar Forcing ◽  
Cold Event ◽  
Warm Event ◽  
The Pacific ◽  
The Tropical Pacific

Abstract The forced response coincident with peaks in the 11-yr decadal solar oscillation (DSO) has been shown to resemble a cold event or La Niña–like pattern during December–February (DJF) in the Pacific region in observations and two global coupled climate models. Previous studies with filtered observational and model data have indicated that there could be a lagged warm event or El Niño–like response following the peaks in the DSO forcing by a few years. Here, observations and two climate model simulations are examined, and it is shown that dynamical coupled processes initiated by the response in the tropical Pacific to peaks in solar forcing produce wind-forced ocean Rossby waves near 5°N and 5°S. These reflect off the western boundary, producing downwelling equatorial Kelvin waves that contribute to transitioning the tropical Pacific to a warm event or El Niño–like pattern that lags the peaks in solar forcing by a few years.

scholarly journals Evaluation of the Impact of Argo Data on Ocean Reanalysis in the Pacific Region

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Xuefeng Zhang ◽  
Chaohui Sun ◽  
Chang Liu ◽  
Lianxin Zhang ◽  
Caixia Shao ◽  
...  
Keyword(s):  
Data Assimilation ◽  
General Circulation ◽  
Tropical Pacific ◽  
Northwest Pacific ◽  
Pacific Region ◽  
Ocean Reanalysis ◽  
Argo Data ◽  
The Pacific ◽  
The Impact ◽  
The Tropical Pacific

Observing System Simulation Experiments (OSSEs) have been conducted to evaluate the effect of Argo data assimilation on ocean reanalysis in the Pacific region. The “truth” is obtained from a 5-year model integration from 2003 to 2007 based on the MIT general circulation model with the truly varying atmospheric forcing. The “observations” are the projections of the truth onto the observational network including ocean station data, CTD, and various BTs and Argo, by adding white noise to simulate observational errors. The data assimilation method employed is a sequential three-dimensional variational (3D-Var) scheme within a multigrid framework. Results show the interannual variability of temperature, salinity, and current fields can be reconstructed fairly well. The spread of temperature anomalies in the tropical Pacific region is also able to be reflected accurately when Argo data is assimilated, which may provide a reliable initial field for the forecast of temperature and currents for the subsurface in the tropical Pacific region. The adjustment of salinity by using T-S relationship is vital in the tropical Pacific region. However, the adjustment of salinity is almost meaningless in the northwest Pacific if Argo data is included during the reanalysis.

Pacific Meridional Modes without Equatorial Pacific Influence

2021 ◽  
pp. 1-51
Author(s):  
Yu Zhang ◽  
Shiyun Yu ◽  
Dillon J. Amaya ◽  
Yu Kosaka ◽  
Sarah M. Larson ◽  
...  
Keyword(s):  
North Pacific ◽  
Climate Model ◽  
Decadal Variability ◽  
Model Simulation ◽  
Southern Oscillation ◽  
South Pacific ◽  
Tropical Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Atmospheric Teleconnections

AbstractInvestigating Pacific Meridional Modes (PMM) without the influence of tropical Pacific variability is technically difficult if based on observations or fully coupled model simulations due to their overlapping spatial structures. To confront this issue, the present study investigates both North (NPMM) and South PMM (SPMM) in terms of their associated atmospheric forcing and response processes based on a mechanically decoupled climate model simulation. In this experiment, the climatological wind stress is prescribed over the tropical Pacific, which effectively removes dynamically coupled tropical Pacific variability (e.g., the El Niño-Southern Oscillation). Interannual NPMM in this experiment is forced not only by the North Pacific Oscillation, but also by a North Pacific tripole (NPT) pattern of atmospheric internal variability, which primarily forces decadal NPMM variability. Interannual and decadal variability of the SPMM is partly forced by the South Pacific Oscillation. In turn, both interannual and decadal NPMM variability can excite atmospheric teleconnections over the Northern Hemisphere extratropics by influencing the meridional displacement of the climatological intertropical convergence zone throughout the whole year. Similarly, both interannual and decadal SPMM variability can also excite atmospheric teleconnections over the Southern Hemisphere extratropics by extending/shrinking the climatological South Pacific convergence zone in all seasons. Our results highlight a new poleward pathway by which both the NPMM and SPMM feed back to the extratropical climate, in addition to the equatorward influence on tropical Pacific variability.

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.

Rattus exulans (Pacific rat).

2021 ◽  
Author(s):  
Aaron Shiels
Keyword(s):  
Southeast Asia ◽  
Bird Species ◽  
Tropical Pacific ◽  
Pacific Basin ◽  
The Past ◽  
The Pacific ◽  
Ground Nesting ◽  
The Tropical Pacific

Abstract The Pacific rat, R. exulans, is an major agricultural and environmental pest in parts of Southeast Asia and the Pacific. Thought to have spread with Polynesian colonists over the past several thousand years, it is now found through much of the Pacific basin, and is extensively distributed in the tropical Pacific. It poses a significant threat to indigenous wildlife, particularly ground-nesting birds, and has been linked to the extinction of several bird species. R. exulans may also transmit diseases to humans.

Reconstructing an Interdecadal Pacific Oscillation Index from a Pacific Basin–Wide Collection of Ice Core Records

2021 ◽  
Vol 34 (10) ◽  
pp. 3839-3852
Author(s):  
Stacy E. Porter ◽  
Ellen Mosley-Thompson ◽  
Lonnie G. Thompson ◽  
Aaron B. Wilson
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Tropical Pacific ◽  
Ice Age ◽  
Pacific Basin ◽  
Interdecadal Pacific Oscillation ◽  
The Pacific ◽  
Instrumental Period ◽  
The Tropical Pacific ◽  
Ice Core Records

AbstractUsing an assemblage of four ice cores collected around the Pacific basin, one of the first basinwide histories of Pacific climate variability has been created. This ice core–derived index of the interdecadal Pacific oscillation (IPO) incorporates ice core records from South America, the Himalayas, the Antarctic Peninsula, and northwestern North America. The reconstructed IPO is annually resolved and dates to 1450 CE. The IPO index compares well with observations during the instrumental period and with paleo-proxy assimilated datasets throughout the entire record, which indicates a robust and temporally stationary IPO signal for the last ~550 years. Paleoclimate reconstructions from the tropical Pacific region vary greatly during the Little Ice Age (LIA), although the reconstructed IPO index in this study suggests that the LIA was primarily defined by a weak, negative IPO phase and hence more La Niña–like conditions. Although the mean state of the tropical Pacific Ocean during the LIA remains uncertain, the reconstructed IPO reveals some interesting dynamical relationships with the intertropical convergence zone (ITCZ). In the current warm period, a positive (negative) IPO coincides with an expansion (contraction) of the seasonal latitudinal range of the ITCZ. This relationship is not stationary, however, and is virtually absent throughout the LIA, suggesting that external forcing, such as that from volcanoes and/or reduced solar irradiance, could be driving either the ITCZ shifts or the climate dominating the ice core sites used in the IPO reconstruction.

scholarly journals Impact of Resolution on the Tropical Pacific Circulation in a Matrix of Coupled Models

2009 ◽  
Vol 22 (10) ◽  
pp. 2541-2556 ◽  
Author(s):  
Malcolm J. Roberts ◽  
A. Clayton ◽  
M.-E. Demory ◽  
J. Donners ◽  
P. L. Vidale ◽  
...  
Keyword(s):  
Coupled Model ◽  
Walker Circulation ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Coupled Models ◽  
Model Stability ◽  
The Mean ◽  
The Impact ◽  
Mean State ◽  
The Tropical Pacific

Abstract Results are presented from a matrix of coupled model integrations, using atmosphere resolutions of 135 and 90 km, and ocean resolutions of 1° and 1/3°, to study the impact of resolution on simulated climate. The mean state of the tropical Pacific is found to be improved in the models with a higher ocean resolution. Such an improved mean state arises from the development of tropical instability waves, which are poorly resolved at low resolution; these waves reduce the equatorial cold tongue bias. The improved ocean state also allows for a better simulation of the atmospheric Walker circulation. Several sensitivity studies have been performed to further understand the processes involved in the different component models. Significantly decreasing the horizontal momentum dissipation in the coupled model with the lower-resolution ocean has benefits for the mean tropical Pacific climate, but decreases model stability. Increasing the momentum dissipation in the coupled model with the higher-resolution ocean degrades the simulation toward that of the lower-resolution ocean. These results suggest that enhanced ocean model resolution can have important benefits for the climatology of both the atmosphere and ocean components of the coupled model, and that some of these benefits may be achievable at lower ocean resolution, if the model formulation allows.

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