Strengthening and Lengthening of the Hawaiian Lee Countercurrent Driven by the Pacific Trade Wind Acceleration

2020 ◽  
Vol 125 (7) ◽  
Author(s):  
Feng Nan ◽  
Huijie Xue ◽  
Fei Yu ◽  
Ran Wang
Keyword(s):  
Trade Wind ◽  
The Pacific ◽  
Hawaiian Lee Countercurrent

scholarly journals Mechanisms of Future Changes in Equatorial Upwelling: CMIP5 Intermodel Analysis

2020 ◽  
Vol 33 (2) ◽  
pp. 497-510 ◽  
Author(s):  
Mio Terada ◽  
Shoshiro Minobe ◽  
Curtis Deutsch
Keyword(s):  
Climate Models ◽  
Eastern Pacific ◽  
Trade Wind ◽  
Pacific Basin ◽  
Ekman Pumping ◽  
Equatorial Atlantic ◽  
Western Atlantic ◽  
Near Surface ◽  
The Pacific ◽  
Equatorial Upwelling

AbstractThe future change in equatorial upwelling between 1971–2000 and 2071–2100 is investigated using data from 24 coupled climate models. The multimodel ensemble (MME) mean exhibits substantial equatorial upwelling decrease in the eastern Pacific and weaker decrease in the western Atlantic Ocean. The MME mean of upwelling change and intermodel variation of that are decomposed into distinct isopycnal and diapycnal components. In the Pacific, the diapycnal upwelling decreases near the surface, associated with a weakened Ekman pumping. The isopycnal upwelling decreases at depths of 75–200 m around the core of the Equatorial Undercurrent (EUC) due to flattening of the density layer in which it flows. Both the weakened Ekman pumping and the EUC flattening are induced by the locally weakened trade wind over the eastern Pacific basin. In the equatorial Atlantic, both the change in MME mean and the intermodel variation of upwellings are significantly related to the weakened trade wind and enhanced stratification, although these drivers are not independent. The results for the Pacific Ocean imply that future reduction in upwelling may have impacts at different depths by different mechanisms. In particular, the rapid warming of sea surface temperature in the eastern Pacific basin may be mainly caused by the near-surface diapycnal upwelling reduction rather than isopycnal upwelling reduction associated EUC flattening, which is important at deeper levels.

Impact of the Pacific mean SST bias to the Atlantic-Pacific teleconnection

2020 ◽  
Author(s):  
Chen Li ◽  
Dietmar Dommenget ◽  
Shayne McGregor
Keyword(s):  
Decadal Variability ◽  
Atmospheric Stability ◽  
Low Frequency ◽  
Trade Wind ◽  
Atmospheric Teleconnection ◽  
Surface Warming ◽  
Sst Bias ◽  
Pacific Decadal Variability ◽  
The Pacific ◽  
Low Frequency Variability

<p><span>A robust eastern tropical Pacific surface temperature cooling trend along with the strengthening of Pacific trade wind is evident across different observations since late 1990s, which is considered as a pronounced contributor to the slowdown in global surface warming. However, most CMIP5 historical simulations failed to reproduce this La Ni</span>ñ<span>a-like change. Previous studies have attributed this discrepancy between the multi-model simulations and the observations to the underrepresentation of Pacific low-frequency variability together with the misrepresentation of inter-basin forcing response. The underlying reasons remain unclear. Here, we investigate a hypothesis that common Pacific mean SST bias may diminish the Pacific-Atlantic atmospheric teleconnection and further contribute to the underestimated eastern Pacific cooling. Model results suggest that the CMIP5-like Pacific bias acts to reduce the Atlantic heating response by strengthening the atmospheric stability over the Atlantic region and therefore weaken the trans-basin variability. In addition, </span>the Pacific bias simulation with a strong SST cold tongue substantially undermined the positive zonal wind feedback, which also contributes to the underestimated Pacific cooling response. Future efforts aim at reducing the model mean state biases may significantly help to improve the simulation skills of the trans-basin teleconnection, Pacific decadal variability, and the associated Pacific dynamics.      </p>

A Note on the FM-CW radar as a remote probe of the pacific trade-wind inversion

1973 ◽  
Vol 4 (1-4) ◽  
pp. 201-209 ◽  
Author(s):  
B. R. Bean ◽  
R. E. McGavin ◽  
B. D. Warner
Keyword(s):  
Trade Wind ◽  
The Pacific ◽  
Trade Wind Inversion ◽  
Cw Radar

Drought variability driven by interannual and decadal teleconnection patterns in monsoon regions of Southeast China 

2021 ◽  
Author(s):  
Kwok Pan Chun ◽  
Qing He ◽  
Bastien Dieppois ◽  
Benjamin Pohl ◽  
Ömer Yetemen ◽  
...  
Keyword(s):  
Coupled Model ◽  
Negative Phase ◽  
Cmip5 Models ◽  
Trade Wind ◽  
Drought Severity ◽  
Southeast China ◽  
Teleconnection Patterns ◽  
The Pacific ◽  
Drought Conditions ◽  
Asian Monsoons

<p>Drought conditions of Southeast China are associated with the sea surface temperature warm pool in the tropical Western Pacific, which is related to low-frequency hydroclimatic patterns and their teleconnections. Empirically, the moisture influx to the region is linked to the interannual and decadal teleconnections, including the Pacific Decadal Oscillation (PDO), the Pacific-Japan Oscillation (PJO) and the Silk Road Pattern (SRP). However, it is still unclear how those teleconnection patterns affect drought conditions in Southeast China via changes in monsoons’ dynamics or wave activities. In this study, we use ERA5 reanalysis over the 1950-2019 period to explore the impacts of the PDO, PJO and SRP on Asian monsoons’ dynamics and regional drought conditions over Southeast China, based on a self-calibrating Palmer Drought Severity Index (scPDSI). We specially use station data from the Greater Bay Area (GBA) which is a national key region for development in Southeast China which is affected by seasonal droughts in winters. Results indicate that drought conditions in Southeast China are significantly related to monsoons: the East Asia Monsoon (EAM), the Western North Pacific Monsoon (WNPM) and the Webster-Yang Monsoon (WYM), between 1950-2019. The strength of monsoons is modulated by PDO, PJO and SRP. A negative phase of SRP corresponds to a southward shift of the Asian westerly jet, strengthening winter Asian monsoons and causing drier conditions in the GBA. Similarly, a cold phase of PDO contributes to drier conditions in the GBA, by weakening Asian monsoons. For the negative phase of PJO, the trade wind of the Walker cell is weakened by the meridional pressure dipole over the West Pacific adjacent to the Southeast China coast. This pressure dipole reduces moisture influx to the continent by the weakened trade wind and leads to less precipitation over East China. Such three climate factors are also interacted through the modulations of monsoons and wave-activities. An extension of the Eliassen-Palm (EP) flux shows that the SRP relates to convective and dynamic wave-activities, which could explain changes in monsoons’ dynamics and drought conditions in Southeast China. To investigate the future drought conditions over Southeast China, bias-corrected historical and RCP8.5 scenarios are used for six of the Coupled Model Intercomparison Project Phase 5 (CMIP5) models (i.e. ACCESS1, BCC, CNRM, IPSL, MPI, and GFDL) between 1861-2100. Among six models, IPSL and GFDL models reproduce the teleconnections well between changes in the monsoons and drought conditions over the GBA, for both historical simulations and future projections. Our results provide insights into the mechanisms of teleconnection patterns affecting drought monitoring and risk management in Southeast China. </p>

scholarly journals Causes of ENSO Weakening during the Mid-Holocene

2017 ◽  
Vol 30 (17) ◽  
pp. 7049-7070 ◽  
Author(s):  
Zhiping Tian ◽  
Tim Li ◽  
Dabang Jiang ◽  
Lin Chen
Keyword(s):  
Large Scale ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Trade Wind ◽  
Thermocline Feedback ◽  
The Pacific ◽  
Project Phases ◽  
Mixed Layer Heat Budget ◽  
Paleoclimate Records ◽  
Underlying Mechanisms

The causes of the change in amplitude of El Niño–Southern Oscillation (ENSO) during the mid-Holocene were investigated by diagnosing the model simulations that participated in the Paleoclimate Modelling Intercomparison Project phases 2 and 3. Consistent with paleoclimate records, 20 out of the 28 models reproduced weaker-than-preindustrial ENSO amplitude during the mid-Holocene. Two representative models were then selected to explore the underlying mechanisms of air–sea feedback processes. A mixed layer heat budget diagnosis indicated that the weakened ENSO amplitude was primarily attributed to the decrease in the Bjerknes thermocline feedback, while the meridional advective feedback also played a role. During the mid-Holocene, the thermocline response to a unit anomalous zonal wind stress forcing in the equatorial Pacific weakened in both models because of the increased ENSO meridional scale. A further investigation revealed that the greater ENSO meridional width was caused by the strengthening of the Pacific subtropical cell, which was attributed to the enhanced mean trade wind that resulted from the intensified Asian and African monsoon rainfall and associated large-scale east–west circulation in response to the mid-Holocene orbital forcing.

scholarly journals Analogous Pacific and Atlantic Meridional Modes of Tropical Atmosphere–Ocean Variability*

2004 ◽  
Vol 17 (21) ◽  
pp. 4143-4158 ◽  
Author(s):  
John C. H. Chiang ◽  
Daniel J. Vimont
Keyword(s):  
Decadal Variability ◽  
Trade Wind ◽  
Tropical Atmosphere ◽  
Tropical Atlantic ◽  
Cold Tongue ◽  
Ocean Variability ◽  
The Pacific ◽  
The Mean ◽  
Meridional Mode ◽  
Subtropical Oceans

Abstract From observational analysis a Pacific mode of variability in the intertropical convergence zone (ITCZ)/cold tongue region is identified that possesses characteristics and interpretation similar to the dominant “meridional” mode of interannual–decadal variability in the tropical Atlantic. The Pacific and Atlantic meridional modes are characterized by an anomalous sea surface temperature (SST) gradient across the mean latitude of the ITCZ coupled to an anomalous displacement of the ITCZ toward the warmer hemisphere. Both are forced by trade wind variations in their respective northern subtropical oceans. The Pacific meridional mode exists independently of ENSO, although ENSO nonlinearity projects strongly on it during the peak anomaly season of boreal spring. It is suggested that the Pacific and Atlantic modes are analogous, governed by physics intrinsic to the ITCZ/ cold tongue complex.

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