scholarly journals Observed Warm Filaments from the Kuroshio Associated with Mesoscale Eddies

2020 ◽  
Vol 12 (18) ◽  
pp. 3090
Author(s):  
Qian Shi ◽  
Guihua Wang
Keyword(s):  
High Frequency ◽  
Average Length ◽  
Mesoscale Eddies ◽  
Satellite Observations ◽  
Sea Surface ◽  
Large Temperature ◽  
Anticyclonic Eddies ◽  
The Kuroshio ◽  
Sst Gradient

Based on high resolution satellite observations of sea surface temperature (SST), warm filaments near the Kuroshio around the Luzon Strait were systematically identified. These filaments extend an average length of about 200 km from the Kuroshio. The occurrence and features of the warm filaments are highly associated with both mesoscale eddies and the intensity of the SST gradient of the Kuroshio. Warm filaments are formed by heat advection from the warm Kuroshio into the colder interior Pacific Ocean by anticyclonic eddies (∼58%), cyclonic eddies (∼10%), and the dipole eddies (∼16%). The large temperature gradient near the Batanes Islands may also contribute to the high frequency of warm filaments in their vicinity. This study will help elucidate the role of zonal heat transport associated with the Kuroshio–eddy interaction during filament formation.

scholarly journals The Role of Back Pressure in the Atmospheric Response to Surface Stress Induced by the Kuroshio

2017 ◽  
Vol 74 (2) ◽  
pp. 597-615 ◽  
Author(s):  
Kohei Takatama ◽  
Niklas Schneider
Keyword(s):  
Boundary Layer ◽  
Wind Stress ◽  
Back Pressure ◽  
Ocean Currents ◽  
Sea Surface ◽  
Ocean Current ◽  
Wind Stress Curl ◽  
General Response ◽  
The Kuroshio

Abstract The effect of ocean current drag on the atmosphere is of interest as a test case for the role of back pressure, because the response is independent of the thermally induced modulation of the boundary layer stability and hydrostatic pressure. The authors use a regional atmospheric model to investigate the impact of drag induced by the Kuroshio in the East China Sea on the overlying winter atmosphere. Ocean currents dominate the wind stress curl compared to the impacts of sea surface temperature (SST) fronts. Wind stress convergences and divergences are weakly enhanced even though the ocean current is almost geostrophic. These modifications change the linear relationships (coupling coefficients) between the wind stress curl/divergence and the SST Laplacian, crosswind, and downwind gradients. Clear signatures of the ocean current impacts are found beyond the sea surface: sea surface pressure (back pressure) decreases near the current axis, and precipitation increases over the downwind region. However, these responses are very small despite strong Ekman pumping due to the current. A linear reduced gravity model is used to explain the boundary layer dynamics. The linear vorticity equation shows that the oceanic influence on wind stress curl is balanced by horizontal advection decoupling the boundary layer from the interior atmosphere. Spectral transfer functions are used to explain the general response of back pressure to geostrophic ocean currents and sea surface height.

scholarly journals Energy Exchange between the Mesoscale Oceanic Eddies and Wind-Forced Near-Inertial Oscillations

2017 ◽  
Vol 47 (3) ◽  
pp. 721-733 ◽  
Author(s):  
Zhao Jing ◽  
Lixin Wu ◽  
Xiaohui Ma
Keyword(s):  
Energy Transfer ◽  
Energy Exchange ◽  
Kuroshio Extension ◽  
Mesoscale Eddies ◽  
Energy Transfer Efficiency ◽  
Layer Model ◽  
Strain Variance ◽  
Anticyclonic Eddies ◽  
The Kuroshio ◽  
Kuroshio Extension Region

AbstractIn this study, the energy exchange between mesoscale eddies and wind-forced near-inertial oscillations (NIOs) is theoretically analyzed using a slab mixed layer model modified by including the geostrophic flow. In the presence of strain, there is a permanent energy transfer from mesoscale eddies to NIOs forced by isotropic wind stress. The energy transfer efficiency, that is, the ratio of the energy transfer rate to the near-inertial wind work, is proportional to , where S2 is the total strain variance, is the effective Coriolis frequency, and ζ is the relative vorticity. The theories derived from the modified slab mixed layer model are verified by the realistic numerical simulation obtained from a coupled regional climate model (CRCM) configured over the North Pacific. Pronounced energy transfer from mesoscale eddies to wind-forced NIOs is localized in the Kuroshio Extension region associated with both strong near-inertial wind work and strain variance. The energy transfer efficiency in anticyclonic eddies is about twice the value in cyclonic eddies in the Kuroshio Extension region because of the influence of ζ on feff, which may contribute to shaping the dominance of cyclonic eddies than anticyclonic eddies in that region.

scholarly journals Marine Heatwave of Sea Surface Temperature of the Oyashio Region in Summer in 2010–2016

2021 ◽  
Vol 7 ◽  
Author(s):  
Toru Miyama ◽  
Shoshiro Minobe ◽  
Hanako Goto
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Kuroshio Extension ◽  
Sea Surface ◽  
Boreal Summer ◽  
Ocean Reanalysis ◽  
Oyashio Region ◽  
Seriola Quinqueradiata ◽  
Anticyclonic Eddies ◽  
The Kuroshio

The sea surface temperature (SST) of the Oyashio region in boreal summer abruptly increased in 2010 and high summertime SST repeated every year until 2016. Observations and an ocean reanalysis show that this marine heatwave occurred not only at the surface but also at deeper depths down to 200 m. Furthermore, salinity in summer also increased in parallel with the temperature. The rises in temperature and salinity indicate the strengthening of the Kuroshio water influence. The sea surface height and velocity show that the southward intrusion of the Oyashio near the coast in summer weakened from 2010 accompanied by an increase in anticyclonic eddies from the Kuroshio Extension. The much more frequent existence of anticyclonic eddies to the east of the first intrusion of the Oyashio in summer is closely associated with the weakening of the first intrusion and the strengthening of the second intrusion. It is suggested that the rise in the water temperature could increase a catch of yellowtail (Seriola quinqueradiata) in northern Japan.

scholarly journals Effects of Mesoscale Eddies On Intraseasonal Variability of Intermediate Water East of Taiwan

2022 ◽  
Author(s):  
Qiang Ren ◽  
Fei Yu ◽  
Feng Nan ◽  
Yuanlong Li ◽  
Jianfeng Wang ◽  
...  
Keyword(s):  
Intermediate Layer ◽  
Intraseasonal Variability ◽  
Correlation Coefficients ◽  
Mesoscale Eddies ◽  
Vertical Movement ◽  
Intermediate Water ◽  
Sea Level Anomalies ◽  
Anticyclonic Eddies ◽  
Counter Current ◽  
The Kuroshio

Abstract The variability of intermediate water (IW) east of Taiwan was investigated utilizing 17 months of long-term, continuous and synchronous measurements of temperature, salinity and current from mooring sites deployed at 122ºE/23ºN from January 2016 to May 2017. For the first time, we prove that the intraseasonal variability in the IW within significant periods of ~80 days was caused by mesoscale eddies propagating westward from the Subtropic Counter Current (STCC) area. The correlation coefficients between sea level anomalies (SLAs) and the Kuroshio, and between SLAs and the minimum salinity in the intermediate layer, were 0.63 and 0.52, respectively. The anticyclonic (cyclonic) eddies from the STCC, increased (decreased) the speed of the Kuroshio as well as increase (decrease) the temperature and salinity in the 400–600 m in east of Taiwan. Combines Archiving, Validation and Interpretation of Satellite Oceanographic (AVISO) products data, showed that temperature and salinity increased (decreased) in the intermediate layer due to the downward (upward) vertical movement of the water mass by anticyclonic (cyclonic) eddies. Anticyclonic eddies strengthened the Kuroshio and benefitted SCSIW flowing through the Luzon Strait to enhance salinity, while cyclonic eddies weakened the Kuroshio and favored relatively low-salt NPIW, in the area east of Taiwan.

scholarly journals The Role of Background Wind and Moisture in the Atmospheric Response to Oceanic Eddies During Winter in the Kuroshio Extension Region

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 527
Author(s):  
Yinglai Jia ◽  
Longjing Chen ◽  
Qinyu Liu ◽  
Xiaohui Yang ◽  
Yifei Wu
Keyword(s):  
Boundary Layer ◽  
Kuroshio Extension ◽  
Vertical Motion ◽  
Sea Surface ◽  
Initial Condition ◽  
Atmospheric Response ◽  
Background Wind ◽  
Oceanic Eddies ◽  
The Kuroshio

The role of background wind and moisture in the atmospheric response to oceanic eddies during winter in the Kuroshio Extension (KE) region is examined by numerical experiments (EXPs) using the Weather Research and Forecasting (WRF) model. We designed two sets of parallel experiments (dry and wet EXPs). The dry EXPs exclude the moisture in the air and the evaporation process. Each experiment differs only in the background wind speed during the initial condition. The wet EXPs include humidity in the initial condition and evaporation during the integration; the other settings are the same as the dry EXPs. The atmosphere in the two sets of EXPs are forced by the same mesoscale sea surface temperature anomaly which resembles the oceanic warm eddy in KE region. The results of these EXPs confirm that under weak background wind conditions, the atmospheric secondary circulation over oceanic eddies is driven by the pressure adjustment process due to weak advection. In the case of the dry run, the increase in background wind enhances the sea surface wind (SSW) by increasing vertical mixing. The convergence of SSW induces vertical motion and heating in the boundary layer, which further decreases the instability. The atmospheric secondary circulation in the dry run remains within the boundary layer. In wet EXPs, the atmospheric response is similar to that in dry runs when the background wind is very weak. When the background wind speed is increased to the climatology value (in KE region) or higher, the vertical motion triggers the precipitation process and diabatic heating above the boundary layer, and the heating in turn reinforces the upward flow.

scholarly journals Satellite Observations of Typhoon-Induced Sea Surface Temperature Variability in the Upwelling Region off Northeastern Taiwan

2020 ◽  
Vol 12 (20) ◽  
pp. 3321
Author(s):  
Yi-Chun Kuo ◽  
Ming-An Lee ◽  
Yi Chang
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Numerical Models ◽  
Kuroshio Current ◽  
Taiwan Strait ◽  
Satellite Observations ◽  
Sea Surface ◽  
Subsurface Water ◽  
Ekman Pumping ◽  
The Kuroshio

Typhoon-induced cooling in the cold dome region off northeastern Taiwan has a major influence on ocean biogeochemistry. It has previously been studied using numerical models and hydrographic observations. Strong cooling is related to upwelling of the Kuroshio subsurface water accompanied by the westward intrusion of the continental shelf by Kuroshio water. By employing satellite observations, local measurements, and a reanalysis of model data, this study compared 18 typhoon-induced sea surface temperature (SST) responses in the cold dome region and determined that SST responses can differ dramatically depending on the relative location of a typhoon path, the Kuroshio Current, and the topography off northeastern Taiwan. The results indicated that local westward and northward wind stress is positively correlated with upwelling intensity. Decreased northward transport in the Taiwan Strait created a condition that favored the Kuroshio intrusion, thus, the typhoon-induced change in Taiwan Strait transport was also positively correlated with the intensity of cooling. However, the strength of Ekman pumping was weakly correlated with the intensity of SST cooling. Nevertheless, Ekman pumping helped reduce the cover of warm water, facilitating the intrusion of the Kuroshio Current.

scholarly journals Multi-Source Data Analysis of Mesoscale Eddies and Their Effects on Surface Chlorophyll in the Bay of Bengal

2020 ◽  
Vol 12 (21) ◽  
pp. 3485
Author(s):  
Xiao Yang ◽  
Guangjun Xu ◽  
Yu Liu ◽  
Wenjin Sun ◽  
Changshui Xia ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Bay Of Bengal ◽  
Cold Water ◽  
Mesoscale Eddies ◽  
Sea Surface ◽  
Wind Fields ◽  
Local Current ◽  
Source Data ◽  
Eddy Generation ◽  
Anticyclonic Eddies

Mesoscale eddies are important to ocean circulation due to their roles in the transport of mass, energy, and heat. This study employs a combination of data sources to initiate a statistical analysis of eddy spatiotemporal characteristics in the Bay of Bengal (BOB) to elucidate the sea surface and vertical structures of the eddies and their impacts on sea surface chlorophyll (Chl) distributions. The results suggest that 1237 cyclonic eddies (CEs) and 1121 anticyclonic eddies (AEs) were detected in 26 years. The number of two eddy polarities was almost the same, and most of them spread to the west or southwest direction. The vertical change of temperature (T) and salinity (S) caused by the eddies is studied and the anomalous eddies, i.e., a CE (AE) eddy with warm (cold) water at the center, are mainly distributed on the northeast side of the Island of Sri Lanka. Furthermore, CEs are found to increase Chl concentration in the surrounding sea by approximately 11.15%, while AEs decrease concentrations also by approximately 11.25%. Changes in Chl concentrations occur most rapidly during the mature and intensification eddy phases. Observations also indicate that the strong local current and wind fields are the primary mechanisms in eddy generation.

scholarly journals Mesoscale SST Dynamics in the Kuroshio–Oyashio Extension Region

2019 ◽  
Vol 49 (5) ◽  
pp. 1339-1352 ◽  
Author(s):  
Zhao Jing ◽  
Ping Chang ◽  
Xuan Shan ◽  
Shengpeng Wang ◽  
Lixin Wu ◽  
...  
Keyword(s):  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Mesoscale Eddies ◽  
Reanalysis Data ◽  
Sea Surface ◽  
Height Anomaly ◽  
Theoretical Expression ◽  
Surface Salinity ◽  
Density Anomaly ◽  
The Kuroshio

Abstract Mesoscale eddies have been extensively studied based on the sea surface height anomaly (SSHA). However, it is the sea surface temperature anomaly (SSTA) that is vital to the mesoscale eddy–atmosphere interactions. In this study, we analyze the amplitude relationship between SSHA and SSTA (referred to as the H-T amplitude relationship) in the Kuroshio–Oyashio extension (KOE) region using both observational and reanalysis data. It is found that the spatial distribution of mesoscale SSHA variance is not coincident with mesoscale SSTA variance. The former peaks in the Kuroshio extension around 35°N whereas the latter is strongest in the Oyashio extension around 40°N. Regression analyses indicate that the rate of SSTA change per SSHA change is 1.8°C m−1 in the Kuroshio extension (145°–160°E, 34°–36°N) but increases drastically by a factor of 3–4 to 6.2°C m−1 in the Oyashio extension (145°–160°E, 39°–41°N). A theoretical expression for the H-T amplitude relationship is derived. Analyzing this expression suggests that the stronger H-T amplitude relationship in the Oyashio extension than the Kuroshio extension is mainly attributed to 1) the smaller thermal expansion coefficient due to the colder background SST, 2) the stronger salinity compensation effect that works against the contribution of SSTA change to sea surface density anomaly (SSDA) change, and 3) the shallower vertical structure of mesoscale eddies. The second factor is ascribed to the strong surface salinity front in the Oyashio extension, while the third factor is found to be qualitatively consistent with the shallower baroclinically unstable modes due to the shallower density front there.

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