SST front anchored mesoscale feature of surface wind in the southern Indian Ocean

2019 ◽  
Vol 53 (1-2) ◽  
pp. 477-490 ◽  
Author(s):  
Xia Huang ◽  
Xuhua Cheng ◽  
Yiquan Qi
Keyword(s):  
Indian Ocean ◽  
Surface Wind ◽  
Southern Indian Ocean ◽  
Sst Front ◽  
Mesoscale Feature

The impact of SST front on the surface wind in the southern Indian Ocean

2020 ◽  
Author(s):  
Xuhua Cheng
Keyword(s):  
Indian Ocean ◽  
Deep Convection ◽  
Surface Wind ◽  
Polar Front ◽  
Open Ocean ◽  
Heat Fluxes ◽  
Southern Indian Ocean ◽  
Sst Front ◽  
Microwave Imager ◽  
The Impact

<p><span> </span>Using 28-year satellite-borne Special Sensor Microwave Imager observations, features of high-wind frequency (HWF) over</p><p>the southern Indian Ocean are investigated. Climatology maps show that high winds occur frequently during austral winter,</p><p>located in the open ocean south of Polar Front in subpolar region, warm flank of the Subantarctic Front between 55<sup>o</sup>E-78<sup>o</sup>E, </p><p>and south of Cape Agulhas, where westerly wind prevails. The strong instability of marine atmospheric boundary layer</p><p>accompanied by increased sensible and latent heat fluxes on the warmer flank acts to enhance the vertical momentum mixing,</p><p>thus accelerate the surface winds. Effects of sea surface temperature (SST) front can even reach the entire troposphere</p><p>by deep convection. HWF also shows distinct interannual variability, which is associated with the Southern Annual Mode</p><p>(SAM). During positive phase of the SAM, HWF has positive anomalies over the open ocean south of Polar Front, while</p><p>has negative anomalies north of the SST front. A phase shift of HWF happened around 2001, which is likely related to the</p><p>reduction of storm tracks and poleward shift of westerly winds in the Southern Hemisphere.</p>

scholarly journals A “Cold Path” for the Gulf Stream–Troposphere Connection

2017 ◽  
Vol 30 (4) ◽  
pp. 1363-1379 ◽  
Author(s):  
Benoît Vannière ◽  
Arnaud Czaja ◽  
Helen Dacre ◽  
Tim Woollings
Keyword(s):  
Boundary Layer ◽  
Gulf Stream ◽  
Surface Wind ◽  
Extratropical Cyclone ◽  
Convective Precipitation ◽  
Dynamical Response ◽  
Sst Front ◽  
Simple Boundary ◽  
Pressure Anomaly ◽  
Sst Gradient

Abstract The mechanism by which the Gulf Stream sea surface temperature (SST) front anchors a band of precipitation on its warm edge is still a matter of debate, and little is known about how synoptic activity contributes to the mean state. In the present study, the influence of the SST front on precipitation is investigated during the course of a single extratropical cyclone using a regional configuration of the Met Office Unified Model. The comparison of a control run with a simulation in which SST gradients were smoothed brought the following conclusions: a band of precipitation is reproduced for a single extratropical cyclone, and the response to the SST gradient is dominated by a change of convective precipitation in the cold sector of the storm. Several climatological features described by previous studies, such as surface wind convergence on the warm edge or a meridional circulation cell across the SST front, are also reproduced at synoptic time scales in the cold sector. Based on these results, a simple boundary layer model is proposed to explain the convective and dynamical response to the SST gradient in the cold sector. In this model, cold and dry air parcels acquire more buoyancy over a sharp SST gradient and become more convectively unstable. The convection sets a pressure anomaly over the entire depth of the boundary layer that drives wind convergence. This case study offers a new pathway by which the SST gradient can anchor a climatological band of precipitation.

Continuous flow analysis of the Mount Brown South ice core

2021 ◽  
Author(s):  
Margaret Harlan ◽  
Helle Astrid Kjær ◽  
Tessa Vance ◽  
Paul Vallelonga ◽  
Vasileios Gkinis ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Size Distribution ◽  
Continuous Flow ◽  
Ice Core ◽  
Flow Analysis ◽  
East Antarctica ◽  
Southern Indian Ocean ◽  
Indian Ocean Region ◽  
Continuous Flow Analysis ◽  
Ocean Region

<p>The Mount Brown South (MBS) ice core is an approximately 300-meter-long ice core, drilled in 2016-2017 to the south of Mount Brown, Wilhelm II Land, East Antarctica. This location in East Antarctica was chosen as it produces an ice core with well-preserved sub-annual records of both chemistry and isotope concentrations, spanning back over 1000 years. MBS is particularly well suited to represent climate variations of the Indian Ocean sector of Antarctica, and to provide information about regional volcanism in the Southern Indian Ocean region.</p><p>A section of ice spanning the length of the MBS core was melted as part of the autumn 2019 continuous flow analysis (CFA) campaign at the Physics of Ice, Climate, and Earth (PICE) group at the University of Copenhagen. During this campaign, measurements were conducted for chemistry and impurities contained in the ice, in addition to water isotopes. The data measured in Copenhagen include measurements of H<sub>2</sub>O<sub>2,</sub> pH, electrolytic conductivity, and NH<sub>4</sub><sup>+</sup>, Ca<sup>2+</sup>, and Na<sup>+</sup> ions, in addition to insoluble particulate concentrations and size distribution measured using an Abakus laser particle counter.</p><p>Here, we present an overview of the CFA chemistry and impurity data, as well as preliminary investigations into the size distribution of insoluble particles and the presence of volcanic material within the ice. These initial chemistry and particulate size distribution data sets are useful in order to identify sections of the MBS core to subject to further analysis to increase our understanding of volcanic activity in the Southern Indian Ocean region.</p>

Formation and Evolution of Microcontinents of the Kerguelen Plateau, Southern Indian Ocean

Geotectonics ◽  
2018 ◽  
Vol 52 (5) ◽  
pp. 499-515 ◽  
Author(s):  
G. L. Leitchenkov ◽  
E. P. Dubinin ◽  
A. L. Grokholsky ◽  
G. D. Agranov
Keyword(s):  
Indian Ocean ◽  
Southern Indian Ocean ◽  
Kerguelen Plateau ◽  
Formation And Evolution

scholarly journals Recent 210 Pb, 137 Cs and 241 Am accumulation in an ombrotrophic peatland from Amsterdam Island (Southern Indian Ocean)

2017 ◽  
Vol 175-176 ◽  
pp. 164-169 ◽  
Author(s):  
Chuxian Li ◽  
Gaël Le Roux ◽  
Jeroen Sonke ◽  
Pieter van Beek ◽  
Marc Souhaut ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Indian Ocean ◽  
Ombrotrophic Peatland

scholarly journals Investigating the Local Atmospheric Response to a Realistic Shift in the Oyashio Sea Surface Temperature Front

2015 ◽  
Vol 28 (3) ◽  
pp. 1126-1147 ◽  
Author(s):  
Dimitry Smirnov ◽  
Matthew Newman ◽  
Michael A. Alexander ◽  
Young-Oh Kwon ◽  
Claude Frankignoul
Keyword(s):  
High Resolution ◽  
Surface Wind ◽  
Lower Troposphere ◽  
Vertical Motion ◽  
Atmospheric Response ◽  
Transient Eddy ◽  
Sst Front ◽  
Moisture Fluxes ◽  
Upper Level ◽  
Heat And Moisture

Abstract The local atmospheric response to a realistic shift of the Oyashio Extension SST front in the western North Pacific is analyzed using a high-resolution (HR; 0.25°) version of the global Community Atmosphere Model, version 5 (CAM5). A northward shift in the SST front causes an atmospheric response consisting of a weak surface wind anomaly but a strong vertical circulation extending throughout the troposphere. In the lower troposphere, most of the SST anomaly–induced diabatic heating is balanced by poleward transient eddy heat and moisture fluxes. Collectively, this response differs from the circulation suggested by linear dynamics, where extratropical SST forcing produces shallow anomalous heating balanced by strong equatorward cold air advection driven by an anomalous, stationary surface low to the east. This latter response, however, is obtained by repeating the same experiment except using a relatively low-resolution (LR; 1°) version of CAM5. Comparison to observations suggests that the HR response is closer to nature than the LR response. Strikingly, HR and LR experiments have almost identical vertical profiles of . However, diagnosis of the diabatic quasigeostrophic vertical pressure velocity (ω) budget reveals that HR has a substantially stronger response, which together with upper-level mean differential thermal advection balances stronger vertical motion. The results herein suggest that changes in transient eddy heat and moisture fluxes are critical to the overall local atmospheric response to Oyashio Front anomalies, which may consequently yield a stronger downstream response. These changes may require the high resolution to be fully reproduced, warranting further experiments of this type with other high-resolution atmosphere-only and fully coupled GCMs.

scholarly journals Diazotroph community and activity in the Southern Indian Ocean

2022 ◽  
Author(s):  
SUBHADEEP CHOWDHURY ◽  
Hugo Berthelot ◽  
Stéphane L'Helguen ◽  
Jean-François Maguer ◽  
Carolin Löscher ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Indian Ocean
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