Storminess interannual variability and coastal hazards over the south-western Spanish coast: links to large scale atmospheric forcing

AbstractThe development of coastal polynyas, areas of enhanced heat flux and sea ice production strongly depend on atmospheric conditions. In Antarctica, measurements are scarce and models are essential for the investigation of polynyas. A robust quantification of polynya exchange processes in simulations relies on a realistic representation of atmospheric conditions in the forcing dataset. The sensitivity of simulated coastal polynyas in the south-western Weddell Sea to the atmospheric forcing is investigated with the Finite-Element Sea ice-Ocean Model (FESOM) using daily NCEP/NCAR reanalysis data (NCEP), 6 hourly Global Model Europe (GME) data and two different hourly datasets from the high-resolution Consortium for Small-Scale Modelling (COSMO) model. Results are compared for April to August in 2007–09. The two coarse-scale datasets often produce the extremes of the data range, while the finer-scale forcings yield results closer to the median. The GME experiment features the strongest winds and, therefore, the greatest polynya activity, especially over the eastern continental shelf. This results in higher volume and export of High Salinity Shelf Water than in the NCEP and COSMO runs. The largest discrepancies between simulations occur for 2008, probably due to differing representations of the ENSO pattern at high southern latitudes. The results suggest that the large-scale wind field is of primary importance for polynya development.

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Interannual Variability in the Large-Scale Dynamics of the South Asian Summer Monsoon

Journal of Climate ◽

10.1175/jcli-d-14-00612.1 ◽

2015 ◽

Vol 28 (9) ◽

pp. 3731-3750 ◽

Cited By ~ 22

Author(s):

Jennifer M. Walker ◽

Simona Bordoni ◽

Tapio Schneider

Keyword(s):

Interannual Variability ◽

South Asian ◽

Summer Monsoon ◽

Large Scale ◽

Asian Summer Monsoon ◽

Sea Breeze ◽

South Asian Summer Monsoon ◽

The South ◽

Near Surface ◽

Asian Summer

Abstract This study identifies coherent and robust large-scale atmospheric patterns of interannual variability of the South Asian summer monsoon (SASM) in observational data. A decomposition of the water vapor budget into dynamic and thermodynamic components shows that interannual variability of SASM net precipitation (P − E) is primarily caused by variations in winds rather than in moisture. Linear regression analyses reveal that strong monsoons are distinguished from weak monsoons by a northward expansion of the cross-equatorial monsoonal circulation, with increased precipitation in the ascending branch. Interestingly, and in disagreement with the view of monsoons as large-scale sea-breeze circulations, strong monsoons are associated with a decreased meridional gradient in the near-surface atmospheric temperature in the SASM region. Teleconnections exist from the SASM region to the Southern Hemisphere, whose midlatitude poleward eddy energy flux correlates with monsoon strength. Possible implications of these teleconnection patterns for understanding SASM interannual variability are discussed.

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The South Atlantic Subtropical High: Climatology and Interannual Variability

Journal of Climate ◽

10.1175/jcli-d-16-0705.1 ◽

2017 ◽

Vol 30 (9) ◽

pp. 3279-3296 ◽

Cited By ~ 27

Author(s):

Xiaoming Sun ◽

Kerry H. Cook ◽

Edward K. Vizy

Keyword(s):

Interannual Variability ◽

Annual Cycle ◽

Large Scale ◽

Austral Summer ◽

Southern Annular Mode ◽

South Atlantic ◽

Subtropical High ◽

Interannual Variations ◽

The South ◽

The North

ERA-Interim and JRA-55 reanalysis products are analyzed to document the annual cycle of the South Atlantic subtropical high (SASH) and examine how its interannual variability relates to regional and large-scale climate variability. The annual cycle of the SASH is found to have two peaks in both intensity and size. The SASH is strongest and largest during the solstitial months when its center is either closest to the equator and on the western side of the South Atlantic basin during austral winter or farthest poleward and in the center of the basin in late austral summer. Although interannual variations in the SASH’s position are larger in the zonal direction, the intensity of the high decreases when it is positioned to the north. This relationship is statistically significant in every month. Seasonal composites and EOF analysis indicate that meridional changes in the position of the SASH dominate interannual variations in austral summer. In particular, the anticyclone tends to be displaced poleward in La Niña years when the southern annular mode (SAM) is in its positive phase and vice versa. Wave activity flux vectors suggest that ENSO-related convective anomalies located in the central-eastern tropical Pacific act as a remote forcing for the meridional variability of the summertime SASH. In southern winter, multiple processes operate in concert to induce interannual variability, and none of them appears to dominate like ENSO does during the summer.

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Mesoscale Simulation of Tropical Cyclones in the South Pacific: Climatology and Interannual Variability

Journal of Climate ◽

10.1175/2010jcli3559.1 ◽

2011 ◽

Vol 24 (1) ◽

pp. 3-25 ◽

Cited By ~ 37

Author(s):

Nicolas C. Jourdain ◽

Patrick Marchesiello ◽

Christophe E. Menkes ◽

Jérome Lefèvre ◽

Emmanuel M. Vincent ◽

...

Keyword(s):

Interannual Variability ◽

Tropical Cyclones ◽

Large Scale ◽

Southern Oscillation ◽

Regional Scale ◽

South Pacific ◽

South Pacific Convergence Zone ◽

Dimensional Structure ◽

The South ◽

Wide Range

Abstract The Weather Research and Forecast model at ⅓° resolution is used to simulate the statistics of tropical cyclone (TC) activity in the present climate of the South Pacific. In addition to the large-scale conditions, the model is shown to reproduce a wide range of mesoscale convective systems. Tropical cyclones grow from the most intense of these systems formed along the South Pacific convergence zone (SPCZ) and sometimes develop into hurricanes. The three-dimensional structure of simulated tropical cyclones is in excellent agreement with dropsondes and satellite observations. The mean seasonal and spatial distributions of TC genesis and occurrence are also in good agreement with the Joint Typhoon Warning Center (JTWC) data. It is noted, however, that the spatial pattern of TC activity is shifted to the northeast because of a similar bias in the environmental forcing. Over the whole genesis area, 8.2 ± 3.5 cyclones are produced seasonally in the model, compared with 6.6 ± 3.0 in the JTWC data. Part of the interannual variability is associated with El Niño–Southern Oscillation (ENSO). ENSO-driven displacement of the SPCZ position produces a dipole pattern of correlation and results in a weaker correlation when the opposing correlations of the dipole are amalgamated over the entire South Pacific region. As a result, environmentally forced variability at the regional scale is relatively weak, that is, of comparable order to stochastic variability (±1.7 cyclones yr−1), which is estimated from a 10-yr climatological simulation. Stochastic variability appears essentially related to mesoscale interactions, which also affect TC tracks and the resulting occurrence.

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Basin-Scale Ice Motion and Deformation in the Weddell Sea During Winter

Annals of Glaciology ◽

10.3189/s0260305500007163 ◽

1989 ◽

Vol 12 ◽

pp. 178-186 ◽

Cited By ~ 4

Author(s):

P. Wadhams ◽

C.B. Sear ◽

D.R. Crane ◽

M.A. Rowe ◽

S.J. Morrison ◽

...

Keyword(s):

Large Scale ◽

Weddell Sea ◽

Atmospheric Forcing ◽

Kinematic Parameters ◽

The South ◽

North West ◽

Basin Scale ◽

Maud Rise ◽

Pattern Of Motion

Ice motion in the Weddell Sea is examined for the period 19 August (Day 232) to 12 October (Day 286) 1986 using the tracks of four Argos buoys deployed during the Winter Weddell Sea Project 1986 (WWSP 86). Two were SPRI/BAS buoys, launched in December 1985 and March 1986 in the south-east and north-west Weddell Sea. The others were part of a mesoscale array deployed in the Maud Rise area by H. Hoeber of the Meteorologisches Institut der Universität Hamburg, during the WWSP 86 cruise of FS Polarstern. The four buoys operated together for 44 d, comprising a basin-scale quadrilateral from which the differential kinematic parameters of divergence, vorticity, shear, and stretch were extracted, as well as the large-scale pattern of motion. It is found that most deformation episodes were associated with atmospheric forcing events.

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Relationships between South Atlantic SST Variability and Atmospheric Circulation over the South African Region during Austral Winter

Journal of Climate ◽

10.1175/jcli3474.1 ◽

2005 ◽

Vol 18 (16) ◽

pp. 3339-3355 ◽

Cited By ~ 42

Author(s):

C. J. C. Reason ◽

D. Jagadheesha

Keyword(s):

Interannual Variability ◽

General Circulation ◽

Large Scale ◽

Rainfall Variability ◽

Circulation Model ◽

South Atlantic ◽

The South ◽

Winter Rainfall ◽

Southwest Atlantic ◽

Sst Anomalies

Abstract The Southwestern Cape (SWC) region of South Africa is characterized by winter rainfall brought mainly via cold fronts and by substantial interannual variability. Previous work has found evidence that the interannual variability in SWC winter rainfall may be related to sea surface temperature (SST) in the South Atlantic Ocean and to large-scale ocean–atmosphere interaction in this region. During wet winters, SST tends to be anomalously warm (cool) in the southwest Atlantic and southeast Atlantic (central South Atlantic). Atmospheric general circulation model experiments with various idealized SST anomalies in the South Atlantic are used to explore mechanisms potentially associated with the rainfall variability. The model results suggest that the atmosphere is sensitive to subtropical–midlatitude SST anomalies in the South Atlantic during winter. Locally, there are changes to the jet position and strength, low-level relative vorticity, and convergence of moisture and latent heat flux that lead to changes in rainfall over the SWC. The model response to the SST forcing also shows large-scale anomalies in the midlatitude Southern Hemisphere circulation, namely, an Antarctic Oscillation–type mode and wavenumber-3 changes, similar to those observed during anomalous winters in the region.

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Basin-Scale Ice Motion and Deformation in the Weddell Sea During Winter

Annals of Glaciology ◽

10.1017/s0260305500007163 ◽

1989 ◽

Vol 12 ◽

pp. 178-186 ◽

Cited By ~ 29

Author(s):

P. Wadhams ◽

C.B. Sear ◽

D.R. Crane ◽

M.A. Rowe ◽

S.J. Morrison ◽

...

Keyword(s):

Large Scale ◽

Weddell Sea ◽

Atmospheric Forcing ◽

Kinematic Parameters ◽

The South ◽

North West ◽

Basin Scale ◽

Maud Rise ◽

Pattern Of Motion

Ice motion in the Weddell Sea is examined for the period 19 August (Day 232) to 12 October (Day 286) 1986 using the tracks of four Argos buoys deployed during the Winter Weddell Sea Project 1986 (WWSP 86). Two were SPRI/BAS buoys, launched in December 1985 and March 1986 in the south-east and north-west Weddell Sea. The others were part of a mesoscale array deployed in the Maud Rise area by H. Hoeber of the Meteorologisches Institut der Universität Hamburg, during the WWSP 86 cruise of FS Polarstern. The four buoys operated together for 44 d, comprising a basin-scale quadrilateral from which the differential kinematic parameters of divergence, vorticity, shear, and stretch were extracted, as well as the large-scale pattern of motion. It is found that most deformation episodes were associated with atmospheric forcing events.

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Variability in storm climate along the Gulf of Cadiz: the role of large scale atmospheric forcing and implications to coastal hazards

Climate Dynamics ◽

10.1007/s00382-015-2486-4 ◽

2015 ◽

Vol 45 (9-10) ◽

pp. 2499-2514 ◽

Cited By ~ 31

Author(s):

Theocharis A. Plomaritis ◽

Javier Benavente ◽

Irene Laiz ◽

Laura Del Río

Keyword(s):

Large Scale ◽

Coastal Hazards ◽

Atmospheric Forcing ◽

Gulf Of Cadiz ◽

Gulf Of Cádiz

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Imprint of chaotic ocean variability on transports in the Southwest Pacific at interannual timescales

10.5194/os-2020-102 ◽

2020 ◽

Author(s):

Sophie Cravatte ◽

Guillaume Serazin ◽

Thierry Penduff ◽

Christophe Menkes

Keyword(s):

Interannual Variability ◽

General Circulation ◽

Large Scale ◽

Southern Oscillation ◽

Initial Perturbation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Atmospheric Forcing ◽

Southwest Pacific ◽

Ocean Variability

Abstract. The Southwest Pacific Ocean sits at a bifurcation where southern subtropical waters are redistributed equatorward and poleward by different ocean currents. The processes governing the interannual variability of these currents are not completely understood. This issue is investigated using a probabilistic modeling strategy that allows disentangling the atmospherically-forced deterministic ocean variability and the chaotic intrinsic ocean variability. A large ensemble of 50 simulations performed with the same ocean general circulation model (OGCM) driven by the same realistic atmospheric forcing that only differ by a small initial perturbation is analyzed over 1980–2015. Our results show that, in the Southwest Pacific, the interannual variability of the transports is strongly dominated by chaotic ocean variability south of 20° S. In the tropics, while the interannual variability of transports and eddy kinetic energy modulation is largely deterministic and explained by El Nino Southern Oscillation (ENSO), ocean nonlinear processes still explain 10 to 20 % of their interannual variance at large-scale. Regions of strong chaotic variance generally coincide with regions of high mesoscale activity, suggesting that a spontaneous inverse cascade is at work from mesoscale toward lower frequencies and larger scales. The spatiotemporal features of the low-frequency oceanic chaotic variability are complex but spatially coherent within certain regions. In the Subtropical Countercurrent area, they appear as interannually-varying, zonally elongated alternating current structures, while in the EAC region, they are eddy-shaped. Given this strong imprint of large-scale chaotic oceanic fluctuations, our results question the attribution of interannual variability to the atmospheric forcing in the region from point-wise observations and one-member simulations.

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Imprint of chaotic ocean variability on transports in the southwestern Pacific at interannual timescales

Ocean Science ◽

10.5194/os-17-487-2021 ◽

2021 ◽

Vol 17 (2) ◽

pp. 487-507

Author(s):

Sophie Cravatte ◽

Guillaume Serazin ◽

Thierry Penduff ◽

Christophe Menkes

Keyword(s):

Interannual Variability ◽

General Circulation ◽

Large Scale ◽

Southern Oscillation ◽

Initial Perturbation ◽

Low Frequency ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Atmospheric Forcing ◽

Ocean Variability

Abstract. The southwestern Pacific Ocean sits at a bifurcation where southern subtropical waters are redistributed equatorward and poleward by different ocean currents. The processes governing the interannual variability of these currents are not completely understood. This issue is investigated using a probabilistic modeling strategy that allows disentangling the atmospherically forced deterministic ocean variability and the chaotic intrinsic ocean variability. A large ensemble of 50 simulations performed with the same ocean general circulation model (OGCM) driven by the same realistic atmospheric forcing and only differing by a small initial perturbation is analyzed over 1980–2015. Our results show that, in the southwestern Pacific, the interannual variability of the transports is strongly dominated by chaotic ocean variability south of 20∘ S. In the tropics, while the interannual variability of transports and eddy kinetic energy modulation are largely deterministic and explained by the El Niño–Southern Oscillation (ENSO), ocean nonlinear processes still explain 10 % to 20 % of their interannual variance at large scale. Regions of strong chaotic variance generally coincide with regions of high mesoscale activity, suggesting that a spontaneous inverse cascade is at work from the mesoscale toward lower frequencies and larger scales. The spatiotemporal features of the low-frequency oceanic chaotic variability are complex but spatially coherent within certain regions. In the Subtropical Countercurrent area, they appear as interannually varying, zonally elongated alternating current structures, while in the EAC (East Australian Current) region, they are eddy-shaped. Given this strong imprint of large-scale chaotic oceanic fluctuations, our results question the attribution of interannual variability to the atmospheric forcing in the region from pointwise observations and one-member simulations.

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