scholarly journals Interannual Variability in the North Atlantic Ocean’s Temperature Field and Its Association with the Wind Stress Forcing

2017 ◽  
Vol 30 (7) ◽  
pp. 2655-2678 ◽  
Author(s):  
Andreas Groth ◽  
Yizhak Feliks ◽  
Dmitri Kondrashov ◽  
Michael Ghil
Keyword(s):  
Temperature Field ◽  
Interannual Variability ◽  
Wind Stress ◽  
North Atlantic ◽  
Gulf Stream ◽  
Singular Spectrum Analysis ◽  
Sea Surface ◽  
Atmospheric Forcing ◽  
The North ◽  
The North Atlantic

Spectral analyses of the North Atlantic temperature field in the Simple Ocean Data Analysis (SODA) reanalysis identify prominent and statistically significant interannual oscillations along the Gulf Stream front and in large regions of the North Atlantic. A 7–8-yr oscillatory mode is characterized by a basinwide southwest-to-northeast–oriented propagation pattern in the sea surface temperature (SST) field. This pattern is found to be linked to a seesaw in the meridional dipole structure of the zonal wind stress forcing (TAUX). In the subpolar gyre, the SST and TAUX fields of this mode are shown to be in phase opposition, which suggests a cooling effect of the wind stress on the upper ocean layer. Over all, this mode’s temperature field is characterized by a strong equivalent-barotropic component, as shown by covariations in SSTs and sea surface heights, and by phase-coherent behavior of temperature layers at depth with the SST field. Recent improvements of multivariate singular spectrum analysis (M-SSA) help separate spatiotemporal patterns. This methodology is developed further and applied to studying the ocean’s response to variability in the atmospheric forcing. Statistical evidence is shown to exist for other mechanisms generating oceanic variability of similar 7–8-yr periodicity in the Gulf Stream region; the latter variability is likewise characterized by a strongly equivalent-barotropic component. Two other modes of biennial variability in the Gulf Stream region are also identified, and it is shown that interannual variability in this region cannot be explained by the ocean’s response to similar variability in the atmospheric forcing alone.

scholarly journals Interannual Variability of High-Wind Occurrence over the North Atlantic*

2011 ◽  
Vol 24 (24) ◽  
pp. 6515-6527 ◽  
Author(s):  
Xuhua Cheng ◽  
Shang-Ping Xie ◽  
Hiroki Tokinaga ◽  
Yan Du
Keyword(s):  
Interannual Variability ◽  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Surface Air Temperature ◽  
High Wind ◽  
The North ◽  
The North Atlantic ◽  
The Difference ◽  
The North Atlantic Oscillation

Abstract Interannual variability of high-wind occurrence over the North Atlantic is investigated based on observations from the satellite-borne Special Sensor Microwave Imager (SSM/I). Despite no wind direction being included, SSM/I data capture major features of high-wind frequency (HWF) quite well. Climatology maps show that HWF is highest in winter and is close to zero in summer. Remarkable interannual variability of HWF is found in the vicinity of the Gulf Stream, over open sea south of Iceland, and off Cape Farewell, Greenland. On interannual scales, HWF south of Iceland has a significant positive correlation with the North Atlantic Oscillation (NAO). An increase in the mean westerlies and storm-track intensity during a positive NAO event cause HWF to increase in this region. In the vicinity of the Gulf Stream, HWF is significantly correlated with the difference between sea surface temperature and surface air temperature (SST − SAT), indicative of the importance of atmospheric instability. Cross-frontal wind and an SST gradient are important for the instability of the marine atmospheric boundary layer on the warm flank of the SST front. Off Cape Farewell, high wind occurs in both westerly and easterly tip jets. Quick Scatterometer (QuikSCAT) data show that variability in westerly (easterly) HWF off Cape Farewell is positively (negatively) correlated with the NAO.

Remote impact of North Atlantic sea surface temperature errors in sub‐seasonal forecasts

2021 ◽  
Author(s):  
Chris Roberts ◽  
Frederic Vitart ◽  
Magdalena Balmaseda
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Positive Impact ◽  
Ocean Waves ◽  
Sea Surface ◽  
Time Range ◽  
Seasonal Forecasts ◽  
Geophysical Research ◽  
The North ◽  
The North Atlantic

<p>The ECMWF sub-seasonal forecast model includes dynamic representations of the atmosphere, ocean, sea-ice, and ocean-waves. Coupling to a dynamic ocean model allows more a realistic representation of air-sea interaction, but also introduces the potential for systematic errors in sea surface temperatures (SST). Here, we show that North Atlantic SST biases associated with errors in the position of the Gulf Stream have a significant impact on initialized forecasts at the sub‐seasonal time range. Correcting these errors with an online SST bias‐correction scheme improves the mean state of the North Atlantic region and has a significant positive impact on forecasts of atmospheric circulation anomalies. Improvements to forecast skill extend beyond the North Atlantic into Europe and along the northern hemisphere subtropical waveguide. These impacts provide important evidence for the potential benefits to initialized coupled forecast systems of higher‐resolution ocean models that can better resolve the position of the Gulf Stream.</p><p>Reference: Roberts, C. D., Vitart, F., & Balmaseda, M. A. Hemispheric impact of North Atlantic SSTs in sub‐seasonal forecasts. Geophysical Research Letters, e2020GL091446.</p>

scholarly journals Interannual Variability in North Atlantic Weather: Data Analysis and a Quasigeostrophic Model

2016 ◽  
Vol 73 (8) ◽  
pp. 3227-3248 ◽  
Author(s):  
Yizhak Feliks ◽  
Andrew W. Robertson ◽  
Michael Ghil
Keyword(s):  
Interannual Variability ◽  
North Atlantic ◽  
Gulf Stream ◽  
Weather Data ◽  
Jet Stream ◽  
Intrinsic Variability ◽  
Storm Activity ◽  
Sst Front ◽  
The North ◽  
The North Atlantic

Abstract This paper addresses the effect of interannual variability in jet stream orientation on weather systems over the North Atlantic basin (NAB). The observational analysis relies on 65 yr of NCEP–NCAR reanalysis (1948–2012). The total daily kinetic energy of the geostrophic wind (GTKE) is taken as a measure of storm activity over the North Atlantic. The NAB is partitioned into four rectangular regions, and the winter average of GTKE is calculated for each quadrant. The spatial GTKE average over all four quadrants shows striking year-to-year variability and is strongly correlated with the North Atlantic Oscillation (NAO). The GTKE strength in the northeast quadrant is closely related to the diffluence angle of the jet stream in the northwest quadrant. To gain insight into the relationship between the diffluence angle and its downstream impact, a quasigeostrophic baroclinic model is used. The results show that an initially zonal jet persists at its initial latitude over 30 days or longer, while a tilted jet propagates meridionally according to the Rossby wave group velocity, unless kept stationary by external forcing. A Gulf Stream–like narrow sea surface temperature (SST) front provides the requisite forcing for an analytical steady-state solution to this problem. This SST front influences the atmospheric jet in the northwest quadrant: it both strengthens the jet and tilts it northward at higher levels, while its effect is opposite at lower levels. Reanalysis data confirm these effects, which are consistent with thermal wind balance. The results suggest that the interannual variability found in the GTKE may be caused by intrinsic variability of the thermal Gulf Stream front.

scholarly journals The Combined Effects of SST and the North Atlantic Subtropical High-Pressure System on the Atlantic Basin Tropical Cyclone Interannual Variability

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 329
Author(s):  
Albenis Pérez-Alarcón ◽  
José C. Fernández-Alvarez ◽  
Rogert Sorí ◽  
Raquel Nieto ◽  
Luis Gimeno
Keyword(s):  
High Pressure ◽  
Interannual Variability ◽  
Central America ◽  
North Atlantic ◽  
The West ◽  
The Bahamas ◽  
Pressure System ◽  
North Atlantic Subtropical High ◽  
The North ◽  
The North Atlantic

The combined effect of the sea surface temperature (SST) and the North Atlantic subtropical high-pressure system (NASH) in the interannual variability of the genesis of tropical cyclones (TCs) and landfalling in the period 1980–2019 is explored in this study. The SST was extracted from the Centennial Time Scale dataset from the National Oceanic and Atmospheric Administration (NOAA), and TC records were obtained from the Atlantic Hurricane Database of the NOAA/National Hurricane Center. The genesis and landfalling regions were objectively clustered for this analysis. Seven regions of TC genesis and five for landfalling were identified. Intercluster differences were observed in the monthly frequency distribution and annual variability, both for genesis and landfalling. From the generalized least square multiple regression model, SST and NASH (intensity and position) covariates can explain 22.7% of the variance of the frequency of TC genesis, but it is only statistically significant (p < 0.1) for the NASH center latitude. The SST mostly modulates the frequency of TCs formed near the West African coast, and the NASH latitudinal variation affects those originated in the Lesser Antilles arc. For landfalling, both covariates explain 38.7% of the variance; however, significant differences are observed in the comparison between each region. With a statistical significance higher than 90%, SST and NASH explain 33.4% of the landfalling variability in the archipelago of the Bahamas and central–eastern region of Cuba. Besides, landfalls in the Gulf of Mexico and Central America seem to be modulated by SST. It was also found there was no statistically significant relationship between the frequency of genesis and landfalling with the NASH intensity. However, the NASH structure modulates the probability density of the TCs trajectory that make landfall once or several times in their lifetime. Thus, the NASH variability throughout a hurricane season affects the TCs trajectory in the North Atlantic basin. Moreover, we found that the landfalling frequency of TCs formed near the West Africa coast and the central North Atlantic is relatively low. Furthermore, the SST and NASH longitude center explains 31.6% (p < 0.05) of the variance of the landfalling intensity in the archipelago of the Bahamas, while the SST explains 26.4% (p < 0.05) in Central America. Furthermore, the 5-year moving average filter revealed decadal and multidecadal variability in both genesis and landfalling by region. Our findings confirm the complexity of the atmospheric processes involved in the TC genesis and landfalling.

scholarly journals Space-Time Sea Surface pCO2 Estimation in the North Atlantic Based on CatBoost

2021 ◽  
Vol 13 (14) ◽  
pp. 2805
Author(s):  
Hongwei Sun ◽  
Junyu He ◽  
Yihui Chen ◽  
Boyu Zhao
Keyword(s):  
North Atlantic ◽  
Function Analysis ◽  
Biological Activities ◽  
Mixed Layer Depth ◽  
Sea Surface ◽  
Coefficient Of Determination ◽  
Mean Bias Error ◽  
Bias Error ◽  
The North ◽  
The North Atlantic

Sea surface partial pressure of CO2 (pCO2) is a critical parameter in the quantification of air–sea CO2 flux, which plays an important role in calculating the global carbon budget and ocean acidification. In this study, we used chlorophyll-a concentration (Chla), sea surface temperature (SST), dissolved and particulate detrital matter absorption coefficient (Adg), the diffuse attenuation coefficient of downwelling irradiance at 490 nm (Kd) and mixed layer depth (MLD) as input data for retrieving the sea surface pCO2 in the North Atlantic based on a remote sensing empirical approach with the Categorical Boosting (CatBoost) algorithm. The results showed that the root mean square error (RMSE) is 8.25 μatm, the mean bias error (MAE) is 4.92 μatm and the coefficient of determination (R2) can reach 0.946 in the validation set. Subsequently, the proposed algorithm was applied to the sea surface pCO2 in the North Atlantic Ocean during 2003–2020. It can be found that the North Atlantic sea surface pCO2 has a clear trend with latitude variations and have strong seasonal changes. Furthermore, through variance analysis and EOF (empirical orthogonal function) analysis, the sea surface pCO2 in this area is mainly affected by sea temperature and salinity, while it can also be influenced by biological activities in some sub-regions.

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