scholarly journals Understanding the 2017 warm event in North Tropical Atlantic

2020 ◽  
Author(s):  
Ana Trindade ◽  
Marta Matín-Rey ◽  
Marcos Portabella ◽  
Eleftheria Exarchou ◽  
Pablo Ortega ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Large Scale ◽  
Temporal Frequency ◽  
Surface Wind ◽  
Sea Surface ◽  
Earth Model ◽  
Tropical Atlantic ◽  
Ocean Wind ◽  
North Tropical Atlantic

<p>The Atlantic Ocean has suffered tremendous warming during recent decades as a consequence of anthropogenic forcing, modulated by the natural low frequency variability. Special attention should be paid to the high temporal frequency of warm interannual events in the North Tropical Atlantic (NTA) since the early 2000s, resulting in the most intense hurricane seasons on record (Hallam et al., 2017; Lim et al., 2018; Murakami et al., 2018; Klotzbach et al., 2018; Camp et al., 2018). Moreover, NTA sea surface temperature anomalies during boreal spring have been suggested as a potential precursor to the Equatorial Mode (Foltz and McPhaden, 2010ab; Burmeister et al., 2016; Martín-Rey and Lazar, 2019; Martín-Rey et al., 2019).<strong> </strong></p><p>This study aims to investigate the development of the 2017 NTA spring-summer warming event, which was the strongest of the last decade, as well as the importance of an accurate ocean forcingin the simulation of this event. For such purpose, a set of four simulations using distinct ocean wind forcing products, namely from the EC-Earth model, ERA-Interim (ERAi) reanalysis and a new ERAi-corrected ocean wind product (ERAstar), have been performed and analysed.The latter consists of average geolocated scatterometer-based corrections applied to ERAi output (Trindade et al., 2019).In this sense, ERAstar includes some of the physical processes missing or misrepresented by ERA-i, and corrects for large-scale NWP parameterization and dynamical errors.</p><p>The air-sea processes underlying the onset and development of the warm 2017 NTA event and the wave activity present in the equatorial Atlantic will be explored to determine their possible connection with the equatorial sea surface temperature variability. Furthermore, the comparison between the different experiments allows us to validate the new surface wind dataset and evaluate the importance of accurate, high-resolution ocean forcing in the representation of tropical Atlantic variability.</p>

Covariability of Surface Wind and Stress Responses to Sea Surface Temperature Fronts

2012 ◽  
Vol 25 (17) ◽  
pp. 5916-5942 ◽  
Author(s):  
Larry W. O’Neill ◽  
Dudley B. Chelton ◽  
Steven K. Esbensen
Keyword(s):  
Stress Response ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Stress Responses ◽  
Large Scale ◽  
Surface Wind ◽  
Nonlinear Function ◽  
Algebraic Manipulation ◽  
Sea Surface ◽  
Earth Observing System

Abstract The responses of surface wind and wind stress to spatial variations of sea surface temperature (SST) are investigated using satellite observations of the surface wind from the Quick Scatterometer (QuikSCAT) and SST from the Advanced Microwave Scanning Radiometer on the Advanced Microwave Scanning Radiometer for Earth Observing System (EOS) (AMSR-E) Aqua satellite. This analysis considers the 7-yr period June 2002–May 2009 during which both instruments were operating. Attention is focused in the Kuroshio, North and South Atlantic, and Agulhas Return Current regions. Since scatterometer wind stresses are computed solely as a nonlinear function of the scatterometer-derived 10-m equivalent neutral wind speed (ENW), qualitatively similar responses of the stress and ENW to SST are expected. However, the responses are found to be more complicated on the oceanic mesoscale. First, the stress and ENW are both approximately linearly related to SST, despite a nonlinear relationship between them. Second, the stress response to SST is 2 to 5 times stronger during winter compared to summer, while the ENW response to SST exhibits relatively little seasonal variability. Finally, the stress response to SST can be strong in regions where the ENW response is weak and vice versa. A straightforward algebraic manipulation shows that the stress perturbations are directly proportional to the ENW perturbations multiplied by a nonlinear function of the ambient large-scale ENW. This proportionality explains why both the stress and ENW depend linearly on the mesoscale SST perturbations, while the dependence of the stress perturbations on the ambient large-scale ENW explains both the seasonal pulsing and the geographic variability of the stress response to SST compared with the less variable ENW response.

Interannual sea surface chlorophyll-a signature in the tropical Atlantic

2021 ◽  
Author(s):  
Fanny Chenillat ◽  
Julien Jouanno ◽  
Serena Illig ◽  
Founi Mesmin Awo ◽  
Gaël Alory ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Cold Tongue ◽  
Equatorial Atlantic ◽  
Atlantic Region ◽  
The North ◽  
Sst Anomaly ◽  
Equatorial Band ◽  
North Tropical Atlantic

<div><span>Surface chlorophyll-<em>a </em>concentration (CHL-<em>a</em>) remotely observed by satellite shows a marked seasonal and interannual variability in the Tropical Atlantic, with potential consequences on the marine trophic web. Seasonal and interannual CHL-<em>a </em>variability peaks in boreal summer and shows maxima in the equatorial Atlantic region at 10˚W, spreading from 0 to 30˚W. In this study, we analyze how the remotely-sensed surface CHL-<em>a </em>responds to the leading climate modes affecting the interannual equatorial Atlantic variability over the 1998-2018 period, namely the Atlantic Zonal Mode (AZM) and the North Tropical Atlantic Mode (NTA, also known as the Atlantic Meridional Mode). The AZM is characterized by anomalous warming (or cooling) along the eastern equatorial band. In contrast, the NTA is characterized by an interhemispheric pattern of the sea surface temperature (SST), with anomalous warm (cold) conditions in the north tropical Atlantic region and weak negative (positive) SST anomalies south of the equator. We show that both modes significantly drive the interannual Tropical Atlantic surface CHL-<em>a </em>variability, with different timings and contrasted modulation on the eastern and western portions of the cold tongue area. Our results also reveal that the NTA slightly dominates (40%) the summer tropical Atlantic interannual variability over the last two decades, most probably because of a positive phase of the Atlantic multidecadal oscillation. For each mode of variability, we analyze an event characterized by an extreme negative sea surface temperature (SST) anomaly in the Atlantic equatorial band. Both modes are associated with a positive CHL-<em>a </em>anomaly at the equator. In 2002, a negative phase of the NTA led to cold SST anomaly and high positive CHL-<em>a </em>in the western portion of the cold tongue, peaking in June-July and lasting until the end of the year. In contrast, in 2005, a negative phase of the AZM drove cool temperature and positive CHL-<em>a </em>in the eastern equatorial band, with a peak in May-June and almost no signature after August. Such contrasted year to year conditions can affect the marine ecosystem by changing temporal and spatial trophic niches for pelagic predators, thus inducing significant variations for ecosystem functioning and fisheries.</span></div>

scholarly journals Sea surface wind perturbations over the Kashevarov Bank of the Okhotsk Sea: a satellite study

2011 ◽  
Vol 29 (2) ◽  
pp. 393-399
Author(s):  
T. I. Tarkhova ◽  
M. S. Permyakov ◽  
E. Yu. Potalova ◽  
V. I. Semykin
Keyword(s):  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Surface Wind ◽  
Sea Surface ◽  
Cold Spot ◽  
Okhotsk Sea ◽  
Autumn Period ◽  
Sea Surface Wind ◽  
Spot Center

Abstract. Sea surface wind perturbations over sea surface temperature (SST) cold anomalies over the Kashevarov Bank (KB) of the Okhotsk Sea are analyzed using satellite (AMSR-E and QuikSCAT) data during the summer-autumn period of 2006–2009. It is shown, that frequency of cases of wind speed decreasing over a cold spot in August–September reaches up to 67%. In the cold spot center SST cold anomalies reached 10.5 °C and wind speed lowered down to ~7 m s−1 relative its value on the periphery. The wind difference between a periphery and a centre of the cold spot is proportional to SST difference with the correlations 0.5 for daily satellite passes data, 0.66 for 3-day mean data and 0.9 for monthly ones. For all types of data the coefficient of proportionality consists of ~0.3 m s−1 on 1 °C.

Sign in / Sign up

Export Citation Format

Share Document