Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

2006 ◽  
Vol 123 (2) ◽  
pp. 219-237 ◽  
Author(s):  
Eric D. Skyllingstad ◽  
Dean Vickers ◽  
Larry Mahrt ◽  
Roger Samelson
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Atmospheric Boundary Layer ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
Marine Atmospheric Boundary Layer

scholarly journals The surface thermal signature and air–sea coupling over the Agulhas rings propagating in the South Atlantic Ocean interior

Ocean Science ◽  
2014 ◽  
Vol 10 (4) ◽  
pp. 633-644 ◽  
Author(s):  
J. M. A. C. Souza ◽  
B. Chapron ◽  
E. Autret
Keyword(s):  
Boundary Layer ◽  
Atlantic Ocean ◽  
Surface Temperature ◽  
Atmospheric Boundary Layer ◽  
Sea Surface Temperature ◽  
Surface Wind ◽  
Sea Surface ◽  
Ekman Pumping ◽  
Marine Atmospheric Boundary Layer ◽  
Sst Anomalies

Abstract. The surface signature of Agulhas rings propagating across the South Atlantic Ocean is observed based on three independent data sets: Advanced Microwave Scanning Radiometer for the Earth Observing System/Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) (TMI/AMSR-E) satellite sea surface temperature, Argo profiling floats and a merged winds product derived from scatterometer observations and reanalysis results. A persistent pattern of cold (negative) sea surface temperature (SST) anomalies in the eddy core, with warm (positive) anomalies at the boundary, is revealed. This pattern contrasts with the classical idea of a warm core anticyclone. Taking advantage of a moving reference frame corresponding to the altimetry-detected Agulhas rings, modifications of the surface winds by the ocean-induced currents and SST gradients are evaluated using satellite SST and wind observations. As obtained, the averaged stationary thermal expression and mean eddy-induced circulation are coupled to the marine atmospheric boundary layer, leading to surface wind anomalies. Consequently, an average Ekman pumping associated with these mean surface wind variations consistently emerges. This average Ekman pumping is found to explain very well the SST anomaly signatures of the detected Agulhas rings. Particularly, this mechanism seems to be the key factor determining that these anticyclonic eddies exhibit stationary imprints of cold SST anomalies near their core centers. A residual phase with the maximum sea surface height (SSH) anomaly and wind speed anomaly is found to the right of the mean wind direction, apparently maintaining a coherent stationary thermal expression coupled to the marine atmospheric boundary layer.

scholarly journals Relação entre o Vapor D’Água Atmosférico e a Temperatura da Superfície do Mar Sobre a Região da Confluência Brasil-Malvinas, com Base em Dados Coletados In Situ (Relationship between Atmospheric Water Vapor Content and the Sea Surface Temperature in the Brazil-Malvinas Confluence considering Data Collected In Situ)

2019 ◽  
Vol 12 (5) ◽  
pp. 1687
Author(s):  
Rose Ane Pereira De Freitas ◽  
Ronald Buss Souza ◽  
Rafael Reis ◽  
Douglas Lindemann
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Surface Temperature ◽  
Atmospheric Boundary Layer ◽  
Sea Surface Temperature ◽  
Water Vapor Content ◽  
Sea Surface ◽  
Specific Humidity ◽  
Vapor Concentration

A atmosfera consiste em um dos menores reservatórios de água do planeta, contribuindo com 0,001% da massa total da água presente, porém, sendo de fundamental importância para os processos físicos na atmosfera. A partir de dados obtidos através de 130 perfis de radiossondas realizados durante dez cruzeiros oceanográficos nos meses de outubro e novembro, entre 2004 e 2015, analisa-se a influência dos gradientes de temperatura da superfície do mar (TSM) e a passagem de sistemas atmosféricos transientes na variabilidade espaço-temporal da concentração de vapor d’água da camada limite atmosférica marinha (CLAM), sobre a região da Confluência Brasil Malvinas (CBM), enfatizando-se a Operação Antártica 31 (OP31). Os dados de vapor d’água são obtidos calculando-se umidade específica em superfície e água precipitável dentro da camada limite atmosférica. Os resultados mostram que os gradientes térmicos entre as águas quentes da Corrente do Brasil (CB) e as águas frias da Corrente das Malvinas (CM) produzem diferenças significativas no conteúdo de vapor d'água da CLAM nos dois lados da frente oceanográfica. Na superfície, o valor médio da umidade específica sobre o lado quente (frio) foi 8,4 ± 1,67 mm (7,08 ± 1,51 mm). A CLAM foi localmente modulada pela TSM, sendo cerca de 2g/kg mais úmida sobre a região quente da frente oceanográfica em relação à região fria. Em todas as observações realizadas, o vapor d’água integrado na CLAM foi diretamente influenciada pela passagem de sistemas atmosféricos transiente.    A B S T R A C TThe atmosphere is the smallest contributor of the planet's water tanks, providing only 0.001% of the water total mass, however, it is of fundamental importance for playing a key role in the atmosphere's physical processes. The data were obtained from 130 radiosondes profiles taken during ten oceanographic cruises carried out during the months of October and November between 2004 and 2015, analyzed the influence of the sea surface temperature (SST) gradients and the passage of transient atmospheric systems at the spatial-temporal variability of the water vapor concentration within the marine atmospheric boundary layer (MABL), over Brazil-Malvinas Confluence (BMC), emphasizing the Antarctic Operation 31 (AO31). Water vapor data are obtained by calculating surface specific moisture and precipitable water within the atmospheric boundary layer. The results show that the thermal gradients between the warm waters of Brazil Current and the cold waters of the Malvinas Current were able to produce significant differences in the water vapor content of the MABL on both sides of the oceanographic front. On the surface, the average of the specific humidity over the warm (cold) side was 8.4 ± 1.67 mm (7.08 ± 1.51 mm). The MABL was locally modulated by the SST, being about 2 g/kg wetter over the warm part of the front with respect to the cold one. In all the observations made, the water vapor integrated in the MABL was directly influenced by the passage of transient atmospheric systems.Key words: Southwest Atlantic; Oceanographic front; Transient atmospheric system

scholarly journals The Atmospheric Response to Weak Sea Surface Temperature Fronts*

2015 ◽  
Vol 72 (9) ◽  
pp. 3356-3377 ◽  
Author(s):  
Niklas Schneider ◽  
Bo Qiu
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Atmospheric Boundary Layer ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Large Scale ◽  
Sea Surface ◽  
Coupling Coefficients ◽  
Wind Stress Curl ◽  
Sst Gradient

Abstract The response of the atmospheric boundary layer to fronts of sea surface temperature (SST) is characterized by correlations between wind stress divergence and the downwind component of the SST gradient and between the wind stress curl and the crosswind component of the SST gradient. The associated regression (or coupling) coefficients for the wind stress divergence are consistently larger than those for the wind stress curl. To explore the underlying physics, the authors introduce a linearized model of the atmospheric boundary layer response to SST-induced modulations of boundary layer hydrostatic pressure and vertical mixing in the presence of advection by a background Ekman spiral. Model solutions are a strong function of the SST scale and background advection and recover observed characteristics. The coupling coefficients for wind stress divergence and curl are governed by distinct physics. Wind stress divergence results from either large-scale winds crossing the front or from a thermally direct, cross-frontal circulation. Wind stress curl, expected to be largest when winds are parallel to SST fronts, is reduced through geostrophic spindown and thereby yields weaker coupling coefficients.

Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature Perturbations

2014 ◽  
Vol 142 (11) ◽  
pp. 4284-4307 ◽  
Author(s):  
Natalie Perlin ◽  
Simon P. de Szoeke ◽  
Dudley B. Chelton ◽  
Roger M. Samelson ◽  
Eric D. Skyllingstad ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Coupling Coefficient ◽  
Eddy Viscosity ◽  
Sea Surface ◽  
Coupling Coefficients ◽  
Wind Response ◽  
Speed Response

Abstract The wind speed response to mesoscale SST variability is investigated over the Agulhas Return Current region of the Southern Ocean using the Weather Research and Forecasting (WRF) Model and the U.S. Navy Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model. The SST-induced wind response is assessed from eight simulations with different subgrid-scale vertical mixing parameterizations, validated using Quick Scatterometer (QuikSCAT) winds and satellite-based sea surface temperature (SST) observations on 0.25° grids. The satellite data produce a coupling coefficient of sU = 0.42 m s−1 °C−1 for wind to mesoscale SST perturbations. The eight model configurations produce coupling coefficients varying from 0.31 to 0.56 m s−1 °C−1. Most closely matching QuikSCAT are a WRF simulation with the Grenier–Bretherton–McCaa (GBM) boundary layer mixing scheme (sU = 0.40 m s−1 °C−1), and a COAMPS simulation with a form of Mellor–Yamada parameterization (sU = 0.38 m s−1 °C−1). Model rankings based on coupling coefficients for wind stress, or for curl and divergence of vector winds and wind stress, are similar to that based on sU. In all simulations, the atmospheric potential temperature response to local SST variations decreases gradually with height throughout the boundary layer (0–1.5 km). In contrast, the wind speed response to local SST perturbations decreases rapidly with height to near zero at 150–300 m. The simulated wind speed coupling coefficient is found to correlate well with the height-averaged turbulent eddy viscosity coefficient. The details of the vertical structure of the eddy viscosity depend on both the absolute magnitude of local SST perturbations, and the orientation of the surface wind to the SST gradient.

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