scholarly journals Topographic and Mixed Layer Submesoscale Currents in the Near-Surface Southwestern Tropical Pacific

2017 ◽  
Vol 47 (6) ◽  
pp. 1221-1242 ◽  
Author(s):  
Kaushik Srinivasan ◽  
James C. McWilliams ◽  
Lionel Renault ◽  
Hristina G. Hristova ◽  
Jeroen Molemaker ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Layer ◽  
Kinetic Energy ◽  
Wind Stress ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Seasonal Cycle ◽  
Surface Heat ◽  
Near Surface ◽  
Coral Sea

AbstractThe distribution and strength of submesoscale (SM) surface layer fronts and filaments generated through mixed layer baroclinic energy conversion and submesoscale coherent vortices (SCVs) generated by topographic drag are analyzed in numerical simulations of the near-surface southwestern Pacific, north of 16°S. In the Coral Sea a strong seasonal cycle in the surface heat flux leads to a winter SM “soup” consisting of baroclinic mixed layer eddies (MLEs), fronts, and filaments similar to those seen in other regions farther away from the equator. However, a strong wind stress seasonal cycle, largely in sync with the surface heat flux cycle, is also a source of SM processes. SM restratification fluxes show distinctive signatures corresponding to both surface cooling and wind stress. The winter peak in SM activity in the Coral Sea is not in phase with the summer dominance of the mesoscale eddy kinetic energy in the region, implying that local surface layer forcing effects are more important for SM generation than the nonlocal eddy deformation field. In the topographically complex Solomon and Bismarck Seas, a combination of equatorial proximity and boundary drag generates SCVs with large-vorticity Rossby numbers (Ro ~ 10). River outflows in the Bismarck and Solomon Seas make a contribution to SM generation, although they are considerably weaker than the topographic effects. Mean to eddy kinetic energy conversions implicate barotropic instability in SM topographic wakes, with the strongest values seen north of the Vitiaz Strait along the coast of Papua New Guinea.

The Annual Range of Southern Hemisphere SST: Comparison with Surface Heating and Possible Reasons for the High-Latitude Falloff*

2010 ◽  
Vol 23 (8) ◽  
pp. 1994-2009 ◽  
Author(s):  
A. M. Chiodi ◽  
D. E. Harrison
Keyword(s):  
Heat Flux ◽  
Southern Hemisphere ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Seasonal Cycle ◽  
Mixed Layer Depth ◽  
Surface Heat ◽  
Upper Ocean ◽  
Layer Depth ◽  
Annual Range

Abstract Globally, the seasonal cycle is the largest single component of observed sea surface temperature (SST) variability, yet it is still not fully understood. Herein, the degree to which the structure of the seasonal cycle of Southern Hemisphere SST can be explained by the present understanding of surface fluxes and upper-ocean physics is examined. It has long been known that the annual range of Southern Hemisphere SST is largest in the midlatitudes, despite the fact that the annual range of net surface heat flux peaks well poleward of the SST peak. The reasons for this discrepancy (“falloff of the annual range of SST”) are determined here through analysis of net surface heat flux estimates, observed SST, and mixed layer depth data, and results from experiments using two different one-dimensional ocean models. Results show that (i) the classical explanations for the structure of the annual range of SST in the Southern Hemisphere are incomplete, (ii) current estimates of surface heat flux and mixed layer depth can be used to accurately reproduce the observed annual range of SST, and (iii) the prognostic mixed layer models used here often fail to adequately reproduce the seasonal cycle at higher latitudes, despite performing remarkably well in other regions. This suggests that more work is necessary to understand the changes of upper-ocean dynamics that occur with latitude.

scholarly journals On the Effect of Surface Heat-Flux Heterogeneities on the Mixed-Layer-Top Entrainment

2014 ◽  
Vol 151 (3) ◽  
pp. 531-556 ◽  
Author(s):  
Matthias Sühring ◽  
Björn Maronga ◽  
Florian Herbort ◽  
Siegfried Raasch
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Effect Of Surface

scholarly journals Dryline Bulge Evolution in a Two-Dimensional Mixed-Layer Model

2004 ◽  
Vol 61 (21) ◽  
pp. 2528-2543 ◽  
Author(s):  
Glenn M. Auslander ◽  
Peter R. Bannon
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Mixed Layer Depth ◽  
Surface Heat ◽  
Two Dimensional ◽  
Layer Model ◽  
Layer Depth ◽  
Inversion Strength ◽  
Mixed Layer Model

Abstract This study examines the diurnal response of a mixed-layer model of the dryline system to localized anomalies of surface heat flux, topography, mixed-layer depth, and inversion strength. The two-dimensional, mixed-layer model is used to simulate the dynamics of a cool, moist layer east of the dryline capped by an inversion under synoptically quiescent conditions. The modeled domain simulates the sloping topography of the U.S. Great Plains. The importance of this study can be related to dryline bulges that are areas with enhanced convergence that may trigger convection in suitable environmental conditions. All anomalies are represented by a Gaussian function in the horizontal whose amplitude, size, and orientation can be altered. A positive, surface-heat-flux anomaly produces increased mixing that creates a bulge toward the east, while a negative anomaly produces a westward bulge. Anomalies in topography show a similar trend in bulge direction with a peak giving an eastward bulge, and a valley giving a westward bulge. Anomalies in the initial mixed-layer depth yield an eastward bulge in the presence of a minimum and a westward bulge for a maximum. An anomaly in the initial inversion strength results in a westward bulge when the inversion is stronger, and an eastward bulge when the inversion is weak. The bulges observed in this study at 1800 LT ranged from 400 to 600 km along the dryline and from 25 to 80 km across the dryline. When the heating ceases at night, the entrainment and eastward movement of the line stops, and the line surges westward. This westward surge at night has little dependence on the type of anomaly applied. Whether a westward or eastward bulge was present at 1800 LT, the surge travels an equal distance toward the west. However, the inclusion of weak nocturnal friction reduces the westward surge by 100 to 200 km due to mechanical mixing of the very shallow leading edge of the surge. All model runs exhibit peaks in the mixed-layer depth along the dryline at 1800 LT caused by enhanced boundary layer convergence and entrainment of elevated mixed-layer air into the mixed layer. These peaks appear along the section of the dryline that is least parallel to the southerly flow. They vary in amplitude from 4 to 9 km depending on the amplitude of the anomaly. However, the surface-heat-flux anomalies generally result in peaks at the higher end of this interval. It is hypothesized that the formation of these peaks may be the trigger for deep convection along the dryline in the late afternoon.

scholarly journals Seasonality of Decadal Sea Surface Temperature Anomalies in the Northwestern Pacific

2006 ◽  
Vol 19 (12) ◽  
pp. 2953-2968 ◽  
Author(s):  
Takashi Mochizuki ◽  
Hideji Kida
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Heat Budget ◽  
Surface Heat ◽  
Sea Surface ◽  
Northwestern Pacific ◽  
Sst Anomaly

Abstract The seasonality of the decadal sea surface temperature (SST) anomalies and the related physical processes in the northwestern Pacific were investigated using a three-dimensional bulk mixed layer model. In the Kuroshio–Oyashio Extension (KOE) region, the strongest decadal SST anomaly was observed during December–February, while that of the central North Pacific occurred during February–April. From an examination of the seasonal heat budget of the ocean mixed layer, it was revealed that the seasonal-scale enhancement of the decadal SST anomaly in the KOE region was controlled by horizontal Ekman temperature transport in early winter and by vertical entrainment in autumn. The temperature transport by the geostrophic current made only a slight contribution to the seasonal variation of the decadal SST anomaly, despite controlling the upper-ocean thermal conditions on decadal time scales through the slow Rossby wave adjustment to the wind stress curl. When averaging over the entire KOE region, the contribution from the net sea surface heat flux was also no longer significantly detected. By examining the horizontal distributions of the local thermal damping rate, however, it was concluded that the wintertime decadal SST anomaly in the eastern KOE region was rather damped by the net sea surface heat flux. It was due to the fact that the anomalous local thermal damping of the SST anomaly resulting from the vertical entrainment in autumn was considerably strong enough to suppress the anomalous local atmospheric thermal forcing that acted to enhance the decadal SST anomaly.

scholarly journals Estimating the effect of rainfall on the surface temperature of a tropical lake

2018 ◽  
Author(s):  
Gabriel Gerard Rooney ◽  
Nicole van Lipzig ◽  
Wim Thiery
Keyword(s):  
Heat Flux ◽  
Surface Layer ◽  
Kinetic Energy ◽  
Surface Temperature ◽  
Surface Air Temperature ◽  
Daily Rainfall ◽  
Tropical Lake ◽  
Lake Surface ◽  
Near Surface ◽  
Potential Control

Abstract. We make use of a unique high-quality, long-term observational dataset on a tropical lake to assess the effect of rainfall on lake surface temperature. The lake in question is Lake Kivu, one of the African Great Lakes, and was selected for its remarkably uniform climate and availability of multi-year, over-lake meteorological observations. Rain may have a cooling effect on the lake surface by lowering the near-surface air temperature, by the direct rain heat flux into the lake, by mixing the lake surface layer through the flux of kinetic energy, and by convective mixing of the lake surface layer. The potential importance of the rainfall effect is discussed in terms of both heat flux and kinetic-energy flux. To estimate the rainfall effect on the mean diurnal cycle of lake surface temperature, the data are binned into categories of daily rainfall amount. They are further filtered based on comparable values of daily mean net radiation, which reduces the influence of radiative-flux differences. Our results indicate that days with heavy rainfall may experience a reduction in lake surface temperature of approximately 0.3 K by the end of the day compared to days with light-to-moderate rainfall. Overall this study highlights a new potential control on lake surface temperature, and suggests that further efforts are needed to quantify this effect in other regions and to include this process in atmospheric models.

Frontolysis by surface heat flux in the eastern Japan Sea: importance of mixed layer depth

2019 ◽  
Vol 75 (3) ◽  
pp. 283-297 ◽  
Author(s):  
Shun Ohishi ◽  
Hidenori Aiki ◽  
Tomoki Tozuka ◽  
Meghan F. Cronin
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Mixed Layer Depth ◽  
Japan Sea ◽  
Surface Heat ◽  
Layer Depth ◽  
Eastern Japan
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