scholarly journals Feasible Method for the Assimilation of Satellite-Derived SST with an Ocean Circulation Model

2005 ◽  
Vol 22 (6) ◽  
pp. 746-756 ◽  
Author(s):  
Atsuyoshi Manda ◽  
Naoki Hirose ◽  
Tetsuo Yanagi
Keyword(s):  
Ocean Circulation ◽  
Mixed Layer ◽  
Thermal Structure ◽  
Circulation Model ◽  
Strong Nonlinearity ◽  
Layer Model ◽  
Ocean Circulation Model ◽  
One Dimensional ◽  
Nudging Method ◽  
Mixed Layer Model

Abstract The surface restoring condition of satellite-derived sea surface temperatures (SSTs) is validated as a feasible assimilation method with an ocean circulation model that incorporates the strongly nonlinear mixed layer model. The restoring treatment is an empirical method for correcting the heat flux in order to pull the predicted SST toward the observed SST; it is referred to as the nudging method in this study. A one-dimensional experiment is conducted to evaluate the skill of the nudging method. The mixed layer model (MLM) used in the experiment is a second-order turbulence closure model that has a strong nonlinearity. The skill of the nudging method is compared with that of an ensemble Kalman filter, which is a statistically optimal method for nonlinear dynamic models. Although the nudging method is statistically suboptimal, the result of the experiment shows that the skill of this method is comparable when using an appropriate restoring time scale. A three-dimensional experiment using an ocean general circulation model (OGCM), which incorporates the same MLM as that used in the one-dimensional experiment, is also conducted to further examine the skill of the nudging method. By applying the nudging method to the OGCM, the model improves the estimated thermal structure not only near the surface, but also in the subsurface layers.

A one-dimensional mixed-layer model for stratified shelf seas with tide- and wind-induced mixing

1984 ◽  
Vol 37 (1) ◽  
pp. 3-27 ◽  
Author(s):  
Hendrik Mattheus van Aken
Keyword(s):  
Mixed Layer ◽  
Layer Model ◽  
One Dimensional ◽  
Shelf Seas ◽  
Mixed Layer Model

scholarly journals Parameterization of Langmuir Circulation in the Ocean Mixed Layer Model Using LES and Its Application to the OGCM

2016 ◽  
Vol 46 (1) ◽  
pp. 57-78 ◽  
Author(s):  
Yign Noh ◽  
Hyejin Ok ◽  
Eunjeong Lee ◽  
Takahiro Toyoda ◽  
Naoki Hirose
Keyword(s):  
Mixed Layer ◽  
High Latitude ◽  
General Circulation ◽  
Circulation Model ◽  
Langmuir Circulation ◽  
Ocean Mixed Layer ◽  
Layer Model ◽  
Tropical Ocean ◽  
Common Error ◽  
Mixed Layer Model

AbstractThe effect of Langmuir circulation (LC) on vertical mixing is parameterized in the ocean mixed layer model (OMLM), based on the analysis of large-eddy simulation (LES) results. Parameterization of LC effects is carried out in terms of the modifications of the mixing length scale as well as the inclusion of the contribution from the Stokes force in momentum and TKE equations. The performance of the new OMLM is examined by comparing with LES results, together with sensitivity tests for empirical constants used in the parameterization. The new OMLM is then applied to the ocean general circulation model (OGCM) Meteorological Research Institute Community Ocean Model (MRI.COM), and its effect is investigated. The new OMLM helps to correct too shallow mixed layer depths (MLDs) in the high-latitude ocean, which has been a common error in most OGCMs, without making the thermocline in the tropical ocean more diffused. The parameterization of LC effects is found to affect mainly the high-latitude ocean, in which the MLD is shallow in summer and stratification is weak in winter.

scholarly journals Convection and heat transfer in island (warm) wakes

2020 ◽  
Author(s):  
Cátia C. Azevedo ◽  
Carolina M. L. Camargo ◽  
José Alves ◽  
Rui M. A. Caldeira
Keyword(s):  
Ocean Circulation ◽  
Mixed Layer ◽  
Density Ratio ◽  
Circulation Model ◽  
Sea Surface ◽  
North Coast ◽  
Leeward Side ◽  
Vertical Profiles ◽  
Ocean Circulation Model ◽  
Convection And Heat Transfer

AbstractThe interaction between the incoming winds with high mountainous islands produces a wind-sheltered area in the leeward side, known as the atmospheric wake. In addition to weaker winds, the wake is also characterized by a clearing of clouds, resulting in intense solar radiation reaching the sea surface. As a consequence, a warm oceanic wake forms on the leeward side. This phenomenon detectable from space can extend 100 km offshore of Madeira, where the sea surface temperature can be 4⁰C higher than the surrounding oceanic waters. This study considers in-situ, remote sensing, and ocean circulation model data, to investigate the effects of the warm wake in the vertical structure of the upper ocean. To characterize the convective layer (25-70m) developing within the oceanic wake, 200 vertical profiles of temperature, salinity and turbulence were considered, together with the computation of the Density Ratio and Turner-angle. In comparison to the open-ocean water column, wake waters are strongly stratified with respect to temperature although highly unstable. The vertical profiles of salinity show distinct water parcels that sink and/or rise as a response to the intense heat fluxes. During the night, the ocean surface cools, leading to the stretching of the mixed layer which was replicated by the ocean circulation model. In exposed, non-wake regions however, particularly in the southeast and north coast of the island, the stretching of the mixed layer is not detectable.

scholarly journals Attribution of Forced Decadal Climate Change in Coupled and Uncoupled Ocean–Atmosphere Model Experiments

2017 ◽  
Vol 30 (16) ◽  
pp. 6203-6223 ◽  
Author(s):  
Buwen Dong ◽  
Rowan T. Sutton ◽  
Len Shaffrey ◽  
Nicholas P. Klingaman
Keyword(s):  
Mixed Layer ◽  
General Circulation ◽  
Climate Model ◽  
Coupled Model ◽  
Surface Air Temperature ◽  
Circulation Model ◽  
Layer Model ◽  
Local Circulation ◽  
Model Experiments ◽  
Mixed Layer Model

There is still no consensus about the best methodology for attributing observed changes in climate or climate events. One widely used approach relies on experiments in which the time periods of interest are simulated using an atmospheric general circulation model (AGCM) forced by prescribed sea surface temperatures (SSTs), with and without estimated anthropogenic influences. A potential limitation of such experiments is the lack of explicit atmosphere–ocean coupling; therefore a key question is whether the attribution statements derived from such studies are in fact robust. In this research the authors have carried out climate model experiments to test attribution conclusions in a situation where the answer is known—a so-called perfect model approach. The study involves comparing attribution conclusions for decadal changes derived from experiments with a coupled climate model (specifically an AGCM coupled to an ocean mixed-layer model) with conclusions derived from parallel experiments with the same AGCM forced by SSTs derived from the coupled model simulations. Results indicate that attribution conclusions for surface air temperature changes derived from AGCM experiments are generally robust and not sensitive to air–sea coupling. However, changes in seasonal mean and extreme precipitations, and circulation in some regions, show large sensitivity to air–sea coupling, notably in the summer monsoons over East Asia and Australia. Comparison with observed changes indicates that the coupled simulations generally agree better with observations. These results demonstrate that the AGCM-based attribution method has limitations and may lead to erroneous attribution conclusions in some regions for local circulation and mean and extreme precipitation. The coupled mixed-layer model used in this study offers an alternative and, in some respects, superior tool for attribution studies.

Seasonal mixed-layer dynamics in an eddy-resolving ocean circulation model

2013 ◽  
Vol 118 (7) ◽  
pp. 3387-3405 ◽  
Author(s):  
Andreas Schiller ◽  
Ken R. Ridgway
Keyword(s):  
Ocean Circulation ◽  
Mixed Layer ◽  
Circulation Model ◽  
Ocean Circulation Model
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