scholarly journals Laboratory simulations of the atmospheric mixed-layer in flow over complex topography

2017 ◽  
Vol 29 (2) ◽  
pp. 020702 ◽  
Author(s):  
Steven G. Perry ◽  
William H. Snyder
Keyword(s):  
Mixed Layer ◽  
Complex Topography ◽  
Laboratory Simulations ◽  
Atmospheric Mixed Layer

scholarly journals A Moist Quasi-Geostrophic Coupled Model: MQ-GCM2.0

2021 ◽  
Author(s):  
Sergey Kravtsov ◽  
Ilijana Mastilovic ◽  
Andrew McC. Hogg ◽  
William Dewar ◽  
Jeffrey Blundell
Keyword(s):  
Mixed Layer ◽  
Decadal Variability ◽  
Coupled Model ◽  
Realistic Model ◽  
Model Parameters ◽  
Wind Component ◽  
Apparent Lack ◽  
Ocean Atmosphere ◽  
Atmospheric Mixed Layer ◽  
New Formulation

Abstract. This paper contains a description of recent changes to the formulation and numerical implementation of the Quasi-Geostrophic Coupled Model (Q-GCM), which constitute a major update of the previous version of the model (Hogg et al., 2014). The Q-GCM model has been designed to provide an efficient numerical tool to study the dynamics of multi-scale mid-latitude air–sea interactions and their climatic impacts. The present additions/alterations were motivated by an inquiry into the dynamics of mesoscale ocean–atmosphere coupling and, in particular, by an apparent lack of Q-GCM atmosphere’s sensitivity to mesoscale sea-surface temperature (SST) anomalies, even at high (mesoscale) atmospheric resolutions, contrary to ample theoretical and observational evidence otherwise. Major modifications aimed at alleviating this problem include an improved radiative-convective scheme resulting in a more realistic model mean state and associated model parameters, a new formulation of entrainment in the atmosphere, which prompts more efficient communication between the atmospheric mixed layer and free troposphere, as well as an addition of temperature-dependent wind component in the atmospheric mixed layer and the resulting mesoscale feedbacks. The most drastic change is, however, the inclusion of moist dynamics in the model, which may be key to midlatitude ocean–atmosphere coupling. Accordingly, this version of the model is to be referred to as the MQ-GCM model. Overall, the MQ-GCM model is shown to exhibit a rich spectrum of behaviours reminiscent of many of the observed properties of the Earth’s climate system. It remains to be seen whether the added processes are able to affect in fundamental ways the simulated dynamics of the mid-latitude ocean–atmosphere system’s coupled decadal variability.

Turbulent length-scales in the marine atmospheric mixed layer

2010 ◽  
Vol 126 (566) ◽  
pp. 1889-1912 ◽  
Author(s):  
P. Durand ◽  
F. Thoumieux ◽  
D. Lambert
Keyword(s):  
Mixed Layer ◽  
Length Scales ◽  
Atmospheric Mixed Layer

scholarly journals An observational study of the evolution of the atmospheric boundary-layer over Cabo Frio, Brazil

2007 ◽  
Vol 25 (8) ◽  
pp. 1735-1744 ◽  
Author(s):  
S. H. Franchito ◽  
V. Brahmananda Rao ◽  
T. O. Oda ◽  
J. C. Conforte
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Mixed Layer ◽  
Coastal Upwelling ◽  
Vertical Mixing ◽  
Austral Summer ◽  
Sea Breeze ◽  
Austral Winter ◽  
Atmospheric Mixed Layer ◽  
Cabo Frio

Abstract. The effect of coastal upwelling on the evolution of the atmospheric boundary layer (ABL) in Cabo Frio (Brazil) is investigated. For this purpose, radiosounding data collected in two experiments made during the austral summer (upwelling case) and austral winter (no upwelling case) are analysed. The results show that during the austral summer, cold waters that crop up near the Cabo Frio coast favour the formation of an atmospheric stable layer, which persists during the upwelling episode. Due to the low SSTs, the descending branch of the sea-breeze circulation is located close to the coast, inhibiting the development of a mixed layer mainly during the day. At night, with the reduction of the land-sea thermal contrast the descending motion is weaker, allowing a vertical mixing. The stable ABL favours the formation of a low level jet, which may also contribute to the development of a nocturnal atmospheric mixed layer. During the austral winter, due to the higher SSTs observed near the coast, the ABL is less stable compared with that in the austral summer. Due to warming, a mixed layer is observed during the day. The observed vertical profiles of the zonal winds show that the easterlies at low levels are stronger in the austral summer, indicating that the upwelling modulates the sea-breeze signal, thus confirming model simulations.

scholarly journals Atmospheric Mixed Layer Convergence from Observed MJO Sea Surface Temperature Anomalies

2020 ◽  
Vol 33 (2) ◽  
pp. 547-558
Author(s):  
Simon P. de Szoeke ◽  
Eric D. Maloney
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Deep Convection ◽  
Equatorial Indian Ocean ◽  
Sea Surface ◽  
Planetary Rotation ◽  
Atmospheric Mixed Layer ◽  
Strong Winds ◽  
The Right

ABSTRACTThe Madden–Julian oscillation (MJO) dominates tropical weather on intraseasonal 30–90-day time scales, yet mechanisms for its generation, maintenance, and propagation remain unclear. Although surface moist static energy (MSE) flux is greatest under strong winds in the convective phase, sea surface temperature (SST) warms by ~0.3°C in the clear nonconvective phase of the MJO. Winds converging into the hydrostatic low pressure under warm air over the warm SST increase the vertically integrated MSE. We estimate column-integrated MSE convergence using a model of mixed layer (ML) winds balancing friction, planetary rotation, and hydrostatic pressure gradients. Small (0.3 K) SST anomalies associated with the MJO drive 7 W m−2 net column MSE convergence averaged over the equatorial Indian Ocean ahead of MJO deep convection. The MSE convergence is in the right phase to contribute to MJO generation and propagation. It is on the order of the total MSE tendency previously assessed from reanalysis, and greater than surface heat flux anomalies driven by intraseasonal SST fluctuations.

scholarly journals Observational description of the atmospheric and oceanic boundary layers over the Atlantic Ocean

2001 ◽  
Vol 49 (1-2) ◽  
pp. 49-59 ◽  
Author(s):  
Marcelo Dourado ◽  
Amauri Pereira de Oliveira
Keyword(s):  
Atlantic Ocean ◽  
Boundary Layers ◽  
Mixed Layer ◽  
Cold Front ◽  
Specific Humidity ◽  
Short Time Scale ◽  
Oceanic Mixed Layer ◽  
Vertical Extent ◽  
Atmospheric Mixed Layer ◽  
Cabo Frio

Time evolution of atmospheric and oceanic boundary layers are described for an upwelling region in the Atlantic Ocean located in Cabo Frio, Brazil (23°00'S, 42°08'W). The observations were obtained during a field campaign carried out by the "Instituto de Estudos do Mar Almirante Paulo Moreira", on board of the oceanographic ship Antares of the Brazilian Navy, between July 7 and 10 of 1992. The analysis shown here was based on 19 simultaneous vertical soundings of atmosphere and ocean, carried out consecutively every 4 hours. The period of observation was characterized by a passage of a cold front that penetrated in Cabo Frio on July 6. During the cold front passage the vertical extension of atmospheric (and oceanic) mixed layer varied from 200 m (and 13 m) to 1000 m (and 59 m). These changes occurred in the first day of observation and were followed by an increase of 1.2°C in the oceanic mixed layer temperature and by a decrease of 6 K and 6 g/kg in the virtual potential temperature and specific humidity of the atmospheric mixed layer. The short time scale variations in the ocean can be explained in terms of the substitution of cold upwelling water by warm downwelling water regime, as the surface winds shift from pre-frontal NE to post-frontal SSW during the cold front passage in Cabo Frio. The large vertical extent of the atmospheric mixed layer can be explained in terms of an intensification of the thermal mixing induced by the warming of the oceanic upper layers combined with the cooling of the lower atmospheric layers during the cold front passage. An intensification of the mechanical mixing, observed during the cold front passage, may also be contributing to the observed variations in the vertical extent of both layers.

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