scholarly journals Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations

2013 ◽  
Vol 118 (10) ◽  
pp. 4945-4964 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han ◽  
Toshiaki Shinoda ◽  
Chunzai Wang ◽  
Ren-Chieh Lien ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Solar Radiation ◽  
Mixed Layer ◽  
Diurnal Cycle ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer

Interannual variability of the Tropical Indian Ocean mixed layer depth

2012 ◽  
Vol 40 (3-4) ◽  
pp. 743-759 ◽  
Author(s):  
M. G. Keerthi ◽  
M. Lengaigne ◽  
J. Vialard ◽  
C. de Boyer Montégut ◽  
P. M. Muraleedharan
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer ◽  
Layer Depth ◽  
Ocean Mixed Layer Depth

scholarly journals A multilevel ocean mixed layer model resolving the diurnal cycle: Development and validation

2015 ◽  
Vol 7 (4) ◽  
pp. 1680-1692 ◽  
Author(s):  
Tiejun Ling ◽  
Min Xu ◽  
Xin-Zhong Liang ◽  
Julian X. L. Wang ◽  
Yign Noh
Keyword(s):  
Mixed Layer ◽  
Diurnal Cycle ◽  
Ocean Mixed Layer ◽  
Layer Model ◽  
Development And Validation ◽  
Mixed Layer Model

scholarly journals Modeling Diurnal and Intraseasonal Variability of the Ocean Mixed Layer

2005 ◽  
Vol 18 (8) ◽  
pp. 1190-1202 ◽  
Author(s):  
D. J. Bernie ◽  
S. J. Woolnough ◽  
J. M. Slingo ◽  
E. Guilyardi
Keyword(s):  
Mixed Layer ◽  
Diurnal Cycle ◽  
Intraseasonal Variability ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Ocean Mixed Layer ◽  
Tropical Ocean ◽  
Toga Coare ◽  
The Impact ◽  
The Western Pacific

Abstract The intraseasonal variability of SST associated with the passage of the Madden–Julian oscillation (MJO) is well documented; yet coupled model integrations generally underpredict the magnitude of this SST variability. Observations from the Improved Meteorological Instrument (IMET) mooring in the western Pacific during the intensive observing period (IOP) of the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) showed a large diurnal signal in SST that is modulated by the passage of the MJO. In this study, observations from the IOP of the TOGA COARE and a one-dimensional (1D) ocean mixed layer model incorporating the K-Profile Parameterization (KPP) vertical mixing scheme have been used to investigate the rectification of the intraseasonal variability of SST by the diurnal cycle and the implied impact of the absence of a representation of this process on the modeled intraseasonal variability in coupled GCMs. Analysis of the SST observations has shown that the increase of the daily mean SST by the diurnal cycle of SST accounts for about one-third of the magnitude of intraseasonal variability of SST associated with the Madden–Julian oscillation in the western Pacific warm pool. Experiments from the 1D model forced with fluxes at a range of temporal resolutions and with differing vertical resolution of the model have shown that to capture 90% of the diurnal variability of SST, and hence 95% of the intraseasonal variability of SST, requires a 3-h or better temporal resolution of the fluxes and a vertical grid with an upper-layer thickness of the order of 1 m. In addition to the impact of the representation of the diurnal cycle on the intraseasonal variability of SST, the strength of the mixing across the thermocline was found to be enhanced by the proper representation of the nighttime deep mixing in the ocean, implying a possible impact of the diurnal cycle onto the mean climate of the tropical ocean.

scholarly journals Impact of the Diurnal Cycle of Solar Radiation on Intraseasonal SST Variability in the Western Equatorial Pacific

2005 ◽  
Vol 18 (14) ◽  
pp. 2628-2636 ◽  
Author(s):  
Toshiaki Shinoda
Keyword(s):  
Solar Radiation ◽  
Mixed Layer ◽  
Diurnal Cycle ◽  
Intraseasonal Oscillation ◽  
Warm Pool ◽  
Surface Fluxes ◽  
Surface Cooling ◽  
Mixing Processes ◽  
Surface Warming ◽  
Sst Variability

Abstract The mechanism by which the diurnal cycle of solar radiation modulates intraseasonal SST variability in the western Pacific warm pool is investigated using a one-dimensional mixed layer model. SSTs in the model experiments forced with hourly surface fluxes during the calm–sunny phase of intraseasonal oscillation are significantly warmer than those with daily mean surface fluxes. The difference in two experiments is explained by upper-ocean mixing processes during nighttime. Surface warming during daytime creates a shallow diurnal warm layer near the surface (0–3 m), which can be easily eroded by surface cooling during nighttime. Further cooling, however, requires a substantial amount of energy because deeper waters need to be entrained into the mixed layer. Since the shallow diurnal layer is not formed in the experiment with daily mean surface fluxes, the SST for the hourly forcing case is warmer most of the time due to the diurnally varying solar radiation. Sensitivity of the intraseasonal SST variation to the penetrative component of solar radiation is examined, showing that the diurnal cycle plays an important role in the sensitivity. Solar radiation absorbed in the upper few meters significantly influences intraseasonal SST variations through changes in amplitude of diurnal SST variation.

scholarly journals Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer

2011 ◽  
Vol 8 (1) ◽  
pp. 247-289 ◽  
Author(s):  
A. Sirevaag ◽  
S. de la Rosa ◽  
I. Fer ◽  
M. Nicolaus ◽  
M. Tjernström ◽  
...  
Keyword(s):  
Heat Flux ◽  
Solar Radiation ◽  
Arctic Ocean ◽  
Mixed Layer ◽  
Heat Content ◽  
The Arctic ◽  
Upper Ocean ◽  
Ocean Mixed Layer ◽  
The Arctic Ocean ◽  
Melting Season

Abstract. A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the Central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance of solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22% of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the pycnocline accounted for the accumulated heat in the upper cold halocline during the melting season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m−2) and heated by solar radiation through the ice (−2.6 W m−2). An abrupt change in surface conditions halfway into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiation was reduced by 59% in the latter period. From hydrographic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.

scholarly journals Effect of Preconditioning on the Extreme Climate Events in the Tropical Indian Ocean*

2005 ◽  
Vol 18 (17) ◽  
pp. 3450-3469 ◽  
Author(s):  
H. Annamalai ◽  
J. Potemra ◽  
R. Murtugudde ◽  
J. P. McCreary
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Decadal Variability ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Ocean Model ◽  
Central Pacific ◽  
Atmospheric Teleconnection ◽  
The Mean ◽  
The 1960S

Abstract Sea surface temperature observations in the eastern equatorial Indian Ocean (EEIO) during the period 1950–2003 indicate that Indian Ocean dipole/zonal mode (IODZM) events are strong in two decades, namely, the 1960s and 1990s. Atmospheric reanalysis products in conjunction with output from an ocean model are examined to investigate the possible reason for the occurrence of strong IODZM events in these two decades. Specifically, the hypothesis that the mean thermocline in the EEIO is raised or lowered depending on the phase of Pacific decadal variability (PDV), preconditioning the EEIO to favor stronger or weaker IODZM activity, is examined. Diagnostics reveal that the EEIO is preconditioned by the traditional PDV signal (SVD1 of SST), deepening or shoaling the thermocline off south Java through its influence on the Indonesian Throughflow (ITF; oceanic teleconnection), and by residual decadal variability in the western and central Pacific (SVD2 of SST) that changes the equatorial winds over the Indian Ocean (atmospheric teleconnection). Both effects produce a background state that is either favorable or unfavorable for the thermocline–mixed layer interactions, and hence for the excitation of strong IODZM events. Collectively, SVD1 and SVD2 are referred to as PDV here. This hypothesis is tested with a suite of ocean model experiments. First, two runs are carried out, forced by climatological winds to which idealized easterly or westerly winds are added only over the equatorial Indian Ocean. As might be expected, in the easterly (westerly) run a shallower (deeper) thermocline is obtained over the EEIO. Then, observed winds from individual years are used to force the model. In these runs, anomalously cool SST in the EEIO develops only during decades when the thermocline is anomalously shallow, allowing entrainment of colder waters into the mixed layer. Since 1999 the PDV phase has changed, and consistent with this hypothesis the depth of the mean thermocline in the EEIO has been increasing. As a consequence, no IODZM developed during the El Niño of 2002, and only a weak cooling event occurred during the summer of 2003. This hypothesis likely also explains why some strong IODZM events occur in the absence of ENSO forcing, provided that PDV has preconditioned the EEIO thermocline to be anomalously shallow.

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