scholarly journals Turbulent Mixing Inferred from CTD Datasets in the Western Tropical Pacific Ocean

2020 ◽  
Vol 25 (4) ◽  
pp. 148-156
Author(s):  
Adi Purwandana ◽  
Mochamad Riza Iskandar
Keyword(s):  
Pacific Ocean ◽  
Dissipation Rate ◽  
Direct Method ◽  
World Ocean ◽  
Tropical Pacific ◽  
Water Masses ◽  
Tropical Pacific Ocean ◽  
Mesoscale Circulations ◽  
Western Tropical Pacific ◽  
Dissipation Rates

The spatial pattern of energetic aspect related to vertical mixing processes of the water masses in the western tropical Pacific Ocean is characterized in this study. Turbulent kinetic energy dissipation rates and vertical eddy diffusivities in this region are estimated from archived CTD profiles from World Ocean Database (WOD). The dissipation rates are estimated using the improved Thorpe method which considered the canonical Garret-Munk background dissipation rate and the typical lowest value dissipation rate from microstructure measurements, 10-10 m2s-3. Enhanced dissipation rates of 10-8-10-7 m2s-3 were found in the region known as an active area where two Pacific water masses from different sources intersect and strong mesoscale circulations exist while lower dissipation of less than 10-8 m2s-3 was found in the less active regions. A comparison with recent 3D hydrostatic model of M2 internal tide shows less agreement dissipation rates of the model with the observations, with the decreasing trend of discrepancy towards deeper. This suggested that topography roughness, homogenous stratifications yet lacking of background circulations set in the model were not sufficient to reproduce dissipation in the region with strong background mesoscale circulations. It was indicated that the main contributor for vertical overturning events occurred in this region is due to strong shear instabilities enhanced by background circulations. A direct method estimates using vertical microstructure profiler is suggested to validate this indirect method in the future.

Intraseasonal Variability of the Surface Zonal Currents in the Western Tropical Pacific Ocean: Characteristics and Mechanisms

2016 ◽  
Vol 46 (12) ◽  
pp. 3639-3660 ◽  
Author(s):  
Fan Wang ◽  
Yuanlong Li ◽  
Jianing Wang
Keyword(s):  
Pacific Ocean ◽  
Ocean Circulation ◽  
General Circulation ◽  
Intraseasonal Variability ◽  
Circulation Model ◽  
Tropical Pacific ◽  
North Equatorial Current ◽  
Tropical Pacific Ocean ◽  
Western Tropical Pacific ◽  
Equatorial Current

AbstractThe surface circulation of the tropical Pacific Ocean is characterized by alternating zonal currents, such as the North Equatorial Current (NEC), North Equatorial Countercurrent (NECC), South Equatorial Current (SEC), and South Equatorial Countercurrent (SECC). In situ measurements of subsurface moorings and satellite observations reveal pronounced intraseasonal variability (ISV; 20–90 days) of these zonal currents in the western tropical Pacific Ocean (WTPO). The amplitude of ISV is the largest within the equatorial band exceeding 20 cm s−1 and decreases to ~10 cm s−1 in the NECC band and further to 4–8 cm s−1 in the NEC and SECC. The ISV power generally increases from high frequencies to low frequencies and exhibits a peak at 50–60 days in the NECC, SEC, and SECC. These variations are faithfully reproduced by an ocean general circulation model (OGCM) forced by satellite winds, and parallel model experiments are performed to gain insights into the underlying mechanisms. It is found that large-scale ISV (>500 km) is primarily caused by atmospheric intraseasonal oscillations (ISOs), such as the Madden–Julian oscillation (MJO), through wind stress forcing. These signals are confined within 10°S–8°N, mainly as baroclinic ocean wave responses to ISO winds. For scales shorter than 200 km, ISV is dominated by ocean internal variabilities with mesoscale structures. They arise from the baroclinic and barotropic instabilities associated with the vertical and horizontal shears of the upper-ocean circulation. The ISV exhibits evident seasonal variation, with larger (smaller) amplitude in boreal winter (summer) in the SEC and SECC.

Review on observational studies of western tropical Pacific Ocean circulation and climate

2020 ◽  
Vol 38 (4) ◽  
pp. 906-929 ◽  
Author(s):  
Dunxin Hu ◽  
Fan Wang ◽  
Janet Sprintall ◽  
Lixin Wu ◽  
Stephen Riser ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Ocean Circulation ◽  
Observational Studies ◽  
Tropical Pacific ◽  
Tropical Pacific Ocean ◽  
Western Tropical Pacific

scholarly journals Impact of East Asian Winter and Australian Summer Monsoons on the Enhanced Surface Westerlies over the Western Tropical Pacific Ocean Preceding the El Niño Onset

2014 ◽  
Vol 27 (5) ◽  
pp. 1928-1944 ◽  
Author(s):  
Yangxing Zheng ◽  
Renhe Zhang ◽  
Mark A. Bourassa
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
East Asian ◽  
Atmospheric Model ◽  
Tropical Pacific ◽  
Tropical Pacific Ocean ◽  
Western Tropical Pacific ◽  
Enhanced Surface ◽  
Australian Summer

Abstract Composite analysis from NCEP–NCAR reanalysis datasets over the period 1948–2007 indicates that stronger East Asian winter monsoons (EAWM) and stronger Australian summer monsoons (ASM) generally coexist in boreal winters preceding the onset of El Niño, although the EAWM tend to be weak after 1990, probably because of the decadal shift of EAWM and the change in El Niño events from cold-tongue type to warm-pool type. The anomalous EAWM and ASM enhance surface westerlies over the western tropical Pacific Ocean (WTP). It is proposed that the enhanced surface westerlies over the WTP prior to El Niño onset are generally associated with the concurrent anomalous EAWM and ASM. A simple analytical atmospheric model is constructed to test the hypothesis that the emergence of enhanced surface westerlies over the WTP can be linked to concurrent EAWM and ASM anomalies. Model results indicate that, when anomalous northerlies from the EAWM converge with anomalous southerlies from the ASM, westerly anomalies over the WTP are enhanced. This result provides a possible explanation of the co-impact of the EAWM and the ASM on the onset of El Niño through enhancing the surface westerly over the WTP.

scholarly journals Semiannual variation in the western tropical Pacific Ocean

2008 ◽  
Vol 35 (16) ◽  
Author(s):  
Tangdong Qu ◽  
Jianping Gan ◽  
Akio Ishida ◽  
Yuji Kashino ◽  
Tomoki Tozuka
Keyword(s):  
Pacific Ocean ◽  
Tropical Pacific ◽  
Tropical Pacific Ocean ◽  
Western Tropical Pacific ◽  
Semiannual Variation
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