scholarly journals Some comments on "Importance of vertical mixing and barrier layer variation on seasonal mixed layer heat balance in the Bay of Bengal"

2017 ◽  
Author(s):  
Yun Qiu
Keyword(s):  
Mixed Layer ◽  
Barrier Layer ◽  
Bay Of Bengal ◽  
Heat Balance ◽  
Vertical Mixing

scholarly journals Importance of vertical mixing and barrier layer variation on seasonal mixed layer heat balance in the Bay of Bengal

2017 ◽  
Author(s):  
Ullala Pathiranage Gayan Pathirana ◽  
Gengxin Chen ◽  
Tilak Priyadarshana ◽  
Dongxiao Wang
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Barrier Layer ◽  
Bay Of Bengal ◽  
Heat Balance ◽  
Seasonal Cycle ◽  
Sensible Heat Flux ◽  
Vertical Mixing ◽  
Shortwave Radiation ◽  
Barrier Layer Thickness

Abstract. Time series measurements from the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings at 15° N, 90° E; 12° N, 90° E; 8° N, 90° E; 4° N, 90° E; 1.5° N, 90° E; 0° N, 90° E are used to investigate the seasonal mixed-layer heat balance and the importance of barrier layer thickness (BLT) and vertical mixing (Q−h) in the Bay of Bengal (BoB). It is found that the BLT, Q−h and mixed-layer heat balance all have a strong seasonality in the central BoB. Sea surface temperature (SST), salinity and wind are important for the observed strongest seasonal cycle of BLT in the central BoB, and wind is more important than the SST in the southern BoB. The heat storage rate (HSR) is primarily driven by latent heat flux and shortwave radiation (QSW and QL). Seasonal variations and the magnitudes of longwave radiation (QLW), sensible heat flux (QS), and horizontal mixed-layer heat advection are much weaker compared to those of QSW and QL. Q−h follows a pronounced seasonal cycle in the central BoB and is significantly positively correlated with the seasonal cycle of BLT at each mooring location. The seasonal variability of the stability favors the Q−h during winter and summer monsoon and suppress Q−h during monsoon transition periods. We found that Q−h plays the secondary role in the seasonal mixed-layer heat balance in the BoB. It is evident from the analysis that Q−h associated with temperature inversion (∆T) warms the mixed layer during winter and cools the mixed layer during summer. The warming tendency during winter is strong in the central BoB and weakens towards the equator, indicating a cooling tendency around the year. Our analysis further indicates the weakening of Q−h during monsoon transition periods favors the existence of warmer SST in the BoB, associated with thermal and salinity stratification in the central BoB.

scholarly journals Modulation of June Rainfall in India by Winter Salinity Barrier Layer in the Bay of Bengal

2020 ◽  
Author(s):  
Shanshan Pang ◽  
Xidong Wang ◽  
Gregory Foltz ◽  
Kaigui Fan
Keyword(s):  
Mixed Layer ◽  
Barrier Layer ◽  
Bay Of Bengal ◽  
Rainfall Variability ◽  
Sea Surface ◽  
Subsurface Water ◽  
Cmip5 Models ◽  
Tropospheric Temperature ◽  
Surface Cooling ◽  
Coupled Models

Abstract This study finds that the winter barrier layer (BL) in the Bay of Bengal (BoB) can modulate the subsequent Indian summer monsoon (ISM) onset and associated rainfall variability. In the years when the prior winter BL is anomalously thick, there is anomalous sea surface cooling caused by intensified latent heat flux loss, and this anomalous cooling persists into the following year due to positive cloud–SST feedback. During December–February, it is shown that the vertical entrainment of warmer subsurface water due to anomalously thick BL acts to limit excessive cooling of the sea surface and maintain deep atmospheric convection over the BoB. Then, during March–May, the thinner mixed layer linked to anomalously thick BL allows more shortwave radiation to penetrate below the mixed layer. This tends to reinforce the cold SST anomalies, and advance the onset of ISM and enhance June ISM precipitation through an increase in the tropospheric temperature gradient between land and sea. We also find that most CMIP5 models fail to reproduce the observed relationship between June ISM rainfall and the prior winter BL. This may be attributable to their difficulties in realistically simulating the winter BL in the BoB and ISM precipitation. The present results indicate that it is important to realistically capture the winter BL of the BoB in air–sea coupled models for improving the simulation and prediction of ISM.

scholarly journals Decreasing Biological Production and Carbon Export Due to the Barrier Layer: A Case Study in the Bay of Bengal

2021 ◽  
Vol 8 ◽  
Author(s):  
Huangchen Zhang ◽  
Linbin Zhou ◽  
Kaizhi Li ◽  
Zhixin Ke ◽  
Yehui Tan
Keyword(s):  
Barrier Layer ◽  
Bay Of Bengal ◽  
Coastal Waters ◽  
Physical Phenomenon ◽  
Vertical Mixing ◽  
Carbon Export ◽  
Biological Production ◽  
One Dimensional ◽  
Lower Carbon

A freshwater-induced barrier layer (BL) is a common physical phenomenon both in coastal waters and the open ocean. To examine the effects of BL on the biological production and the associated carbon export, a physical-biogeochemical survey was conducted in the Bay of Bengal. Severe depletions of surface phosphorus and the deepening of the nutricline were observed at the BL-affected stations due to the vertical mixing prohibition. The lowered surface chlorophyll a (Chl a) and squeezed deep Chl a maximum (DCM) layer also resulted in the ~18% lowered vertically integrated Chl a at the said stations. The composition of the net-sampled zooplankton was altered, and the abundance decreased by half at the BL-affected station (29.68 ind. m−3) compared with the unaffected station (55.52 ind. m−3). Such reductions in major zooplankton groups were confirmed by a video plankton recorder (VPR). The VPR observation indicated that there was a lower (by one-half) abundance of detritus at the BL-affected station, while the much lower carbon export flux rates were estimated to be at the BL-affected station (0.31 mg C m−2 d−1) rather than the unaffected station (0.77 mg C m−2 d−1). An idealized one-dimensional nutrient-phytoplankton-detritus model identified that the existence of BL can lead to decreased surface nutrients and phytoplankton concentrations, squeezed DCM layers, and lower detritus abundances. Finally, this study indicated that BL layers inhibit biological production and reduce carbon export, thus playing an important role in the ocean biogeochemical cycles.

scholarly journals On the Nature of Near-Inertial Oscillations in the Uppermost Part of the Ocean and a Possible Route toward HF Radar Probing of Stratification

2015 ◽  
Vol 45 (10) ◽  
pp. 2660-2678 ◽  
Author(s):  
Victor I. Shrira ◽  
Philippe Forget
Keyword(s):  
Mixed Layer ◽  
Vertical Mixing ◽  
Hf Radar ◽  
Momentum Exchange ◽  
Inertial Oscillations ◽  
Weak Density ◽  
Gulf Of Lion ◽  
Vertical Heat ◽  
Northwestern Mediterranean ◽  
Vertical Localization

AbstractInertial band response of the upper ocean to changing wind is studied both theoretically and by analysis of observations in the northwestern Mediterranean. On the nontraditional f plane, because of the horizontal component of the earth’s rotation for waves of inertial band with frequencies slightly below the local inertial frequency f, there is a waveguide in the mixed layer confined from below by the pycnocline. It is argued that when the stratification is shallow these waves are most easily and strongly excited by varying winds as near-inertial oscillations (NIOs). These motions have been overlooked in previous studies because they are absent under the traditional approximation. The observations that employed buoys with thermistors, ADCPs, and two 16.3-MHz Wellen Radar (WERA) HF radars were carried out in the Gulf of Lion in April–June 2006. The observations support the theoretical picture: a pronounced inertial band response occurs only in the presence of shallow stratification and is confined to the mixed layer, and the NIO penetration below the stratified layer is weak. NIO surface magnitude and vertical localization are strongly affected by the presence of even weak density stratification in the upper 10 m. The NIO surface signatures are easily captured by HF radars. Continuous 1.8-yr HF observations near the Porquerolles Island confirm that shallow stratification is indeed the precondition for a strong NIO response. The response sensitivity to stratification provides a foundation for developing HF radar probing of stratification and, indirectly, vertical mixing, including spotting dramatic mixing events and spikes of vertical heat, mass, and momentum exchange.

Variability of Upper Ocean Heat Balance in the Shikoku Basin during the Ocean Mixed Layer Experiment (OMLET)

2003 ◽  
Vol 59 (5) ◽  
pp. 619-627 ◽  
Author(s):  
Hirotaka Otobe ◽  
Keisuke Taira ◽  
Shoji Kitagawa ◽  
Tomio Asai ◽  
Kimio Hanawa
Keyword(s):  
Mixed Layer ◽  
Heat Balance ◽  
Upper Ocean ◽  
Ocean Mixed Layer ◽  
Shikoku Basin

scholarly journals In situ vertical profiles of aerosol extinction, mass, and composition over the southeast United States during SENEX and SEAC<sup>4</sup>RS: observations of a modest aerosol enhancement aloft

2015 ◽  
Vol 15 (12) ◽  
pp. 7085-7102 ◽  
Author(s):  
N. L. Wagner ◽  
C. A. Brock ◽  
W. M. Angevine ◽  
A. Beyersdorf ◽  
P. Campuzano-Jost ◽  
...  
Keyword(s):  
United States ◽  
Mixed Layer ◽  
Transition Layer ◽  
Southeastern United States ◽  
Vertical Mixing ◽  
Organic Aerosol ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Secondary Aerosol

Abstract. Vertical profiles of submicron aerosol from in situ aircraft-based measurements were used to construct aggregate profiles of chemical, microphysical, and optical properties. These vertical profiles were collected over the southeastern United States (SEUS) during the summer of 2013 as part of two separate field studies: the Southeast Nexus (SENEX) study and the Study of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS). Shallow cumulus convection was observed during many profiles. These conditions enhance vertical transport of trace gases and aerosol and create a cloudy transition layer on top of the sub-cloud mixed layer. The trace gas and aerosol concentrations in the transition layer were modeled as a mixture with contributions from the mixed layer below and the free troposphere above. The amount of vertical mixing, or entrainment of air from the free troposphere, was quantified using the observed mixing ratio of carbon monoxide (CO). Although the median aerosol mass, extinction, and volume decreased with altitude in the transition layer, they were ~10 % larger than expected from vertical mixing alone. This enhancement was likely due to secondary aerosol formation in the transition layer. Although the transition layer enhancements of the particulate sulfate and organic aerosol (OA) were both similar in magnitude, only the enhancement of sulfate was statistically significant. The column integrated extinction, or aerosol optical depth (AOD), was calculated for each individual profile, and the transition layer enhancement of extinction typically contributed less than 10 % to the total AOD. Our measurements and analysis were motivated by two recent studies that have hypothesized an enhanced layer of secondary aerosol aloft to explain the summertime enhancement of AOD (2–3 times greater than winter) over the southeastern United States. The first study attributes the layer aloft to secondary organic aerosol (SOA) while the second study speculates that the layer aloft could be SOA or secondary particulate sulfate. In contrast to these hypotheses, the modest enhancement we observed in the transition layer was not dominated by OA and was not a large fraction of the summertime AOD.

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