Determination of Absorption Lengths using PWP Model in the Bay of Bengal

2021 ◽  
Author(s):  
Hitesh Gupta ◽  
Sourav Sil
Keyword(s):  
Bay Of Bengal ◽  
Water Body ◽  
Turbulent Mixing ◽  
Heat Budget ◽  
Sea Surface ◽  
Absorption Length ◽  
Rama Buoy ◽  
1D Model ◽  
Mixed Layer Heat Budget ◽  
Length Changes

<p>In this study, we model the upper layers of the Bay of Bengal, which is rather a unique water body in terms of its dynamics which is controlled by the advection of large fresh water from the adjoining rivers as well monsoonal precipitation thus changing the turbulent mixing in the upper layers. The fresh water influx from rivers and precipitation, leads to low saline water overlying hypersaline water, creates a strong stratification due to which turbulent mixing is inhibited. The resulting halocline inhibits the wind driven mixing of the upper layers thus changing or affecting the optical characteristics of the water body. With the exception of shortwave insolation, the air – sea heat exchange occurs at the sea surface and is vertically redistributed by mixing and advection. The present study focuses on generating these optical or absorption lengths (e-folding depths) at different locations in the Bay of Bengal as a function of time itself, showing absorption length changes with both the space and the time, using the PWP – 1D model for which data is obtained from RAMA Buoys located along 90<sup>0</sup>E in the Bay of Bengal. The shortwave and longwave absorption length is directly related to heating up of the upper layers of the ocean and thus change its state and dynamics. Heating of the upper oceanic layers are also related to increase in SST as well as the Ocean Heat content of the ocean leading to changes in various systems like monsoon, cyclones, fluxes, etc. These absorption lengths are related to the Mixed layer heat budget directly but it may also be related to the salt budget of the Bay too. The model results highlight that the absorption length affects the SST as well as the temperature of the upper layers and also that the absorption length changes from one season to another season done using the data of - RAMA Buoy located at 90<sup>0</sup>E and 15<sup>0</sup>N (northern Bay of Bengal) and 90<sup>0</sup>E and 12<sup>0</sup>N as well as data from INCOIS tropflux. The study encourages to use the generated results for the Mixed layer heat budget analysis, or for the modelling purpose, etc.</p><p> </p><p><strong>Keywords - </strong>Bay of Bengal, Mixing in the upper layers, Absorption lengths, extinction lengths, Penetration depths, E-folding depth, RAMA buoy, Solar insolation, Water type and quality, Sea surface temperature, PWP – 1D model, Seasonality.</p>

Seasonal Cycle of the Mixed Layer Heat Budget in the Northeastern Tropical Atlantic Ocean

2013 ◽  
Vol 26 (20) ◽  
pp. 8169-8188 ◽  
Author(s):  
Gregory R. Foltz ◽  
Claudia Schmid ◽  
Rick Lumpkin
Keyword(s):  
Mixed Layer ◽  
Annual Cycle ◽  
Turbulent Mixing ◽  
Seasonal Cycle ◽  
Heat Budget ◽  
Heat Content ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Mixed Layer Heat Budget ◽  
Vertical Turbulent Mixing

Abstract The seasonal cycle of the mixed layer heat budget in the northeastern tropical Atlantic (0°–25°N, 18°–28°W) is quantified using in situ and satellite measurements together with atmospheric reanalysis products. This region is characterized by pronounced latitudinal movements of the intertropical convergence zone (ITCZ) and strong meridional variations of the terms in the heat budget. Three distinct regimes within the northeastern tropical Atlantic are identified. The trade wind region (15°–25°N) experiences a strong annual cycle of mixed layer heat content that is driven by approximately out-of-phase annual cycles of surface shortwave radiation (SWR), which peaks in boreal summer, and evaporative cooling, which reaches a minimum in boreal summer. The surface heat-flux-induced changes in the mixed layer heat content are damped by a strong annual cycle of cooling from vertical turbulent mixing, estimated from the residual in the heat balance. In the ITCZ core region (3°–8°N) a weak seasonal cycle of mixed layer heat content is driven by a semiannual cycle of SWR and damped by evaporative cooling and vertical turbulent mixing. On the equator the seasonal cycle of mixed layer heat content is balanced by an annual cycle of SWR that reaches a maximum in October and a semiannual cycle of turbulent mixing that cools the mixed layer most strongly during May–July and November. These results emphasize the importance of the surface heat flux and vertical turbulent mixing for the seasonal cycle of mixed layer heat content in the northeastern tropical Atlantic.

scholarly journals Oceanic Response to Tropical Cyclone Gonu (2007) in the Gulf of Oman and the Northern Arabian Sea: Estimating Depth of the Mixed Layer Using Satellite SST and Climatological Data

2021 ◽  
Vol 9 (11) ◽  
pp. 1244
Author(s):  
Kamran Koohestani ◽  
Mohammad Nabi Allahdadi ◽  
Nazanin Chaichitehrani
Keyword(s):  
Tropical Cyclone ◽  
Surface Temperature ◽  
Mixed Layer ◽  
Turbulent Mixing ◽  
Arabian Sea ◽  
Heat Budget ◽  
Sea Surface ◽  
Gulf Of Oman ◽  
Northern Arabian Sea ◽  
Budget Equation

The category 5-equivalent tropical Cyclone Gonu (2007) was the strongest cyclone to enter the northern Arabian Sea and Gulf of Oman. The impact of this cyclone on the sea surface temperature (SST) cooling and deepening of the mixed layer was investigated herein using an optimally interpolated (OI) cloud-free sea surface temperature (SST) dataset, climatological profiles of water temperature, and data from Argo profilers. SST data showed a maximum cooling of 1.7–6.5 °C during 1–7 June 2007 over the study area, which is similar to that of slow- to medium-moving cyclones in previous studies. The oceanic heat budget equation with the assumptions of the dominant turbulent mixing effect was used to establish relationships between SST and mixed layer depth (MLD) for regions that were directly affected by cyclone-induced turbulent mixing. The relationships were applied to the SST maps from satellite to obtain maps of MLD for 1–7 June, when Gonu was over the study area. Comparing with the measured MLD from Argo data showed that this approach estimated the MLDs with an average error of 15%, which is an acceptable amount considering the convenience of this approach in estimating MLD and the simplifications applied in the heat budget equation. Some inconsistencies in calculating MLD were attributed to use of climatological temperature profiles that may not have appropriately represented the pre-cyclone conditions due to pre-existing cold/warm core eddies. Estimation of the diapycnal diffusion that quantified the turbulent mixing across the water column showed consistent temporal and spatial variations with the calculated MLDs.

scholarly journals A Polar Low Pair over the Norwegian Sea

2009 ◽  
Vol 137 (8) ◽  
pp. 2559-2575 ◽  
Author(s):  
Burghard Brümmer ◽  
Gerd Müller ◽  
Gunnar Noer
Keyword(s):  
Heat Budget ◽  
Cloud Layer ◽  
Sea Surface ◽  
Cloud Base ◽  
Aircraft Measurements ◽  
Polar Lows ◽  
The North ◽  
Polar Low ◽  
Upper Level Jet ◽  
Almost All

Abstract During the Lofotes cyclone experiment (LOFZY 2005), two polar lows developed one behind the other inside a cold-air outbreak from the north in the lee of Spitsbergen on 7 March 2005. Buoys, ship, and aircraft measurements as well as satellite imagery are applied to analyze the polar low bulk properties, the horizontal and vertical structure, and the mass, moisture, and heat budget. The lifetime of the system until landfall at northern Norway was 12 h. The generation occurred under the left exit region of an upper-level jet with 70 m s−1. Both polar lows had a radius of 100–130 km and extended to a height of about 2.5 km. The propagation speeds were within 14–17 m s−1 and correspond to the vertically averaged wind velocity of the lowest 2.5 km. In the polar low centers the pressure was about 2–3 hPa lower and the air was 1–2 K warmer and drier than in the surroundings. Aircraft measurements in the second of the two polar lows show an embedded frontlike precipitation band north of the center. Here, the highest low-level winds with 25 m s−1 and the largest fluxes of sensible and latent heat with 290 and 520 W m−2, respectively, were measured (areal averages amounted to 115 and 190 W m−2). Aircraft data show mass convergence in the subcloud layer (0–900 m) and divergence in the cloud layer (900–2500 m). Moisture supply by evaporation from the sea surface was about twice as large as that by convergence in the subcloud layer. The condensation rate in the cloud layer nearly equaled the rate of evaporation at the sea surface. Almost all condensed cloud water was converted to precipitation water. Only half of the precipitation at the cloud base reached the sea surface.

Seasonal and Interannual Sea Surface Temperature Variability in the Coastal Cities of Arabian Sea and Bay of Bengal

2004 ◽  
Vol 31 (2) ◽  
pp. 549-560 ◽  
Author(s):  
Tariq Masood Ali Khan ◽  
Dewan Abdul Quadir ◽  
Tad S. Murty ◽  
Majajul Alam Sarker
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Temperature Variability ◽  
Sea Surface ◽  
Coastal Cities

scholarly journals Interannual Variability of Sea Surface Temperature off Java and Sumatra in a Global GCM*

2008 ◽  
Vol 21 (11) ◽  
pp. 2451-2465 ◽  
Author(s):  
Yan Du ◽  
Tangdong Qu ◽  
Gary Meyers
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Mixed Layer ◽  
Heat Budget ◽  
Sea Surface ◽  
Surface Mixed Layer ◽  
Horizontal Advection ◽  
Cold Anomaly ◽  
Sst Anomalies

Abstract Using results from the Simple Ocean Data Assimilation (SODA), this study assesses the mixed layer heat budget to identify the mechanisms that control the interannual variation of sea surface temperature (SST) off Java and Sumatra. The analysis indicates that during the positive Indian Ocean Dipole (IOD) years, cold SST anomalies are phase locked with the season cycle. They may exceed −3°C near the coast of Sumatra and extend as far westward as 80°E along the equator. The depth of the thermocline has a prominent influence on the generation and maintenance of SST anomalies. In the normal years, cooling by upwelling–entrainment is largely counterbalanced by warming due to horizontal advection. In the cooling episode of IOD events, coastal upwelling–entrainment is enhanced, and as a result of mixed layer shoaling, the barrier layer no longer exists, so that the effect of upwelling–entrainment can easily reach the surface mixed layer. Horizontal advection spreads the cold anomaly to the interior tropical Indian Ocean. Near the coast of Java, the northern branch of an anomalous anticyclonic circulation spreads the cold anomaly to the west near the equator. Both the anomalous advection and the enhanced, wind-driven upwelling generate the cold SST anomaly of the positive IOD. At the end of the cooling episode, the enhanced surface thermal forcing overbalances the cooling effect by upwelling/entrainment, and leads to a warming in SST off Java and Sumatra.

Atmospheric Cold Pools and Their Influence on Sea Surface Temperature in the Bay of Bengal

2021 ◽  
Vol 126 (9) ◽  
Author(s):  
M. S. Girishkumar ◽  
Jofia Joseph ◽  
M. J. McPhaden ◽  
E. Pattabhi Ram Rao
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Bay Of Bengal ◽  
Sea Surface ◽  
Cold Pools
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