INCOIS-GODAS-MOM: Ocean Analysis for the Indian Ocean: Configuration, Validation and Product Dissemination

The ocean covers approximately 71% of the earth surface and it significantly influences the global and regional climates and the weather and monsoon systems. Climate variability and its socio-economic impact clearly emphasizes the need to understand the system to enable better forecasts. Unlike land, where the operational networks of meteorological observations placed all over the world have enabled us to monitor changes in the global atmosphere, the global coverage of the subsurface observations in the ocean is largely under sampled. With the advent of Argo and moored buoy programs, there was a considerable increase in the amount of oceanic data during the last decade. However, the data is still inadequate to understand the dynamics and thermodynamics of the ocean on different spatial and temporal scale

What controls seasonal evolution of sea surface temperature in the Bay of Bengal? Mixed layer heat budget analysis using moored buoy observations along 90°E

Author Posting. © The Oceanography Society, 2016. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 29, no. 2 (2016): 202–213, doi:10.5670/oceanog.2016.52.Continuous time-series measurements of near surface meteorological and ocean variables obtained from Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) moorings at 15°N, 90°E; 12°N, 90°E; and 8°N, 90°E and an Ocean Moored buoy Network for Northern Indian Ocean (OMNI) mooring at 18°N, 90°E are used to improve understanding of air-sea interaction processes and mixed layer (ML) temperature variability in the Bay of Bengal (BoB) at seasonal time scales. Consistent with earlier studies, this analysis reveals that net surface heat flux primarily controls the ML heat balance. The penetrative component of shortwave radiation plays a crucial role in the ML heat budget in the BoB, especially during the spring warming phase when the ML is thin. During winter and summer, vertical processes contribute significantly to the ML heat budget. During winter, the presence of a strong barrier layer and a temperature inversion (warmer water below the ML) leads to warming of the ML by entrainment of warm subsurface water into the ML. During summer, the barrier layer is relatively weak, and the ML is warmer than the underlying water (i.e., no temperature inversion); hence, the entrainment cools the mixed layer. The contribution of horizontal advection to the ML heat budget is greatest during winter when it serves to warm the upper ocean. In general, the residual term in the ML heat budget equation is quite large during the ML cooling phase compared to the warming phase when the contribution from vertical heat flux is small.WHOI buoy deployment was supported by the US Office of Naval Research (grant no. N00014- 13-10453)

Tuning the Catalytic Activity of Graphene Nanosheets for Oxygen Reduction Reaction via Size and Thickness Reduction

Currently, the fundamental factors that control the oxygen reduction reaction (ORR) activity of graphene itself, in particular the dependence of the ORR activity on the number of exposed edge sites remain elusive, mainly due to limited synthesis routes of achieving small size graphene. In this work, the synthesis of low oxygen content (< 2.5 +/-0.2 at %), few layer graphene nanosheets with lateral dimensions smaller than a few hundred nm was achieved using a combination of ionic liquid assisted grinding of high purity graphite coupled with sequential centrifugation. We show for the first time, that the graphene nanosheets possessing a plethora of edges exhibited considerably higher electron transfer numbers compared to the thicker graphene nanoplatelets. This enhanced ORR activity was accomplished by successfully exploiting the plethora of edges of the nanosized graphene as well as the efficient electron communication between the active edge sites and the electrode substrate. The graphene nanosheets were characterized by an onset potential of -0.13 V vs. Ag/AgCl and a current density of -3.85 mA/cm2 at -1 V, which represent the best ORR performance ever achieved from an undoped carbon based catalyst. This work demonstrates how low oxygen content nanosized graphene synthesized by a simple route can considerably impact the ORR catalytic activity and hence it is of significance in designing and optimizing advanced metal-free ORR electrocatalysts.Comment: corresponding author: [email protected], ACS Applied Materials and Interfaces 201

Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005

Repeat near-fortnightly expendable bathythermograph (XBT) transects made along Kochi-Kavaratti (KK) shipping lane in the Lakshadweep Sea (LS) during 2002–2006 are examined to describe the observed year-to-year variability of upwelling during summer monsoon season (SMS). Among all the years, the upwelling characterized by up-sloping of 25°C isotherm is relatively weaker and persisted until November during SMS of 2005 and is stronger during the SMS of 2002. As a result of prolonged upwelling, the sea surface temperature has shown cooling extending into the postmonsoon season. The estimated marine pelagic fish landings along the southwest coast of India (SWCI) have also shown increase until December. The governing mechanisms both in terms of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005. The westerly wind bursts over the equator during the winter of 2004–2005 are both short-lived and relatively weaker triggering weaker upwelling Kelvin waves that propagated into LS in the following SMS of 2005. The observed distribution of negative sea surface height anomaly in the LS is relatively weaker during the SMS of 2005 and lasted longer. The correlation analysis suggests that the local alongshore WS off the SWCI and the remote forcing from the southern coast of Sri Lanka has greater influence on the observed interannual variability of upwelling in the LS when compared to the remote forcing from the equator

Comparative study of the implementation of tin and titanium oxide nanoparticles as electrodes materials in Li-ion batteries

Transition metal oxides potentially present higher specific capacities than the current anodes based on carbon, providing an increasing energy density as compared to commercial Li-ion batteries. However, many parameters could influence the performance of the batteries, which depend on the processing of the electrode materials leading to different surface properties, sizes or crystalline phases. In this work a comparative study of tin and titanium oxide nanoparticles synthesized by different methods, undoped or Li doped, used as single components or in mixed ratio, or alternatively forming a composite with graphene oxide have been tested demonstrating an enhancement in capacity with Li doping and better cyclability for mixed phases and composite anodes

Observed variability of chlorophyll-a using Argo profiling floats in the southeastern Arabian Sea

The time series of temperature, salinity, chlorophyll-a, particle scattering at 700nm, and dissolved oxygen obtained from Argo floats deployed in the southeastern Arabian Sea (AS), were used to investigate the variability of these quantities and the mechanisms that modulate them between March 2010 and March 2011. The observations show a persistent occurrence of a subsurface chlorophyll-a maximum (0.75-1mgm -3) near depths of 40-100m throughout the study period, just above the top of permanent thermocline and euphotic depth. The analysis shows that upward and downward movement of thermocline, which is primarily due to westward movement of low-mode baroclinic Rossby waves, significantly influences the depth of the subsurface chlorophyll maxima and its intensity. Further, the vertical movement of the thermocline significantly influences the depth of the oxycline in the AS. The mixed layer deepening associated with wind induced vertical mixing and convective overturning lead to near surface blooms during the summer and winter monsoons. The analysis clearly shows that, in addition to entrainment of nutrients from rich subsurface water in the near surface layer, vertical fluxes from the subsurface chlorophyll maximum also contribute significantly to mixed layer blooms. The availability of light also plays an active role in the mixed layer bloom, particularly during the summer monsoon season

Assessing the impact of various wind forcing on INCOIS-GODAS simulated ocean currents in the equatorial Indian Ocean

The Global Ocean Data Assimilation System configured at Indian National Centre for Ocean Information Services (INCOIS-GODAS) has been forced with satellite-based QuikSCAT gridded winds (QSCAT) to obtain accurate operational ocean analysis, particularly ocean currents, as compared to the default National Centers for Environmental Prediction-Reanalysis 2 (NCEP-R2) wind forcing in the tropical Indian Ocean (TIO). However, after termination of QuikSCAT mission in November 2009, an alternate wind forcing was required for providing operational ocean analysis. The present study examines the suitability of an Advanced Scatterometer (ASCAT)-based daily gridded wind product (DASCAT) for the INCOIS-GODAS. Experiments were performed by forcing INCOIS-GODAS with three different momentum fluxes derived from QSCAT, DASCAT, and NCEP-R2 wind products. Simulated ocean currents from these experiments are validated with respect to in situ current measurements from Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) buoys. Results suggested that the quality of simulated ocean currents from the daily DASCAT forcing is on par with the QSCAT forcing in the TIO, except for the equatorial Indian Ocean (EIO). Although QSCAT-forced current simulations are slightly better than DASCAT-forced simulations, both QSCAT and DASCAT provide a much better result than NCEP-R2. Our analysis shows that the better simulations of currents over the EIO, with the QSCAT forcing compared to DASCAT forcing, can be attributed to the smoothening of the wind field in the DASCAT compared to QSCAT. The impact of the error in the DASCAT on ocean current analysis is, however, limited to local scales and upper 100Â m of water column only. Thus, our study demonstrated that, in the absence of QSCAT, DASCAT is a better alternative for INCOIS-GODAS ocean analysis than the NCEP-R2