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The key role of oceans in the global climatic system can be accurately quantified by the measurement of CO $_{2}$ exchange across air–sea interface. The direction and magnitude of this CO $_{2}$ exchange are mainly governed by the gradient of partial pressure of carbon dioxide (pCO $_{2}$) at the air–sea interface. The sea surface pCO $_{2}$ is highly variable, primarily regulated by seasonal sea surface temperature (SST) and CO $_{2}$ (aqueous) concentration. In this paper, the moored pCO $_{2}$ observations from autonomous pCO $_{2}$ system deployed at 15  $^{\circ }$ N 90  $^{\circ }$ E in the Bay of Bengal (BOB) were used to derive CO $_{2}$ fluxes to examine variability over time scale at BOB. An attempt has also been made to develop a model using multiple linear regression (MLR) and support vector regression (SVR) to estimate the sea surface pCO $_{2}$ from space-based observations of SST and salinity. pCO $_{2}$ variability was primarily attributed to SST and CO $_{2}$ concentration changes. Derived fluxes showed that BOB is a net annual source (0.440 g-C/m $^{2}$ /year for year 2014) of CO $_{2}$ at mooring location with significant seasonality effects. For the estimation of surface pCO $_{2}$ , SVR model showed better results [root mean square error (RMSE) = 7.68 $\mu$ atm] in comparison to MLR model (RMSE = 12.36 $\mu$ atm). The seasonal climatological pCO $_{2}$ maps from September 2011 to February 2018 showed southward increase in pCO $_{2}$ in all seasons possibly due to southward increase in SST and less influence of river water. These pCO $_{2}$ maps can further be utilized in deriving CO $_{2}$ flux maps for BOB. [ABSTRACT FROM AUTHOR]

An investigation of the eddy and coastal Kelvin wave activities in the Bay of Bengal (BoB) is carried out during premonsoon season in two years of Indian summer monsoon deficit in June (2009 and 2012), occurred in the recent warming hiatus period. Using altimeter observations, our study reveals that over the northern BoB cyclonic eddy kinetic energy is reduced by 35% and 50% from the climatology during premonsoon seasons in 2009 and 2012, respectively, while the cyclonic eddy area is reduced by 18% and 24%, respectively. A concurrent reduction is observed in the first upwelling Kelvin wave (uKW) activities in the eastern equatorial Indian Ocean as well as in the coastal BoB for these years. The reduction in the generation of the first uKW in the eastern equatorial Indian Ocean is attributed to the westerly wind anomalies in January–March of these years. Additionally, meridional wind stress anomalies during March–April in these years are found to be southerly, causing anomalous coastal downwelling in the eastern rim of BoB. This coastal downwelling blocks the propagation of the first uKW. The decrease in the first uKW activities in the coastal waveguide of the BoB reduces the radiation of upwelling Rossby waves, thereby decreasing the cyclonic eddy activities in the northern BoB. The results from this letter could be helpful for further understanding of upper ocean mixing processes in the BoB during monsoon deficit years. [ABSTRACT FROM PUBLISHER]

This paper presents the first results on comparisons of Scatterometer Satellite-1 (SCATSat-1) derived wind datasets with the in situ, reanalysis as well as another operational scatterometer derived winds in the Bay of Bengal during the period November 2016–March 2017. The comparisons of daily gridded wind products of SCATSat-1 with buoys show good correlations (>0.83), higher skill scores (>0.92), and lower root mean square errors (RMSEs) of 0–2 m/s for wind speeds (WS) at the buoy locations. Similarly, the results corresponding to wind directions (WD) show higher correlations (>0.95), higher skill scores (>0.96), and relatively lower RMSEs (15–30°). Further, the intercomparisons of SCATSat-1 with Advanced Scatterometer and European Centre for Medium Range Weather Forecasts reanalysis winds show strong correlations for both WS (>0.85) and WD (>0.94). This paper also reports the capability of SCATSat-1 to capture three tropical cyclones Kyant, Vardah, and Mora during the period of study with the highest WS of 23.5 m/s. [ABSTRACT FROM PUBLISHER]

Remote sensing-based analysis has been carried out to study the impact of “Phailin” cyclone on ocean phytoplankton distribution off Odisha coast and on the northern Bay of Bengal water. Oceansat-2 Ocean Colour Monitor (OCM) and MODIS-Terra sensors-derived chlorophyll images have been generated over the study area during October 2013. There has been observation of drastic change in the chlorophyll concentration of the north-western Bay of Bengal water with effect of the cyclone “Phailin,” which hit Gopalpur, Odisha coast on 12 October night at around 21:00 h IST. The postcyclone images of Oceansat-2 OCM data and retrieved chlorophyll concentration were observed to be very high, \bf3.0 - 4.0\;\bfmg/m^\bf3 in coastal water, which was around \bf0.5 - 1.0\;\bfmg/m^\bf3 during precyclone. Similarly, the postcyclone chlorophyll was around \bf0.80 - 1.50\;\bfmg/m^\bf3 in the offshore water, unusually high compared to precyclone concentration (< \bf0.60\;\bfmg/m^\bf3). The cyclone track of India Meteorological Department (IMD) has been superimposed on chlorophyll images and observed as proxy along the chlorophyll front with algal bloom features. There has been observation of cooling in the northern Bay of Bengal and off Odisha coast with impact of the induced upwelling, entrainment and mixing of the water column, as evident from the sea surface temperature (SST) data analysis. Interesting features such as cold core eddies and fronts have been visualized. This study is important to assess the impact of Phailin cyclone on ocean productivity on the local and basin scale and its deviation from seasonal trend as well. [ABSTRACT FROM PUBLISHER]