Fingerprints of El Niño Southern Oscillation on global and regional oceanic chlorophyll-a timeseries (1997-2022).

With the advancement of present-day ocean color satellites, the spatiotemporal variations of oceanic Chlorophyll-a (Chl-a) concentration, a proxy for phytoplankton population, can be monitored at regional and global scales. Estimating long-term changes in Chl-a concentration, however, is mainly constrained by the limited availability of ocean color data and the significant influence of climate oscillations like the El Niño Southern Oscillation (ENSO). In this study, we investigate the influence of ENSO on regional and global Chl-a timeseries using two ocean color datasets spanning from September 1997 to December 2022.

Global wave number-4 pattern in the southern subtropical sea surface temperature.

Exploratory analysis using empirical orthogonal function revealed the presence of a stationary zonal wavenumber-4 (W4) pattern in the sea surface temperature (SST) anomaly in the southern subtropics (20°S-55°S). The signal over the Southern subtropics is seasonally phase-locked to the austral summer and persists up to mid-autumn. Thermodynamic coupling of atmosphere and the upper ocean helps in generating the W4 pattern, which later terminates due to the breaking of that coupled feedback.

Dynamic and thermodynamic upper-ocean response to the passage of Bay of Bengal cyclones 'Phailin' and 'Hudhud': a study using a coupled modelling system.

Understanding the upper-ocean response to tropical cyclones (TCs) in terms of sea surface temperature (SST) cooling is of prime importance in the prediction of TC intensity. However, the magnitude of cooling during the passage of TC varies depending on storm characteristics and pre-existing upper-ocean conditions such as the presence of ocean eddy and upper-ocean stratification. The present study investigates the upper-ocean response to two post-monsoon Bay of Bengal (BoB) cyclones, Phailin (October 2013) and Hudhud (October 2014), those followed almost a similar track, in association with pre-existing oceanic conditions using a fully coupled ocean-atmosphere modelling system.

Potential generation sites of internal solitary waves and their propagation characteristics in the Andaman Sea-a study based on MODIS true-colour and SAR observations.

The presence of large-amplitude Internal Solitary Waves (ISWs or solitons) is quite common in the Andaman Sea, located in the north-eastern Indian Ocean basin. ISWs are known to induce strong vertical velocities which can play an essential role in the mixing transport of nutrients and are proven hazardous to offshore oil platforms. The surface signatures of ISWs can be detected using remote sensing instruments like Synthetic Aperture Radar (SAR) and sunglint true-colour images.

Assessment of water quality using multivariate statistical techniques in the coastal region of Visakhapatnam, India.

The present study was intended to develop a Water Quality Index (WQI) for the coastal water of Visakhapatnam, India from multiple measured water quality parameters using different multivariate statistical techniques. Cluster analysis was used to classify the data set into three major groups based on similar water quality characteristics. Discriminant analysis was used to generate a discriminant function for developing a WQI.