Tropical cyclones (TC) are one of the deadliest natural meteorological hazards and the most frequent cause of natural disasters. The El-Niño Southern Oscillation (ENSO), a tropical ocean-atmosphere interaction, is known to significantly impact cyclonic systems over global ocean basins. This study investigates the variability of TC activity in presence of ENSO over the North Indian Ocean (NIO), comprising of the Arabian Sea (ARB) and the Bay of Bengal (BOB) basins during the pre- and post-monsoon season, using accumulated cyclone energy (ACE) over the last 26 years. Our analysis reveals a significant rise in cyclone intensity over the past two decades, with eight of the ten most active years occurring since the 2000s. Total ACE over the NIO is found to be higher in La-Niña. Higher ACE observed over ARB is strongly associated with a combination of elevated sea surface height (SSH) anomaly and low vertical wind shear during the El-Niño episodes, with higher sea surface temperatures (SST) during the post-monsoon season. Whereas in the BOB, El Niño not only reduces ACE but also decreases basin-wide variability, and more pronounced effect during the post-monsoon season, coinciding with warmer SST and higher SSH along the coast during La-Niña.

Clew Bay is an important aquaculture production area in Ireland. In this study, we focused on a high-resolution simulation of the Clew Bay region based on a Regional Ocean Modelling System (ROMS). Freshwater discharges from eight rivers are included in the model and a wetting-drying scheme has been implemented. The Clew Bay model simulation was validated and calibrated with available observations (e.g., Acoustic Doppler Current Profilers (ADCP), vertical salinity and temperature profiles and tide gauge) in the geographic area of the model domain. High correlations were found between the model outputs and observed temperature, salinity and tide gauge water levels along with small Root Mean Square Errors. This indicates that the model was able to reproduce the oceanographic phenomena in the study area. The Taylor diagram analysis showed a high correlation coefficient (R=0.99) between the ADCP bottom temperature in the Inner Bay and the Clew Bay model, along with a small Centered Root Mean Square Error (RMSD =0.5 ◦ C). High correlation coefficients (R > 0.80) were found between the model and the two ADCPs for the zonal current component. There was a resemblance in structure between the model and the observed salinity profiles, indicating that freshwater was correctly implemented in the model. Moreover, the correlation coefficient between the model and the tidal sea surface height (SSH) was 0.99, with an RMSD of 0.09 m. We discovered that wind direction and speed have a significant impact on the bay's water inflow rate. The model outputs can be used to provide scientists, fishermen and decision-makers with hydrodynamic information on ocean conditions in the bay.

Higher-order topological insulators (HOTIs) are recently discovered topological phases, possessing symmetry-protected corner states with fractional charges. An unexpected connection between these states and the seemingly unrelated phenomenon of bound states in the continuum (BICs) was recently unveiled. When nonlinearity is added to a HOTI system, a number of fundamentally important questions arise. For example, how does nonlinearity couple higher-order topological BICs with the rest of the system, including continuum states? In fact, thus far BICs in nonlinear HOTIs have remained unexplored. Here, we unveil the interplay of nonlinearity, higher-order topology, and BICs in a photonic platform. We observe topological corner states which are also BICs in a laser-written second-order topological lattice, and further demonstrate their nonlinear coupling with edge (but not bulk) modes under the proper action of both self-focusing and defocusing nonlinearities. Theoretically, we calculate the eigenvalue spectrum and analog of the Zak phase in the nonlinear regime, illustrating that a topological BIC can be actively tuned by nonlinearity in such an HOTI. Our studies are applicable to other nonlinear HOTI systems, with promising applications in emerging topology-driven devices.