Abstract This study presents the observation and evaluation of a meteotsunami in the Indian Ocean triggered by the Hunga‐Tonga volcanic eruption. The event was detected through tide gauges and bottom‐pressure recordings across the Indian Ocean, with an amplitude of 10–15 cm, lasting for a few days. A numerical model was used to understand the ocean's response to meteotsunami and evaluate the dynamics behind it. The model results show that the sea‐level oscillations result from the ocean waves generated by a propagating Lamb wave. In addition to interaction with bathymetry, refracted and reflected waves also determine the sea‐level variability. Our analysis shows that bathymetric slope plays a vital role in near‐shore processes. The spectral and spatial characteristics of the meteotsunami were reminiscent of seismic tsunamis. Our research on this rare event elucidates the unresolved issues and eventually leads to designing a blueprint for future observation and modeling of meteotsunamis and seismic tsunamis.

The vertical structure of chlorophyll in stratified oceanic waters exhibits a maximum substantially below the surface, known as the subsurface chlorophyll maximum (SCM). In the southern Bay of Bengal (BoB), a 12-day high-resolution time-series observation at 89 degrees E and 8 degrees N, during the 2016 summer monsoon showed that the SCM was located within the barrier layer (BL) and the euphotic layer. The strong BL (N2 = 3 x 10-4 s-2) located between 30 to 70 m, associated with a low salinity (<33.8 psu) water near the surface, maintained the stratification and the SCM. This SCM oscillated diurnally with an amplitude of 0.1 to 0.2 mg m-3. The lowest values of average chlorophyll in the SCM occurred around 06:00 hours (local time) and reached a maximum around 16:00 hours, four hours after the maximum in surface shortwave radiation. A coupled physical-biogeochemical one-dimensional model was used to examine the formation, maintenance and diurnal variability of the SCM in the southern BoB. The wind speed (<10 m s-1) that prevailed in the region during the weak phase of the monsoon was insufficient to break the BL and cause a surface bloom. The model results revealed that the surface shortwave radiation drove the diurnal cycle of the growth rate of phytoplankton at the SCM, hence the diurnal cycle of phytoplankton biomass and chlorophyll. The model's control simulation showed the dominance of small phytoplankton, and its growth rate was limited by light and nutrients at the SCM. Whereas, in the ML, the phytoplankton growth rate was limited by nutrients. In the model, the regenerated production supported around 60% of the chl-a at the location of SCM. The subsurface high-salinity core, a prominent feature in the southern BoB, did not influence the SCM. This paper offers new insights into understanding the SCM formation, maintenance and diurnal variability in stratified tropical oceans.

The Hunga Tonga Volcano in the southwest Pacific islands of Tonga erupted in January 2022. The massive explosion resulted in the generation of Lamb waves that propagated globally with a speed of ~ 300m/s and generated a tsunami that has affected numerous Pacific countries. In this study, we use observations and a numerical model to show the impact of this volcanic eruption on the Indian coastline. The Lamb wave took roughly 10 to 11 hours to reach the Indian coast, as observed in atmospheric pressure at mean sea level. Further, the signatures of high-frequency sea-level perturbations were observed from coastal tide-gauge networks along the Indian coastline. Our analysis shows that sea-level oscillations with considerable amplitude (10-20 cm) were observed along the Indian coastline during this period. The predominant frequency and amplitude, and oscillation were different at different locations. Further, an asymmetry between east and west coast stations was observed in the nature of high-frequency oscillations forced by the Hunga Tonga volcanic eruption. Finally, a numerical model was utilised to demonstrate how topography contributes to the observed sea-level disturbances. The model simulations imply that bathymetry is crucial to the observed sea-level variability. Thus, a 12000 km away event has significantly impacted the sea level along the Indian coastline. This work paves the way for understanding the importance of high-frequency variabilities along the Indian coastline and discusses the necessity to enhance the capability of our early warning systems by incorporating these variabilities.

Estuaries on the Indian subcontinent are influenced by the Asian Summer Monsoon and show strong seasonality. As a result, these estuaries are often referred to as monsoonal estuaries (Vijith et al., 2009). The seasonal cycle is superposed with intra-seasonal oscillations (ISO) with periods ranging from 10 to 90 days. Due to the lack of high-resolution data in Indian estuaries, even while the seasonal cycle of monsoonal estuaries is comparatively well understood, the intra-seasonal variability has not yet been examined. The active-break monsoon spells drive quasi-biweekly oscillations (10--20 days) within the ISO, and oscillations of 30–60 days are present due to northward-moving cloud bands. In this study, we use high-resolution salinity, temperature and sea level measurements from the Cochin estuary, located on the southwestern coastal plain of India, to investigate the ISO-related variability. The spectral analysis of the sub-tidal signals of salinity, temperature and sea level shows that ISO exists year round (December 2019 to May 2021). During the dry season (December to April), the salinity was on an average of 30 PSU, and the amplitude of ISO was from 3 to 5 PSU. In the wet monsoon season, the amplitude of ISO varies around 5 to 10 PSU. The temperature, sea level, and precipitation spectrum also exhibited similar patterns in the wet season. The coherence of salinity with sea level and precipitation is also quantified. ReferenceVijith, V., Sundar, D., Shetye, S.R., 2009. Time-dependence of salinity in monsoonal estuaries. Estuar. Coast. Shelf Sci. 85, 601-608. . http://dx.doi.org/10.1016/j.ecss.2009.10.003

There is a clear distinction in the feeding habits of fishes between the northeastern and southeastern Arabian Sea (west coast of India) - the north is carnivorous, and the south is planktivorous -, but such a distinction is not available for the western Bay of Bengal (BoB; comprising the east coast of India and the coasts of Sri Lanka and Bangladesh). We address this question by using publicly available landing data of finfishes for the four Indian states (Tamil Nadu, Andhra Pradesh, Odisha, and West Bengal) located along the western boundary of the BoB. Our analysis shows that the southwestern BoB is rich in fisheries and is more planktivorous compared to the northwestern BoB, which is more carnivorous. North-south variability exists even within the group of fishes such as anchovies and carangids. The meagre landing information for Sri Lanka and Bangladesh suggests that they show planktivorous and carnivorous characteristics of the southwestern and northwestern BoB, respectively. We show that monthly data and clarity on where the fish were caught are necessary to link the climatic conditions to the fishery along the western BoB. The landings on the Arabian-Sea and Gulf-of-Mannar part of the Tamil Nadu coast must be separated from the landings on its BoB coast. This separation can not be done with existing landing data and should be the first step in analysing fisheries data from the western BoB. The challenges in delineating the distribution of finfishes using available data illustrated here deliver guidance for future data collection and analysis at higher spatial and temporal scales for sustainable fisheries resource management in the region.

In the Indian Ocean (IO), the annual and semiannual oscillations of the sea surface temperature (SST) contribute more than 80% of the total variance. It is known that the SST in the tropical IO has warmed at a rate of 0.15 degrees C/ decade since 1979. However, such an estimate of the decadal trend of the annual and semiannual harmonics of SST remains unknown, despite being a strong component of the SST signal. Here we use a widely accepted data product (TropFlux) to quantify the annual and semiannual harmonics in the tropical IO for the first time. The northern IO has a distinctly strong semiannual cycle (1-1.8 degrees C), which is showing an amplifying trend (0.04 degrees C/decade) since 1979. Furthermore, a damping trend in annual amplitude exists over much of the IO, except along the northwestern Bay of Bengal, the Seychelles-Chagos thermocline ridge, the Persian Gulf, and the Indonesian throughflow region. The estimated damping of the annual amplitude is highest over the Arabian Sea. In contrast, the southern tropical IO has a predominant annual cycle, the amplitude of which has weakened during 1979-2018. In the north IO, net air-sea heat flux and vertical processes show a dominant semiannual harmonic oscillation similar to SST. Additionally, the annual amplitude is influential over southern IO. Horizontal advection contributes significantly along the boundary-current regions and the western equatorial IO. Our analysis of combined annual and semiannual cycles shows significant warming in the tropical IO during October-November and cooling during July-August owing to the amplification of semiannual oscillation. These changes in the SST can influence air-sea interaction processes such as cyclogenesis and monsoon.

The West India Coastal Current (WICC) flows southward (northward) during summer (winter). We examine the nature of circulation in the region of WICC during an inter-monsoon period using hydrographic data collected during March 6–21, 1994, and archived 1994 daily altimeter data. The hydrographic data did not show any organized northward or southward flow, implying that the amplitudes of the Rossby and Kelvin waves that make the WICC were negligible. Instead, cyclonic and anticyclonic eddies, well recorded in altimeter data, dominated the circulation. Because eddies occur throughout the year, our analysis highlights the need to study their role in WICC all through the year.

Wind climate along the southwest coast of India (Kerala coast) has been analysed using 41 years of Climate Forecast System Reanalysis (CFSR) winds to delineate long-term trends and variability. The study reveals significant decreasing trends in annual mean wind speeds, of the order of -2.0 to -2.5 cm center dot s(-1)center dot year(-1), for the period 1979-2019. Southwest monsoon has contributed the highest weakening trends (-3.0 to -4.0 cm center dot s(-1)center dot year(-1)) due to significant decrease in the southwesterly/westerly wind speeds. The wind climate and trends during the northeast monsoon and premonsoon seasons have been characterized largely by the prevalence of sea breeze and shamal-makran wind systems. We find that the intensity of both sea breeze and shamal-makran wind systems reduces from north to south along the Kerala coast, which is in consistent with the earlier studies. Decadal oscillations in wind speeds, driven by the decadal variability in large-scale atmosphere-ocean circulations, are evident. Recent changes in the frequency of occurrence of Indian Ocean Dipole in the Indian Ocean have determined the overturning trends since 2010, and resulted in increasing trends in the current decade along the central and northern coasts of Kerala. Furthermore, interannual variability in wind speeds has been linked to the El Nino-Southern Oscillations (ENSO) and Indian Ocean Dipole (IOD).

The climatologically averaged sea surface height anomaly (SSHA) during the summer monsoon in the Bay of Bengal (BoB) shows two prominent negative anomalies, one in the southern BoB and another in the northern BoB. The occurrence of negative SSHA observed in the southern BoB has been extensively studied and is linked to Sri Lanka Dome (SLD), whereas negative SSHA observed in the north has received less attention. A pronounced thermal dome develops in the northern BoB with its mean position between 86-89oE and 16-19oN, as shown by the doming of isotherms. We refer to this oceanic thermal dome as the northern BoB Dome (NBD). The present study focuses on the evolution of the NBD using observation and a coupled OGCM-biogeochemical model. The formation of NBD occurs during the summer monsoon (May - September), at a time when the wind stress curl is positive. Interestingly, the cyclonic curl is positive in the entire northern BoB, yet the negative SSHA is confined to a small region. Our analysis shows that strong stratification in the northern BoB inhibits the entrainment of the cooler-nutrient-rich subsurface waters to the surface during the event of dome formation. Consequently, the mixed-layer temperature in the NBoB region stays above the temperature criteria for active convection (>28 oC). Further, the inhibition of entrainment of nutrients causes the NBD region to be lower in productivity than the SLD region, as seen in chlorophyll distribution. We compare the NBD's heat and nutrient budget with the SLD and show that the near-surface stratification differences make the two domes distinct from each other.

Seasonal variability of the vertical structure of chlorophyll-a (chl-a) in the central Arabian Sea is described using seasonal climatology from bio-Argo floats. A quarter-degree resolution coupled OGCM-ecosystem model is employed to explain the physical and biogeochemical processes that determine the observed seasonality of the chl-a profiles. The most prominent feature of the chl-a is that seasonal surface bloom (chl-a > 0.25 mg m(-3)) occurs during the winter (November-February) and summer (June-September) monsoons. A sub-surface maximum (SCM) in chl-a occurs at a depth of about 60 m during the spring (March-May) and fall (October) oligotrophy. The SCM is absent during the peak of winter and summer bloom. The model simulated the observed seasonal evolution of chl-a and physical variables. Nitrate budget analysis, using the model simulation, reveals that vertical entrainment of nutrients plays a vital role in supplying nutrients into the surface mixed layer (ML) during the summer forced by wind mixing and winter due to convective cooling at the surface. Mixing is critical than Ekman pumping during the summer and winter monsoons. Further, the horizontal and vertical advection of nitrate is weak. The model showed the dominance of small phytoplankton in the central Arabian Sea. Analysis of the growth rate equation in the model shows that during the seasons of bloom, nutrients are surplus in the ML, and the euphotic depth that is shallower than the mixed layer depth drives the vertical structure of chl-a. The limiting nutrient above the euphotic depth during the winter (summer) is iron (phosphate). During oligotrophy, the growth rate of phytoplankton in the ML (SCM region) is determined by nitrogen (iron) limitation.

This study investigates the variability and sources of Quasi-Biweekly (QB) oscillation (10-20 days) in coastal sea level along the western boundary of the Bay of Bengal (BoB) using tide-gauge data and simulations from a very high-resolution regional model. Observations show most significant spectral energy in the QB band (similar to 12 days) exists in the northernmost location (Paradeep) with an amplitude of about 5-10 cm in sea level and energy in this band decreases equatorward along the coast. The QB oscillations in sea level contribute up to 16%-36% of the total subtidal sea-level variability in the western BoB and these oscillations are more pronounced during June-November. It is observed that sea-level oscillations in the QB band propagate equatorward along the east coast of India as coastal-trapped waves with a phase speed of about 2-4 ms(-1) and this speed is consistent with the theoretical estimates. Our study revealed that the strong QB winds found in the northern BoB are one of the forcing factors that excite QB oscillation in sea level in the western BoB. Further analysis using numerical simulations shows that the QB sea level propagating from the equatorial Indian Ocean and QB oscillation generated by strong winds associated with the tropical cyclones formed in the BoB also contribute to QB coastal sea-level fluctuations in this region.

Signatures of Rossby waves that are evident in satellite ocean colour data in the southeastern Arabian Sea (SEAS) are more prominent during the winter than the summer monsoon. During the winter, the sea level is high, and the conditions are less conducive for the injection of nutrients through the eddy-pumping mechanism. In this study, we use satellite observations and a physical-ecosystem model to examine the role of horizontal advection associated with Rossby waves in enhancing chlorophyll concentration in the SEAS. Zonal advection dominates over meridional advection, and its effect is more prominent in the south of Indian subcontinent and west of the Maldives. Except along the coast and around the islands, the vertical processes are weak and do not lead to a substantial increase in chlorophyll. Model simulations show that the currents associated with the Rossby wave also transport nutrients and other physicochemical properties of water along the path of the wave. The advected water decreases the concentration of Arabian Sea High Salinity water mass and replenishes the oxygen in the oxygen minimum zone in the SEAS.

Sea surface temperature (SST) is a fundamental driver of tropical weather systems such as monsoon rainfall and tropical cyclones. However, understanding of the factors that control SST variability is lacking, especially during the monsoons when in situ observations are sparse. Here we use a ground-breaking observational approach to determine the controls on the SST variability in the southern Bay of Bengal. We achieve this through the first full closure of the ocean mixed layer energy budget derived entirely from in situ observations during the Bay of Bengal Boundary Layer Experiment (BoBBLE). Locally measured horizontal advection and entrainment contribute more significantly than expected to SST evolution and thus oceanic variability during the observation period. These processes are poorly resolved by state-of-the-art climate models, which may contribute to poor representation of monsoon rainfall variability. The novel techniques presented here provide a blueprint for future observational experiments to quantify the mixed layer heat budget on longer time scales and to evaluate these processes in models.

The northern Bay of Bengal receives a large amount of fresh water through river runoff and rainfall during the Indian summer monsoon (June-September). This fresh water spreads offshore and can modulate the upperocean chlorophyll via two processes: advection of river nutrients and inhibition of vertical supply of subsurface nutrients by increasing the stratification. We address these two processes during the summer monsoon of 2012 using hydrographic observations and a coupled physical-biogeochemical model. The observations show an increase in surface chlorophyll associated with the advection of a freshwater plume on the shelf. Near the slope, but over a cross-shore distance of similar to 70 km, a thin layer separates this elevated surface chlorophyll from the subsurface chlorophyll maximum layer (SCML). This separation disappears as the freshwater plume reaches the open ocean. The SCML shoals toward the coast and is absent on the shelf. Time-series observations from the open ocean also show an increase in chlorophyll in concurrence with the arrival of a freshwater plume. Simulations with a coupled physical-biogeochemical model show, however, that it is the wind-induced vertical processes that cause the increase in chlorophyll in the open ocean and not the nutrients brought by the horizontal advection of freshwater plumes. The increase in stratification only limits and does not completely inhibit the vertical supply of nutrients from the subsurface layers.

During the Bay of Bengal (BoB) Boundary Layer Experiment (BoBBLE) in the southern BoB, time series of microstructure measurements were obtained at 8 degrees N, 89 degrees E from 4 to 14 July 2016. These observations captured events of barrier layer (BL) erosion and reformation. Initially, a three-layer structure was observed: a fresh surface mixed layer (ML) of thickness 10-20 m; a BL below of 30-40-m thickness with similar temperature but higher salinity; and a high salinity core layer, associated with the Summer Monsoon Current. Each of these three layers was in relative motion to the others, leading to regions of high shear at the interfaces. However, the destabilizing influence of the shear regions was not enough to overcome the haline stratification, and the three-layer structure was preserved. A salinity budget using in situ observations suggested that during the BL erosion, differential advection brought high salinity surface waters (34.5 psu) with weak stratification to the time series location and replaced the three-layer structure with a deep ML (similar to 60 m). The resulting weakened stratification at the time series location then allowed atmospheric wind forcing to penetrate deeper. The turbulent kinetic energy dissipation rate and eddy diffusivity showed elevated values above 10(-7) W kg(-1) and 10(-4) m(2) s(-1), respectively, in the upper 60 m. Later, the surface salinity decreased again (33.8 psu) through differential horizontal advection, stratification became stronger and elevated mixing rates were confined to the upper 20 m, and the BL reformed. A 1D model experiment suggested that in the study region, differential advection of temperature-salinity characteristics is essential for the maintenance of BL and to the extent to which mixing penetrates the water column.

We use available data and model simulations to make a case for physical forcing of the spatial variation in the nature of fisheries off the west coast of India in the eastern Arabian Sea (EAS). The approach is heuristic, but builds the case on the basis of model simulations and well-established implications of specific physical processes for the marine ecosystem. We address three questions. First, we show that it is differences in the physical forcing lead to a carnivore-dominated fishery in the northeastern Arabian Sea (NEAS) and a planktivore-dominated fishery in the southeastern Arabian Sea (SEAS). In the NEAS, the growing season for phytoplankton is longer because the upwelling during the summer monsoon (June September) is followed by convective mixing during the winter (November February) monsoon. Detrainment, again leading to a phytoplankton bloom, follows the convective-mixing season. The long duration of the growing season permits the existence of a longer food chain, leading to a carnivore-dominated fishery. In the NEAS, the phytoplankton also tend to be small owing to weaker upwelling during the summer monsoon and limitations imposed by silicates, turbulence, and light during the winter monsoon. In the SEAS, the stronger upwelling implies larger phytoplankton that can be directly fed on by fish like the oil sardine. The growing season in the SEAS is also limited to the summer monsoon, predisposing the ecosystem towards a shorter food chain. Second, we show that it is the differences in physical forcing that lead to the weaker fishery in the central-eastern Arabian Sea (CEAS) compared to the SEAS. Though the growing season in both SEAS and CEAS is comparable, the upwelling is weaker in the CEAS, implying a limitation of nitrate and a dominance of small phytoplankton in contrast to the SEAS, where large phytoplankton dominate. Hence, the phytoplankton biomass is less in the CEAS compared to the SEAS and the region cannot support a fishery comparable to the SEAS. Third, we show that it is the difference in physical forcing that leads to a sharp decline in the catch of oil sardines from the SEAS to the CEAS even as the catch of mackerel does not change much. Not only does the stronger upwelling in the SEAS compared to the CEAS imply a larger size of the phytoplankton in the former, but the phytoplankton biomass is also higher in the SEAS. The zooplankton standing stock, as estimated using the backscatter measured by the acoustic Doppler current profilers (ADCPs) deployed on moorings, is determined more by the vertical movement of the depth of the 20 C isotherm (D20). Hence, the standing stock of zooplankton tends to be lowest when upwelling peaks, i.e., during the summer monsoon. This is also the time when the phytoplankton biomass peaks. The phytoplankton surplus is greater in the SEAS compared to the CEAS because of the stronger upwelling, which implies higher primary productivity and a shallower D20, in the SEAS. This phytoplankton surplus can be fed on by the oil sardine, which prefers diatoms. In contrast, the higher zooplankton standing stock in the CEAS competes with the oil sardine off Karnataka and Goa, where the mackerel, which feed on zooplankton, is the dominant fishery. The weaker upwelling implies lower primary productivity and a deeper D20 (higher zooplankton standing stock) in the CEAS. This limitation of the mature habitat by the physical forcing and the seasonal reversal of the currents limits the spawning regimes of these fish because the carnivorous (planktivorous) fish like the Bombay Duck (oil sardine) can spawn only in those regions from where they can make it to their mature habitat in the NEAS (SEAS).

The Bay of Bengal (BoB) plays a fundamental role in controlling the weather systems that make up the South Asian summer monsoon system. In particular, the southern BoB has cooler sea surface temperatures (SST) that influence ocean–atmosphere interaction and impact the monsoon. Compared to the southeastern BoB, the southwestern BoB is cooler, more saline, receives much less rain, and is influenced by the summer monsoon current (SMC). To examine the impact of these features on the monsoon, the BoB Boundary Layer Experiment (BoBBLE) was jointly undertaken by India and the United Kingdom during June–July 2016. Physical and biogeochemical observations were made using a conductivity–temperature–depth (CTD) profiler, five ocean gliders, an Oceanscience Underway CTD (uCTD), a vertical microstructure profiler (VMP), two acoustic Doppler current profilers (ADCPs), Argo floats, drifting buoys, meteorological sensors, and upper-air radiosonde balloons. The observations were made along a zonal section at 8°N between 85.3° and 89°E with a 10-day time series at 8°N, 89°E. This paper presents the new observed features of the southern BoB from the BoBBLE field program, supported by satellite data. Key results from the BoBBLE field campaign show the Sri Lanka dome and the SMC in different stages of their seasonal evolution and two freshening events during which salinity decreased in the upper layer, leading to the formation of thick barrier layers. BoBBLE observations were taken during a suppressed phase of the intraseasonal oscillation; they captured in detail the warming of the ocean mixed layer and the preconditioning of the atmosphere to convection.

A linear coastal-trapped-wave (CTW) model is used to examine the effects of large-scale winds, with time scale ranging from a few days to a few weeks, on the West India Coastal Current (WICC), particularly on the shelf off the central west coast of India. We show that unlike the seasonal cycle of WICC, which is primarily forced by the winds along the east coast of India, the high-frequency WICC is mostly driven by the west-coast winds. Nevertheless, the influence of winds as far as Sri Lanka and east coast of India cannot be neglected. Simple numerical experiments with the CTW model show that the strong current observed at Goa (15° N) compared to Bhatkal (13° N) and Jaigarh (17° N) is due to two factors: (1) the superposition of local and remote CTWs and (2) the widening of shelf width north of Goa, which decreases the amplitude of the currents poleward of Goa. If the local winds are weak, the amplitude of current decreases poleward due to friction, and the current at the south leads the north. We also note that the observed phase difference between sea level and alongshore current at Goa could be attributed to the propagation of remotely forced higher-order modes of CTWs.

The strong stratification of the Bay of Bengal (BoB) causes rapid variations in sea surface temperature (SST) that influence the development of monsoon rainfall systems. This stratification is driven by the salinity difference between the fresh surface waters of the northern bay and the supply of warm, salty water by the Southwest Monsoon Current (SMC). Despite the influence of the SMC on monsoon dynamics, observations of this current during the monsoon are sparse. Using data from high-resolution in situ measurements along an east–west section at 8°N in the southern BoB, we calculate that the northward transport during July 2016 was between 16.7 and 24.5 Sv (1 Sv ≡ 10 6 m 3 s −1 ), although up to ⅔ of this transport is associated with persistent recirculating eddies, including the Sri Lanka Dome. Comparison with climatology suggests the SMC in early July was close to the average annual maximum strength. The NEMO 1/12° ocean model with data assimilation is found to faithfully represent the variability of the SMC and associated water masses. We show how the variability in SMC strength and position is driven by the complex interplay between local forcing (wind stress curl over the Sri Lanka Dome) and remote forcing (Kelvin and Rossby wave propagation). Thus, various modes of climatic variability will influence SMC strength and location on time scales from weeks to years. Idealized one-dimensional ocean model experiments show that subsurface water masses advected by the SMC significantly alter the evolution of SST and salinity, potentially impacting Indian monsoon rainfall.

BAMS is looking for community snapshots from AMS members.Send to synoptics@ametsoc.org.Please include identifying information.Researchers ready a vertical microstructure profiler for deployment during the BoBBLE field experiment.Conducted in the southern Bay of Bengal onboard the R/V Sindhu Sadhana, the scientists were investigating oceanographic processes and their impact on the Asian monsoon.During BoBBLE, measurements were carried out using multiple platforms.For more details on the field experiment, see the article in this issue (p.