Picture of R/V Thompson in the Bay of Bengal. (Picture: San Nguyen)

In the pursuit of advancing our understanding of the monsoons and air-sea interaction, Tandon Lab members recently participated in a remarkable 45-day field campaign (following the pilot cruise in 2023) as part of the EKAMSAT (Enhancing Knowledge of the Arabian Sea Marine Environment through Science and Advanced Training) program on R/V Thomas G Thompson. This collaborative effort involved scientists from the USA and India, with the U.S. team funded by the U.S. Office of Naval Research and the Indian team supported by the Ministry of Earth Sciences (MoES). NASA-funded scientists also joined the research team to examine the ocean ecosystem. Originally planned for the Arabian Sea, the fieldwork had to pivot to the Bay of Bengal due to geopolitical tensions in the region . Around 60 scientists from various prestigious institutions, including the University of Washington, Scripps Institution of Oceanography, Woods Hole Oceanographic Institution, Columbia University, NOAA Center for Weather and Climate Prediction, University of Alaska-Fairbanks were part of this fieldwork. Indian institutions such as INCOIS, NIOT, NCMRWF, SAC-ISRO, and IITM-Pune also participated in the effort.

Objectives and Operations

The campaign aimed to study the atmospheric and oceanic boundary layer during the formation and destruction of a mini-warm pool in the Bay of Bengal. A mini-warm pool is a localized region of warm water that promotes water vapor convection, significantly impacting large-scale weather systems, such as the propagation of the monsoon. The team sought to observe the spatial extent of the mini-warm pool, the dynamics associated within it as this can affect regional weather patterns. The destruction of mini-warm pool or mixing of the warm water by the monsoon winds was also the focus of this study, amidst cyclones.

The fieldwork was split into two distinct legs. The first leg, from April 26 to May 14, 2024, focused on surveying the Bay of Bengal basin using an underway CTD (uCTD) to capture the spatial and vertical extent of the mini-warm pool across the Bay of Bengal basin. The team sailed from Chennai, India. Prof. Amit Tandon was one of the senior scientists on the first leg of the cruise, with Dr. Craig Lee from the University of Washington serving as the chief scientist. This phase also involved deploying autonomous instruments like wave-gliders, sea-gliders, and floats to measure various oceanographic parameters across a small part of the region.

EKAMSAT Leg-1 Science team (top). Prof Amit Tandon with AB Brian (bottom).

The second leg, from May 15 to June 15, 2024, led by Dr. Leah Johnson, focused on more detailed measurements using shipboard instruments like the FastCTD, Epsi, and T-Pads—cutting-edge devices developed by the Multi-scale Ocean Dynamics group at Scripps Institution of Oceanography. These instruments collected fine-scale ocean profiles. The configuration of the remote and shipboard instruments was aimed as to close the heat budget for the ocean and to understand the small-scale variabilities within the mini-warm pool’s dynamics. Radiosondes were also launched to collect atmospheric data, providing a more comprehensive view of how atmosphere evolved during the onset of the monsoon.

EKAMSAT Leg-2 Science team (Picture: San Nguyen)

Tandon Lab’s Contributions

Debarshi and Sid braving heavy rain and rough sea conditions during their deploying/monitoring instruments (Picture: San Nguyen and Kerstin Bergentz)

Sid Kerhalkar (PhD candidate at SMAST) and Debarshi Sarkar (PhD student in EAS program) from Tandon Lab braved challenging conditions—battling monsoon rains, tropical cyclones and high waves—while participating in watches to monitor, deploy, and recover shipboard instruments. Sid led the analysis of wave parameters during this fieldwork, while Debarshi contributed to the air-sea interaction analysis. In addition to their technical contributions, both were also involved in learning to launch radiosondes to capture atmospheric conditions during key periods of the monsoon.

Sid deploying the Radiosonde (Picture: Devmi Gamage)

Life at Sea

Beyond the scientific work, which bonded the team, life aboard the R/V Thomas G. Thompson was a unique experience. Daily science meetings provided an opportunity for the team to share findings from their earlier studies, discuss the upcoming weather and discuss new, exciting data collected during the cruise. Sid and Debarshi, along with their scientific contributions, added some flavor to ship life—quite literally! They were the part of the Indian-origin members of science team who volunteered to give the ship’s chefs a break for a meal, whipping up an Indian feast for the entire science team and crew (~60 people), which turned out to be a memorable event.

Sid (top left) and Debarshi (bottom left) busy cooking the Indian meal with the Indian team. Science team (right) seems happy with the meal serving. (Picture: San Nguyen and Sid Kerhalkar)

Sid also continued his hobby of video documentation, capturing the essence of life at sea and the exciting moments of the cruise—just as he had done in the previous year’s pilot expedition .

Underwater picture of Epsi profiler (top right), fishes (top left), T-Pads with fish in the background (bottom left) and a picture of sunset during the fieldwork (Picture: Sid Kerhalkar)

Despite the change in location, the EKAMSAT mission in the Bay of Bengal provided an invaluable opportunity to deepen the scientific community’s understanding of air-sea interaction during monsoon formation. The collaboration between international institutions and the deployment of cutting-edge technology highlighted the importance of such field campaigns in addressing complex climate phenomena. The data gathered will help inform future studies on how warm pools form, interact with atmosphere with respect to monsoon evolution, which eventually leads to its destruction, thus contributing to better weather forecasting globally and a deeper understanding of regional climate systems.

Prof Tandon presenting at MUST Day

The MUST project is a prestigious multi-departmental initiative within UMass Dartmouth, funded by the Office of Naval Research. Its primary objective is to advance cutting-edge research while cultivating a highly skilled workforce to support the needs of the U.S. Navy. UMass Dartmouth hosted the MUST Day event from 24th to 25 July 2024, providing an opportunity for professors and graduate students supported by the project to showcase their research and technical advancements through a series of 10-minute presentations and poster sessions.

The Tandon Lab made a strong impact at the event. Professor Tandon led the talk, ‘MITS: Sub-mesoscale and Mesoscale Interactions Study (SubMIST),’ and contributed to the presentations ‘Regional Ocean Turbulence from Long-Duration, Autonomous Observations’ and ‘Acoustic Rainfall Measurement on Global Drifters’.

Former master’s student Patrick Pasteris on behalf of the Aurelia team presented the on-going work, ‘Optimizing the Design of a Novel Upper Ocean Variable Buoyancy Vehicle.’ This began as a senior design project a few years ago and was also a topic of Patrick’s MS thesis. Current master’s student Ersen’S Joseph showcased his ongoing research on flow-structure interactions of grooved mooring lines through a poster presentation, while current PhD student Debarshi Sarkar discussed the errors and causes of the errors in atmospheric Reanalysis Products during the southwest monsoon season, in his poster session.

Patrick, Profs Tandon and Zhou presenting at MUST day

Many scientists, including Dr. Amit Tandon, collaborated on the paper: “Ocean surface radiation measurement best practices [Riihimaki et al. 2024]”. This article explores techniques and best practices for measuring downwelling shortwave (SWR) and longwave (LWR) broadband radiation, focusing on minimizing errors in these measurements.

Challenges in measuring upwelling SWR and LWR on oceans and land are also discussed, with suggestions for mounting sensors on towers in specific orientations to reduce shadows and enhance accuracy. The article highlights the importance of accurate surface albedo representation, particularly on sea and land ice, and compares the effectiveness of using UAVs versus land station towers for these measurements. It also reviews strategies for surface temperature measurements as an indirect tool for upwelling LWR assessments.
It recommends using instruments like pyrheliometer and a shaded pyranometer for SWR to avoid errors. For LWR measurements, the article advises using shaded devices to reduce solar leakage and recommends ventilated instruments to prevent dust contamination.
The article emphasizes best practices for installing and maintaining measurement systems and advises consistent sampling rates, careful maintenance to prevent errors from natural conditions. Despite following these practices, some errors may persist, which can be corrected through post-processing, calibration, and quality control schemes (emphasizing on using redundant measurements).
The article concludes by stressing the importance of adhering to global calibration standards and suggests field intercomparison between land and sea platforms to build a unified system for measuring climate variables. For the ease of the readers, the authors summarize each of the best practices in measuring ocean radiative heat fluxes in Table 5.
More information about the article can be found here.

Congratulations Dr. Tandon

Debarshi with his poster

Tandon lab PhD student Debarshi Sarkar presented his poster “Inaccuracies in Reanalysis Products: A Case Study in Arabian Sea from 2017 to 2018”, at the Sigma Xi poster exhibit, UMass Dartmouth on April 17^th and 18^th, 2024.

(L-R) Dr. Amit Tandon, Dr. Ruolin Zhou, Dr. Lauren Freeman, Dr. Oliver Sun and Patrick Pasteris with Aurelia

After a successful proposal to the University of Massachusetts Dartmouth Marine and Undersea Technology Program V (MUST V), Tandon Labs kicked off its first meeting for the continued development  of the Aurelia Upper Ocean Profilers. In attendance were two NUWC partners Lauren Freeman and Oliver Sun, the co-principal investigators Dr. Amit Tandon and Dr. Ruolin Zhou, as well as Research Technician and Aurelia inventor Patrick Pasteris.

The kickoff meeting signifies the beginning of 3 years of funding towards the continue development of the Aurelia UOP, which is a low-cost ultra-lightweight buoyancy vehicle being developed at University of Massachusetts Dartmouth. The profiler is focused on the upper 200m of the ocean and is meant to be an inexpensive alternative to the high-cost deep ocean profilers currently being deployed.

Sid presenting at 3 MT thesis competition

Sid Kerhalkar recently participated in a 3 MT thesis competition held in Grand Reading Room at UMass Dartmouth. Organized by Office of the Associate Provost for Graduate Studies, Three Minute Thesis (3MT®) is a research communication competition which challenges graduate research students (PhD and Masters by Research) to present a compelling oration on their thesis topic and its significance in just three minutes.  The competition develops academic, presentation, and research communication skills and supports the development of research students’ capacity to effectively explain their research in language appropriate to a non-specialist audience.

It was indeed an interesting experience for Sid to narrow his research within a 3 minute pitch.

On March 27, 2024, the Inter-campus Marine Science (IMS) of University of Massachusetts (UMass) hosted an symposium at the School for Marine Science and Technology (SMAST). The event brought together students and faculties from various UMass campuses to showcase their latest findings and innovations in marine science. One of the highlights of the symposium was Sid Kerhalkar (a 5^th year PhD candidate in the Tandon Lab), who was invited as a plenary speaker. Sid captivated the audience with his talk on the physics of hurricanes, drawing on insights from our recently concluded field trip to the Arabian Sea where we sampled the ocean post-hurricane (read more about the field campaign here).

Sid Kerhalkar presenting a plenary talk

Debarshi Sarkar (1^st year PhD student) presented his research on biases in reanalysis fluxes in the Arabian Sea through a compelling poster and a lightning talk. His work with Sid and Dr. Tandon as co-authors shed light on the biases in the Arabian Sea meteorological and flux variables.

Debarshi Sarkar presenting a lightning talk on his research

In addition to his plenary talk, Sid was voted with the best “Marine-Science” themed photo award in the symposium’s photo contest. Sid’s winning photograph captured the most essential instrument associated with oceanography, the CTD rosette. Overall, the UMass IMS symposium proved to be a fruitful gathering for the Tandon lab members.

Sid’s photo contest winning picture!

Members of Tandon lab and Mahadevan lab after the group meeting at SMAST

On March 15, 2024, Tandon Lab welcomed members from the Mahadevan Lab (Drs Amala Mahadevan, Alex Kinsella and Nihar Paul) for a collaborative group meeting. The session proved to be a melting pot of expertise, with members engaging in lively discussions spanning a broad spectrum of research areas. From the intricacies of clouds and atmospheric convection to the dynamics of air-sea interaction and ocean transport, every facet of ocean and atmospheric science found representation. The dialogue extended to topics as diverse as hurricane wakes, mooring designs for right whale monitoring, and beyond. This convergence of minds highlighted the commitment to interdisciplinary collaboration, laying the groundwork for future projects, innovations in understanding and addressing complex issues in ocean research.

In February 2024, the vibrant city of New Orleans became the focal point of ocean, atmosphere and marine biosphere research as Dr. Tandon and Sid (a PhD candidate in Tandon Lab)  participated in the prestigious Ocean Sciences Meeting. This gathering, organized by AGU, ASLO and TOS, and renowned for its interdisciplinary approach to marine research, provided a platform for scientists and scholars to share insights and innovations shaping the future of oceanography.

Dr Amit Tandon and Sid Kerhalkar at OSM 2024

Dr. Tandon presented a poster on reanalysis flux biases in the Arabian Sea. Drawing on research conducted by his PhD student, Debarshi (who could not attend due to class schedules), Dr. Tandon shed light on the biases in the Arabian Sea meteorological and flux variables, which could play a significant role in the forecasting errors in sub-seasonal to seasonal weather over Indian subcontinent. The poster sparked discussions and offered valuable perspectives for identifying and addressing biases in reanalysis fluxes, a critical aspect of understanding air-sea coupling. Dr Tandon was also a co-author on 6 other presentations/posters.

Dr Amit Tandon explaining the poster

Sid Kerhalkar presenting a talk

One of those included Sid, who talked about Hurricane wake recovery in the Arabian Sea. His presentation highlighted one-of-a-kind observational field campaign, which braved high waves to sample the hurricane wake and showcase the role of wind and density gradients coupling to drive lateral  processes to recover the wake. Sid’s insights stirred up an interesting conversation among experts, who initially believed that surface forcing was the only important process in the recovery of the wake.

The Ocean Sciences Meeting served as a melting pot of ideas and collaborations, where Dr. Tandon, Sid, and countless other researchers (including former members and collaborators of Tandon Lab) exchanged knowledge and forged partnerships for future research in marine science.

Dr Tandon and his extended group consisting of collaborators, students, former students and post-docs.

Dr Tandon with some of EKAMSAT Team

In a pioneering mission, a group of researchers (including Dr Amit Tandon) participating the Monsoon Intra-Seasonal Oscillations in the Bay of Bengal (MISO-BOB) field campaign, funded by the US Office of Naval Research, has provided groundbreaking insights into the tropical supercluster dynamics over the equatorial Indian Ocean.

In a study led by Dr Phadtare from University of Notre Dame, observations were collected using a WC-130J aircraft operated by Air Force’s 53rd Weather Reconnaissance Squadron, which delved into the heart of the action during the summer monsoon seasons of 2018 . Dropsonde observations revealed a captivating variance of zonal winds within the supercluster. The upper troposphere favored easterlies, while the lower troposphere exhibited prevailing westerlies, creating a unique atmospheric stratification just below the 0°C level.

Of particular interest was the cold pool at the center of the supercluster. It maintained a consistent easterly component, with the coldest temperatures registering a 2.5°C drop at the center. The depth of the cold pool varied, reaching its deepest at the rear/western end and shallower at the front/eastern end, measuring at around 300 meters. A key revelation was the identification of the level of free convection (LFC) at the front end. On the eastern flank, researchers observed zonal convergence between the westerlies within the supercluster and ambient easterlies at lower tropospheric levels. This suggested the uplifting of conditionally unstable air parcels above LFC due to convergence, rather than the influence of the cold pool.

Conversely, the western flank exhibited low-level zonal divergence, further supporting the concept of ‘self-similarity’ between mesoscale convective systems and large-scale waves.

The MISO-BOB campaign’s findings provide a leap forward in our understanding of monsoon intra-seasonal oscillations. The data obtained from these aircraft observations holds promise for refining climate models and advancing our ability to predict tropical weather patterns, contributing to more effective global weather predictions in the future.

More information about this article can be found here. Congratulations Dr Phadtare and team!

A schematic of the observations taken by the WC130J aircraft in the supercluster. (Adapted from Figure 10 of Phadtare et al. 2024)