SPRING 2026
Fridays at 11:00 am, Rosenstiel School Auditorium / Virtual Auditorium
(unless stated otherwise)
Jan 16: NO SEMINAR
Jan 23: NO SEMINAR (High-Performance Computing Town Hall)
Jan 30: NO SEMINAR
Feb 06: NO SEMINAR (Recruitment Weekend)
Feb 13: NO SEMINAR (Rosenstiel School Faculty Meeting)
Feb 20: STUDENT SEMINARS
Sam Ephraim (MPO)
Closed-to-Open-Celled Mixed-Phase Cloud Transition Over the Nordic Seas
Under High Aerosol Loading
Closed-cell to open-cell mixed-phased cloud transitions within marine cold air outbreaks (MCAO) remain challenging to model and predict, in part because underlying coupled processes (microphysics, turbulence, and radiation) remain poorly observed at process-level scales. While aerosol concentrations in the Arctic are typically low, the Cold Air Outbreak Experiment in the Sub-Arctic Region (CAESAR) observed a closed to open-celled transition within a MCAO over the Nordic Seas with boundary layer aerosol and cloud condensation nuclei concentrations surpassing 650 cm–3, likely sourced from industrial emissions in Siberia. We find that liquid-cloud processes govern the production of frozen precipitation, even at cloud temperatures colder than –15°C, pivotal for forming cold pools and initiating cloud breakup. High aerosol concentrations within a boundary layer containing a closed-celled convective cloud deck initially result in small drop sizes (cloud top effective radius of 6 µm), limiting riming efficiencies. Precipitation is all ice, with an initial dominant habit consisting of dendrites and aggregates. As closed-celled clouds deepen, aerosol depletes to concentrations of 380 cm–3 through precipitation scavenging and dilution with clean free tropospheric air, resulting in increased drop sizes. Increased riming efficiency increases the prevalence of rimed dendrites and small graupel (~1 mm) that reach the surface and form cold pools breaking up the cloud deck into open-celled convection. Depleted aerosol concentrations (~125 cm–3) within open-cells support larger drop sizes (15-30 µm) and sporadic in-cloud freezing drizzle. Heavy precipitation shafts contain abundant large graupel (~5 mm) with liquid equivalent precipitation intensities reaching 2 mm hr–1.
Ian Gifford (MPO)
ENSO Phase Prediction in a Warming Climate
Recent years have seen an apparent disconnect between oceanic signatures in the ENSO key monitoring region and the expected atmospheric response. Recent studies have concluded a new proxy for ENSO phase monitoring and prediction is necessary to accommodate an ocean whose tropics are warming too quickly for the use of decadal climatologies as a baseline to measure anomalous temperatures. Increased warming has led to an overestimate of the ENSO warm phase amplitude and consequently the expected impact patterns on global regions most sensitive to ENSO. Naturally, underestimates for the ENSO cold phase are inherent and have also been noted. This study examines the teleconnection capture ability between the traditional Oceanic Niño Index, and the newly developed relative Oceanic Niño Index. Also investigated are the equatorial Pacific zonal sea surface temperature gradient and the area of the equatorial Pacific cold tongue. The latter two indices feature the advantage of not requiring the use of long-term means. Statistical methods utilized include pattern correlation, which isolates expected patterns on ENSO sensitive regions as a response to equatorial Pacific Ocean surface conditions. Precipitation, geopotential height anomalies, and the Rossby wave source are used to diagnose each index's ability to represent the expected response from conditions in the equatorial Pacific.
Steven Akin (MPO)
Near-Inertial Wave Propagation in a Cyclonic Eddy Barrier Layer
Cyclonic eddies (CE) are common features in the Gulf that have been observed to affect anticyclonic eddy (AE) shedding, tropical cyclone (TC) intensity, and lateral transport of freshwater from the Mississippi River Plume. The literature suggests that wind-driven shear within a CE reaches a maximum at the base of the mixed layer (ML), often resulting in entrainment and cooling through near-inertial currents and shear instabilities. By contrast, barrier layers (BL) can form between the ML and isothermal layer (ILD) depths that can impede vertical motions and fluxes. In this scenario, the MLD is decoupled from the pycnocline (temperature and salinity), and wind-driven shear maxima are found at the depth of the maximum salinity gradient, often corresponding to the BL's lower interface. High-resolution observations of well-resolved near-inertial currents, buoyancy frequencies, and shear instabilities reveal enhanced stratification and the CE's positive relative vorticity modulated near-inertial wave propagation. That is, these energetic near-inertial wave packets impacted the BL's variability in the days following Hurricane Michael (2018). These results have important implications for TC development and upper-ocean mixing.
Feb 27: NO SEMINAR
Mar 06: Dr. Kathy Pegion
School of Meteorology, National Weather Center, University of Oklahoma
Guest of Emily Becker and Ben Kirtman
Sources of Predictability for Subseasonal Precipitation in South America
Recording Available at COMPASS ON DEMAND
This study investigates the sources of predictability underlying subseasonal precipitation skill over South America in existing subseasonal prediction systems. Using subseasonal re-forecasts from the NCAR-CESM2 model, we demonstrate that significant skill persists even when interannual variability is removed. The highest skill occurs during austral summer and spring. To isolate sources of predictability, we analyze a novel set of re-forecast experiments initialized with climatological atmosphere, land, and ocean states. Results indicate that atmospheric initial conditions are essential for achieving skill, while ocean initializations contribute to skill containing interannual variability, and land initializations contribute minimally to skill.
Canonical correlation analysis is used to identify the most skillful spatial patterns and associated time series during the high-skill seasons. The most skillful patterns in December-February are not independent of the South American dipole but also contain additional skill beyond the dipole. This additional skill is not associated with propagating tropical convection or sea surface temperature anomalies indicating that the Madden-Julian Oscillation, El Niño-Southern Oscillation, or South Atlantic SST variability are not the sources of predictability.
Instead, a wave-train-like structure extends across the South Pacific, resembling a Rossby wave response. Idealized experiments using a simplified atmospheric general circulation model show that this pattern can be reproduced by stationary tropical heating over the Maritime Continent, suggesting a dynamical link between tropical heating and South American precipitation variability on subseasonal timescales independent of ENSO and the MJO.
Mar 06 (4:00 pm): SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. William Johns
Department of Ocean Sciences, Rosenstiel School
Exploring Overturning Circulations Great and Small:
My 40 Years as a Seagoing Oceanographer
Recording Available at COMPASS ON DEMAND
Overturning circulations are key components of the earth's climate system, producing dense waters that fill the deep ocean basins as well as intermediate waters that derive from adjacent marginal seas. While I have had the opportunity to study a variety of ocean circulation problems, much of my work has focused on the measurement of overturning systems, including the large-scale Atlantic Meridional Overturning Circulation (AMOC) and (relatively) smaller-scale overturning systems such as those in the Red Sea and Persian Gulf. A key aspect of these overturning circulations is the entrainment of ambient waters into the descending gravity currents that spill from marginal seas into the oceans, which effectively controls the amount of deep water that is finally produced. In the Atlantic, the interaction of the AMOC with the wind-driven gyre circulation is also an interesting problem, as the upper limb of the AMOC has to navigate its way northward through the wind-driven gyres to reach the high-latitude regions where it is eventually transformed into deep waters. I will review some of the main findings that have come from RSMAES programs studying these problems, in collaboration with many other researchers both nationally and internationally.
Mar 13: NO SEMINAR (Spring Recess)
Mar 20: NO SEMINAR (Rosenstiel School Research Day)
Mar 27: NO SEMINAR (MPS Recruitment Event)
Apr 03: STUDENT SEMINARS
Katrina Simi (OCE)
Wave Energy Transformation of a New Type of Breakwater: The Seahive
Submerged breakwaters are often used as a base for coral outplanting because they offer stable environments for coral propagation. There is still a question of how these bases can be optimized – with design considerations of geometry and porosity – to foster coral reefs while efficiently reducing wave energy. In nearshore environments, porous breakwaters often experience internal sedimentation and biological interference, which can alter their porosity and wave dissipation capabilities over time. This study explores the efficacy of "Seahives", a modular hexagonal perforated structure, to be used as an artificial reef foundation which is designed to be stacked and arranged in various configurations. Nine model Seahives were placed in a 4-3-2 row pyramid shape. The perforations of this configuration were obstructed using tape to determine how porosity contributes toward the overall wave energy transformation over the Seahives. This experiment was conducted in the University of Miami's SUSTAIN tank (23 m L × 6 m W × 2 m H), a wind-wave tank equipped with 12 paddles capable of generating various wave conditions. Eight wave probes were deployed to measure wave surface elevation under shallow and intermediate wave conditions. At a 0.55 m water depth, wave heights of 0.06 m, 0.08 m, and 0.10 m were tested against wave periods of 1.0 s, 1.5 s and 2.0 s. The energy flux through the structure was calculated, and the nonporous and fully porous Seahive data were compared. The energy flux values demonstrated that there was greater dissipation when the Seahive perforations were left unobstructed, making porous Seahives the ideal choice for artificial reef foundations.
Paloma Cartwright (OCE)
Seasonal Variability of Water Mass Structure and Transport in the Florida Current
Paloma Cartwright¹, Christopher G. Piecuch², Guillaume Novelli¹, Rachel Bramblett¹, Lisa M. Beal¹
¹Rosenstiel School
²Woods Hole Oceanographic Institution, Woods Hole, MA
The Florida Current (FC) transports heat, salt, and other climatically important properties poleward as part of the Atlantic Meridional Overturning Circulation (AMOC). While Gulf Stream surface temperatures have been rising two to three times faster than the global ocean, volume transport has remained stable. Although variability of FC transport is well characterized by a multi-decadal submarine cable record, far less is known about variability in the water mass properties it carries. This study addresses that gap using shipboard hydrography and velocity data to examine variability from a water mass perspective. Potential density distinguishes Surface Waters (SW), Subtropical Waters (STW), and Antarctic Intermediate Waters (AAIW), while potential vorticity gradients separate STW into eastern and western components, revealing a mixing barrier within the current. We find seasonal variability is driven by wind-forced isopycnal heave. In summer, isopycnals lift, producing warmer SW, colder and fresher STW, and shoaling AAIW up the slope; in winter, isopycnals deepen, reversing these patterns. The recirculating component shows high volume but weak variability, while the overturning component drives the seasonal signal. On longer timescales, only SW transport increases significantly. These results suggest that enhanced transport of warm surface waters, independent of total volume transport, may drive rapid Gulf Stream warming. More broadly, a weakening AMOC may not imply a weaker Gulf Stream, as the overturning component can vary independently of total transport.
Hanna Chaja (ATM)
Detecting Gravity Waves in Stratocumulus Cloud Decks
Hanna Chaja, Mathieu Ratynski, and Brian Mapes
Department of Atmospheric Sciences, Rosenstiel School
Stratocumulus (SC) cloud decks play a central role in Earth's energy balance due to their strong radiative effects and coverage. Beyond their climatic importance, SC decks provide a natural visualization platform for internal mesoscale gravity waves, which would otherwise be invisible. These waves, typically with wavelengths on the order of 10² km or larger, manifest as modulations in cloud brightness and structure. Their sources, amplitudes, and propagation characteristics remain poorly understood due to observational challenges and limited representation in global models. This study proposes a novel approach to detecting gravity wave signatures in SC decks using Particle Image Velocimetry (PIV) applied to sequential satellite image pairs. After preprocessing to enhance cloud-texture variability, PIV is used to track evolving cloud features and retrieve high-resolution motion vectors. These motion estimates are then used to derive divergence patterns and associated vertical motions linked to gravity wave activity. We find that PIV can detect the imprint of gravity waves in SC decks even when modulations in cloud brightness are weak. This preliminary work aims to lay the groundwork for a quantitative estimate of wave characteristics, sources, and potential long-range predictability of gravity wave events.
Apr 10: STUDENT SEMINARS
Katrina Rosing (OCE)
Using eDNA to Compare Seawater Microbiomes
Near Reefs and Control Sites off the Gulf Coast
Similar to their shallow counterparts, mesophotic corals provide nutrient cycling, habitat, and play a large role within the biogeochemistry of their environment. Within these ecosystems, the coral holobiont consists of unique bacterial communities that differ among the mucus, the tissues, and the surrounding water column. Some of these bacterial relationships have been shown to be consistent among corals, and ongoing studies are helping to determine which microbial relationships are biologically important. Additionally, understanding the effects of abiotic factors on microbial populations is becoming more pressing as climate change continues to play a critical role in changing environmental parameters. Using environmental DNA (eDNA) collected from seawater near reefs, we can compare the microbiomes of seawater from coral reefs and control sites off the Gulf coast. Coral eDNA was collected via CTD by NOAA AOML during a cruise from 13 September to 21 October 2021 in the Gulf of Mexico. Using the publicly available data on the NCEI database, analysis of the deep and shallow microbial communities in the Gulf showed that coral-influenced sites harbored distinct bacterial assemblages with eight coral-specific core taxa and significantly different community composition. Shannon diversity was significantly elevated at coral sites in deep waters (220-250 m) but not shallow waters (60-95 m), demonstrating depth-stratified coral-microbe associations in mesophotic reef ecosystems. Characterizing the microorganisms within these reefs allows us to better understand reef microbe associations and potentially reveal significant microbial relationships.
Gabrielle Ricche (OCE)
Quantifying Environmental Forcing on North Atlantic Iceberg Drift
Through Kinematic Regression Analysis
Iceberg drift in the Arctic and North Atlantic is governed by ocean currents and surface winds, yet the relative contributions of these forcing factors remain poorly constrained across different iceberg types, limiting the reliability of operational drift forecasts. While the commonly cited 2% wind rule provides a useful baseline, it has not been systematically evaluated across iceberg size and shape classes or validated against in situ observations. To address this gap, complex multiple linear regression was applied to GPS beacon trajectories from the 2019 C-CORE MTEQ-IIP campaign off Newfoundland and Labrador, using ERA5 winds and HYCOM ocean currents as forcing inputs, with current forcing depth-weighted over the estimated keel. Icebergs are found to closely track the underlying ocean current, with wind playing a secondary but measurable role that varies with iceberg type. Shape proves a stronger predictor of model skill than size, with dome and pinnacle icebergs best predicted and blocky and tabular forms performing worst. The model systematically underpredicts drift under wind-dominated conditions, and unexplained residuals grow with iceberg size, pointing to unresolved processes such as inertial oscillations and current underrepresentation at depth. These patterns suggest that bulk forcing assumptions obscure meaningful structure in iceberg dynamics, with geometry exerting a stronger control on drift predictability than scale alone. Resolving wind and current contributions across iceberg types provides observation-based constraints that identify where existing drift model assumptions are most likely to fail.
Snigdha Samantaray (MPO)
The Dynamics of Precipitating Water Vapor Lakes
Over the Western Equatorial Indian Ocean
Over the western equatorial Indian Ocean, synoptic scale high column water vapor (CWV) lakes stand out in stark contrast to the typically drier zones, maintaining coherence for several days and often bringing rain to the African coast. Our study explores the persistence and motion of water vapor lakes about its margin. We analyze their maintenance and propagation using a boundary focused moisture budget applied to 55 mm CWV contours identified from MERRA-2. The lake margin is treated as a moving interface whose normal velocity is determined by local tendencies including horizontal and vertical transport of moist air, and Evaporation minus Precipitation (E–P) sources. Evaluating these terms along the contour and dividing by the local gradient of CWV provides a physically interpretable basis for diagnosing where and why a lake expands, contracts, or moves. The moisture budget framework explains why vapor lakes exhibit slow westward drift, deformation, and occasional merging or splitting events. Boundary evolution is dynamically controlled, with both horizontal and vertical moisture advection contributing systematically to the lake motion and deformation. E–P sources play a secondary role in imparting boundary displacement, but act as the dominant moisture sink within the lake interior, balancing sustained precipitation. These diagnostics show how delicate moisture-dynamical adjustments along the margin counter rainout and support longevity.
Apr 17: STUDENT SEMINARS
Rachel Sampson (MPO)
Michael Perez (ATM)
Characterizing Thin Super-Cooled Liquid Water Clouds
Using Airborne Microwave Radiometry during ARCSIX
The Arctic is warming four times more rapidly than the rest of the world, most dramatically evident through the loss of sea ice. Increased Arctic moisture, in the form of water vapor and low-lying clouds, can further the surface warming of sea ice towards the melting point. The optically thin clouds with the largest warming impact are difficult to distinguish from the bright sea ice, challenging satellite cloud characterization. To address this, the NASA Arctic Radiation-Cloud-Aerosol-Surface Interaction Experiment (ARCSIX) campaign deployed an upward-pointing G-Band Vapor Radiometer (GVR) capable of discriminating super-cooled water from ice against the cold background of space. The GVR's four bands centered at 183 GHz have strong sensitivity to small changes in water vapor and liquid water paths (WVP, LWP) but the nonlinear response challenges retrievals based on linear relationships. An optimal estimation framework is developed from radiative transfer simulations applied to dropsonde thermodynamic profiles released during the campaign. The June 7, 2024, flight sampled a low-level single-layer cloud of super-cooled water and is therefore a perfect test case for the retrieval. Retrieved LWPs varied from 10 to 50 g/m2 on a length scale of ~10km, with a mean bias of –9.1 g/m2 compared to the in-situ measurements. These LWP values are well within the range to radiatively aid in surface warming. The June 7 clouds are typical of the clouds sampled during ARCSIX: ~98% of clouds sampled during the onset of the sea ice melt season were of a similar LWP, indicating their critical role in surface heating.
Dailen Jeng (OCE)
Using Compound-Specific Isotope Analysis of Amino Acids
to Examine Seasonal and Size Fraction Differences in Marine Particulate Organic Matter
In recent years, the use of compound-specific isotope analysis (CSIA) has increased. This powerful technique allows for the simultaneous measurement of source nitrogen isotopic composition (δ15N) and the calculation of the trophic position of organic material. In addition, the δ15N value of the amino acid threonine distinguishes between the biomass of microbial heterotrophs and the waste products (feces) of metazoan heterotrophs. In this study, we use CSIA of amino acids and bulk δ15N measurements to elucidate differences in size-fractionated marine particulate organic matter (POM) under contrasting seasonal conditions at the Bermuda Atlantic Time-series Study site, a location within an oligotrophic gyre characterized by deep winter mixing and strong summer stratification. We find that large nitrogen-rich zooplankton fecal pellets are produced in the upper ocean during deep winter mixing conditions. Additionally, we find that large particles have distinct isotopic signatures compared to small and submicron particles, potentially driven by higher trophic-level material present in the large particle size fraction.
Apr 17 (3:00 pm, MSC 343): Marcus van Lier-Walqui
NASA Goddard Institute for Space Studies / Columbia University, New York
Guest of Milan Curcic, Department of Ocean Sciences
Progress on the Next Generation of Earth System Modeling at NASA GISS:
Calibrated Physics Ensembles, New Cloud Parameterizations, and
Methods for Quantifying the Value of Observations
New York City's NASA Goddard Institute for Space Studies develops and maintains the ModelE Earth system model (ESM), a global coupled (land, atmosphere, ocean) climate model that provides contributions to the Coupled Model Intercomparison Project (CMIP). We have recently implemented methods to use available sources of observational data (Earth-observing satellites, field campaigns, etc.) to calibrate uncertain model parameters, and quantify uncertainty in model predictions, in order to best inform projections of global climate impacts. I describe our use of machine learning and Bayesian parameter estimation to create what we call a "calibrated physics ensemble". I'll also present a concept to use this parameter calibration methodology to evaluate the information content of proposed observations (such as a future NASA satellite mission), akin to an Observing System Simulation Experiment (OSSE). I'll discuss the importance of observational uncertainty quantification for these efforts, and point out where existing observational uncertainty estimates are insufficient. Finally, I will present ongoing efforts to create next-generation parameterizations for ESMs, using both traditional physically-based, as well as data-driven, approaches. I will stress that our approach is to develop physical models of atmospheric processes, as opposed to purely data-driven "black-box" approaches, but offer perspectives on where machine learning gives key advantages. I will also discuss changes to Earth system modeling at NASA, and give some hint as to our future directions.
Apr 24: STUDENT SEMINARS
Josiah Kaiser (ATM)
Sabrina Glynn (OCE)
Madeleine Dawson (OCE)
