FALL 2026
Fridays at 11:00 am, Rosenstiel School Auditorium / Virtual Auditorium
Aug 21: NO SEMINAR
Aug 28: NO SEMINAR
Sep 04: NO SEMINAR
Sep 11: NO SEMINAR
Sep 18: NO SEMINAR
Sep 25: Drs. Dan Collins and Emerson LaJoie
NOAA / NWS / NCEP Climate Prediction Center, Riverdale Park, MD
Guests of Marybeth Arcodia, Department of Atmospheric Sciences
Accessing Sources of Predictability for
Subseasonal-to-Seasonal (S2S) Climate Prediction
Recording Available at COMPASS ON DEMAND
Predictability of climate on S2S timescales emerges in dynamical models from fundamental physical principles on the grid scale to the extent that they describe large-scale sources of predictability. For example, climate phenomena such as the El Nino Southern Oscillation (ENSO) and Madden Julian Oscillation (MJO) are known sources of predictability at this timescale. However, dynamical models are imperfect in their description of the climate system, limiting their prediction skill, relative to theoretical predictability limits. Statistical methods have long been applied to both optimize the extraction of information from dynamical model forecasts, and to make statistical predictions from relationships between current and future states of the climate system, without explicitly describing physics. While artificial intelligence (AI) systems are being developed to extend these concepts, extracting potentially nonlinear information from large multivariate datasets, currently applied forecast tools generally use linear statistical methods and are limited in their consideration of state-dependent predictability, i.e. forecasts of opportunity. This talk describes some of the methods currently employed by the National Weather Service / Climate Prediction Center to access predictability from statistical and dynamical models, as well as methods to combine or consolidate models. The skill and limitations of these forecast systems, as well as the potential for development of new forecast tools, will be discussed.
Oct 02: NO SEMINAR
Oct 09: NO SEMINAR (Rosenstiel School faculty meeting)
Oct 16: Student Seminars
Christina Schuler (ATM)
Coupled Variability in the Gulf Stream-NASH System
in a High-Resolution Coupled Model
The intensity and position of the North Atlantic Subtropical High (NASH) and the Gulf Stream play prominent roles in determining the trajectory of North Atlantic tropical cyclones (TCs). However, the impact of the Gulf Stream on NASH variability and consequent feedback mechanisms is less understood. This research analyzes the coupled dynamics between the Gulf Stream and the subtropical high by incorporating 850-hPa geopotential height, sea surface temperature (SST), and zonal and meridional ocean current velocities. Maximum covariance analysis (MCA) is employed to identify dominant modes of ocean–atmosphere variability among these fields. Regression analyses paired with statistical significance testing provide confidence whether there is a physical connection between oceanic and atmospheric variables. The results suggest that a stronger subtropical gyre (with an amplified western boundary current) leads to an enhanced meridional SST dipole (warm north and cold south) in the North Atlantic and intensified northward heat transport. Moreover, there is statistical significance for both SST and 850-hPa regression analyses from the model dataset. However, that significance lessens or is not present from the observational estimates due to the signal-to-noise ratio decreasing for smaller sample sizes. We additionally hypothesize that an increase in northward heat transport reinforces the NASH, amplifying the likelihood for straight-moving cyclones. Future research using modeling experiments will test this potential positive feedback mechanism.
Michael Perez (ATM)
Characterizing Thin Super-Cooled Liquid Water Clouds
Using Airborne Microwave Radiometry During ARCSIX
The Arctic is warming at a faster rate than anywhere else on the planet, most dramatically evident through the loss of sea ice. Increased Arctic moisture 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 from space, challenging satellite cloud characterization. To address this challenge, 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 4 bands centered at 183 GHz have strong sensitivity to small changes in water vapor and liquid water paths (WVP, LWP). An optimal estimation retrieval is developed from radiative transfer simulations applied to dropsonde profiles released during the campaign. So-named "cloud walls" provide multiple repeat measurements of cloud decks, with which we compared GVR-retrieved LWPs to in-situ measurements collected during profiles through the cloud. The cloud wall executed on June 7, 2024, sampled a low-level single-layer cloud of supercooled water, a perfect test case for the retrieval. Retrieved LWPs varied from 10 to 50 g/m2 with a mean bias of –9.1 g/m2 compared to the in-situ measurements, but otherwise they were in good agreement both in scale and variability. Radiative analyses show a mean net cloud radiative effect of ~33 W/m2. Approximately 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.
Oct 23: Student Seminars CALENDAR LINK
Abigail McDonnell (ATM)
How Individual Climate Forcings Alter Radiative Forcing From CO2
Radiative forcing from CO2 is a fundamental metric for estimating climate sensitivity. Recent work has shown that this value, which had been previously assumed to be constant, actually depends on the climatological base state and increases as the stratosphere cools and the troposphere warms. As a result, the climate's response to CO2 amplifies the radiative forcing caused by future increases in CO2. Many forcing agents other than CO2 alter the climatological base state, which may modify the radiative forcing from CO2, but their individual contributions have not been isolated. Here, we quantify how individual historical forcings have changed the instantaneous radiative forcing from a doubling of CO2 (IRF2×CO2) through their effect on the climatological base state. We use historical and single-forcing simulations from four CMIP6 models in the Large Ensemble Single Forcing Model Intercomparison Project (LESFMIP), and compute IRF2×CO2 offline with SOCRATES radiative transfer code. We find that IRF2×CO2 increased by about 0.16 W m−2 (6.7%) between 1850-1900 and 1985-2014, with approximately 85% of that increase arising from changes in the stratosphere. Individually, well-mixed greenhouse gases raise IRF2×CO2 by 6.5%, ozone changes add 1.5%, and anthropogenic aerosols lower it by 1.2%. The forcing from CO2 therefore also depends on the evolution of non-CO2 forcings, which is important to consider when estimating climate sensitivity.
Samuel Ephraim (MPO)
Towards Developing a Modeling Framework to Investigate the Drivers of a
Closed-to-Open Cell Mixed-Phase Cloud Transition Observed Over the Nordic Seas
Closed-to-open cell transitions in mixed-phase clouds during marine cold air outbreaks strongly influence high-latitude climate, yet models struggle to represent the dynamic, thermodynamic, microphysical processes and aerosol-cloud interactions that inform the transition. Previous studies have shown that surface fluxes and free-tropospheric conditions affect these transitions but have often lacked data to quantify the internal contribution of precipitation. During the Cold-Air outbreak Experiment in the Sub-Arctic Region campaign, a closed-to-open cell transition was observed under cold, polluted conditions in the presence of strong surface fluxes. Observed ice particle number concentrations suggest that secondary ice production (SIP) was active at temperatures too cold for Hallett-Mossop rime splintering, the only SIP mechanism represented in most models. Additional SIP mechanisms, such as ice-on-ice collisional breakup and freezing-induced drop fragmentation, appear necessary to explain observed ice particle number concentrations. Upstream of the transition, decreasing cloud condensation nuclei concentrations allowed supercooled droplets to grow larger, increasing riming efficiency. Open cells contained intense precipitation shafts with cold pools reaching the ocean surface. Motivated by this case, we present a framework using large-domain large-eddy simulations in WRF to examine how a weakening inversion, precipitation-driven cold pools, or both, in the presence of strong surface fluxes, help drive the transition. Sensitivity experiments will examine how aerosol-cloud interactions and SIP influence the development of frozen precipitation, while experiments with sublimational cooling disabled will isolate the contribution of cold pools. These results will inform future model development.
Shanna Chamhitt (ATM)
Investigating Non-Propagating Waves in the Outflow Layer of Tropical Cyclones
Using Geostationary Satellite Data
Increasing attention has been directed toward the upper outflow layer of tropical cyclones (TC), where key dynamical processes remain poorly observed. Wave activity in this region is thought to be influenced by internal storm dynamics as well as the surrounding environment, and may provide insight into storm intensity, suggesting the need to better understand wave behavior in the outflow region. Nolan and Onderlinde [2022] investigated spiral gravity waves in the TC outflow, and discovered another distinct wave pattern – non-propagating waves (NPWs). This study focuses on NPWs, which we define as features that resemble spiral gravity waves but lack their rapid outward propagating motion. We investigate whether NPWs can be quantitatively identified using geostationary satellite data, while noting the environmental conditions and patterns in which they usually develop. Visible imagery from West Pacific and North Atlantic TCs (2014-2024) was manually inspected, revealing NPWs in most major category storms, particularly during periods of intensification and low wind shear. Linear and azimuthal profiles of normalized radiance values are extracted to distinguish outward-propagating gravity waves from NPWs. Peaks in the radiance profiles, interpreted as individual waves, are identified and tracked to estimate propagation and tangential speeds. The analyses reveal NPWs to exhibit spatial and temporal continuity, supporting their identification as coherent wave-like features. This study represents an initial step toward understanding NPWs, laying the groundwork for future efforts to objectively track and analyze their behavior in the TC outflow.
Oct 30: G. Rees1, Dr. J. Olascoaga2, Dr. Y. Wang3, Dr. B. Dano4 CALENDAR LINK
1Altametry Inc., Miami
2Department of Ocean Sciences, Rosenstiel School, UM
3Department of Chemical, Environmental and Materials Engineering, College of Engineering, UM
4Department of Mechanical and Aerospace Engineering, College of Engineering, UM
Guests of Siyuan Wang, Department of Atmospheric Sciences
Persistent Low-Altitude Observation With a Tethered Balloon System:
From Sargassum to Smoke to Sharks
Many environmental processes evolve over hours to days and at scales of meters to kilometers: sargassum mats that deform and beach, smoke plumes whose concentrations change with height, wildlife that appears near shore for only minutes at a time. A process cannot be fully understood from a snapshot, yet optical satellites either pass over briefly or observe continuously only at coarse resolution, and cannot see through cloud; aircraft and drones resolve detail but only for short periods; and fixed sensors measure one place at one height. Despite advances in each, continuous, high-resolution observation at this intermediate scale remains largely unavailable, limiting how well these processes can be studied, tested against models, and predicted.
In this seminar, three speakers show that persistent, low-altitude observation from one platform, a relocatable tethered balloon system operated by Altametry from land or sea, can address that gap across three different settings. Dr. Josefina Olascoaga (Rosenstiel School) will present results from a July 2026 Biscayne Bay deployment, in which continuous overhead imagery of sargassum mat deformation was paired with a new drifter carrying an optical sensor and accelerometer to test whether drifters stay embedded in the same mat and to quantify waves' contribution to the mat motion. Dr. Yang Wang (College of Engineering) will describe January 2024 pilot measurements over the University of Miami campus that revealed strong vertical variability in PM2.5, and how they led to a proposed approach for measuring prescribed-fire smoke fluxes. Dr. Bertrand Dano (College of Engineering) will present 2017-2020 work with the Atlantic White Shark Conservancy and the Massachusetts Division of Marine Fisheries off Cape Cod, using continuous aerial imagery and AI-assisted methods toward a prototype early shark-detection system. A live demonstration of the tethered balloon system follows the seminar, so attendees can discuss how it might serve their own research.
Gary Rees, Director of Research at Altametry Inc., leads research and academic partnerships at Altametry, which develops and operates tethered balloon systems for persistent low-altitude observation. Before joining Altametry, he spent 42 years in the intelligence community, including service in Naval Intelligence, the CIA, and six years at the National Reconnaissance Office, where he worked on the nation's reconnaissance satellites. He is a University of Miami alumnus (Class of 1979).
Dr. Maria Josefina Olascoaga, Professor in the Department of Ocean Sciences of the Rosenstiel School, holds an ScD in physical oceanography from CICESE (Mexico). Her research applies nonlinear dynamical systems theory, including Lagrangian coherent structures, to understand how ocean currents transport biogeochemical material. Applications include forecasting Deepwater Horizon oil slick instabilities, larval connectivity in the Gulf of Mexico, and the drift of Sargassum, including a 2024 PNAS Nexus paper with F J. Beron-Vera and G. Bonner extending the Maxey-Riley model to Sargassum.
Dr. Yang Wang, Associate Professor in the Department of Chemical, Environmental and Materials Engineering of the University of Miami's College of Engineering, is an aerosol scientist whose research addresses aerosol particle formation in engineering and atmospheric systems, aerosol and air quality, aerosol-cloud interactions, and the health effects of airborne particles. He earned his PhD at Washington University in St. Louis (2017), held a postdoctoral position at Brookhaven National Laboratory, and served on the faculty of Missouri S&T before joining the University of Miami in 2022. He has authored or co-authored more than 70 peer-reviewed publications and received the 2025 National Science Foundation CAREER Award.
Dr. Bertrand Dano, Assistant Professor of Professional Practice in the Department of Mechanical and Aerospace Engineering of the University of Miami's College of Engineering, is an aerospace engineer. His published work includes computational and performance studies of coflow jet airfoils, in collaboration with Dr. Ge-Cheng Zha. Between 2017 and 2020 he worked with the Atlantic White Shark Conservancy and the Massachusetts Division of Marine Fisheries on aerial observation of sharks and seals off Cape Cod, using a tethered balloon platform and AI-assisted detection methods.
Nov 06: NO SEMINAR (SUSTAIN event in Auditorium)
Nov 13: Katrina Simi CALENDAR LINK
Department of Ocean Sciences, Rosenstiel School
(1-hour OCE student seminar)
Nov 20: Victoria Pizzini CALENDAR LINK
Department of Ocean Sciences, Rosenstiel School
(1-hour ATM student seminar)
Nov 27: NO SEMINAR (Thanksgiving Recess)
Dec 04: Snigdha Samantaray CALENDAR LINK
Department of Atmospheric Sciences, Rosenstiel School
(1-hour MPO student seminar)
Feb 12: NO SEMINAR (Parents Council in Auditorium)
Feb 26: Reserved for three visitors of Mariana Bernardi Bif
