FALL 2023
Wednesdays at 3:00 pm, Seminar Room SLAB 103 / Virtual SLAB 103
Aug 23: NO SEMINAR
Aug 30: NO SEMINAR
Sep 06: NO SEMINAR
Sep 13: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. Brian Mapes
Department of Atmospheric Sciences, Rosenstiel School
How Can We Understand the Organization of Atmospheric Convection?
Recording Available at COMPASS ON DEMAND
Two questions follow the title: What is organization? and: What is understanding? These define a philosophical pursuit that has been the through-line, and the curiosity-juice, of my scientific life. The associated funding has been justified by both human impacts and numerical model engineering (parameterization): Organization matters. The first question can be answered as a definition: Organization is non-random structure, with a purpose. But now we have a third question: What is purpose? More on that below.
Atmospheric convection (viewed in its broadest sense) is the most dynamic process in the Earth system, short of biological life, which physical scientists unanimously agree is too darn complicated. Convection exhibits (as bright visible clouds, inspiringly!) structure on scales from landscape to planetary. Mere 3D description can fill volumes – but is not understanding. These structures change from minutes to millennia, but again a description is not understanding. All of it obeys what we can consider known differential equations, but even that deep truth falls short of understanding.
I will argue that the conceptual basis for what deserves the name 'understanding' is evolutionary reasoning. Familiar from bio & eco/econ sciences, but with key application-dependent differences, this way of thinking connects the principle of time to its logical predictions of what one should expect to find in a very old world. Those predictions can be shaped into falsifiable tests of theory, and into practical implications to motivate the effort. This theory is where purpose must come in, and the different specificity and timescales of memory of systems (mere inertia, not neurons or DNA). All in the context of a flow of energy through different possible configurations of matter, whose complexity and thus unlikeliness can be measured by entropy (but in the information sense, free of the ghost of the Second Law of Thermodynamics). It's not familiar stuff, students, but I will try to explain or at least give a glimpse worth your hour.
Sep 20: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. Lisa Beal
Department of Ocean Sciences, Rosenstiel School
Introducing the Beal Lab
Recording Available at COMPASS ON DEMAND
In this special faculty presentation I will give an overview of the work of the Ocean Sciences Beal Lab. Our research focuses on understanding western boundary currents and their role in oceanic and climate change. These currents – like the Gulf Stream and the Agulhas Current in the southern hemisphere – carry enormous amounts of momentum, heat, salt, and nutrients away from the tropics and towards subpolar latitudes, where they can fuel the mid-latitude storm-tracks, promote central and deep water formation, and drive primary production. Along the way, instabilities in western boundary currents drive upwelling events over the continental margin, causing extreme variability in shelf-sea temperatures and biomass.
We observe these current systems with in situ instrumentation, including CTDs, ADCPs, current meters, inverted echo-sounders, thermistors, drifters, profiling floats, and more recently, oxygen, nitrate, pH, and pCO2 sensors. Often we deploy instrumentation on subsurface moorings and leave them for a year or two so we can quantify the variability of the current and its fluxes. We also use satellite data, Global Ocean Observing System data, and simulations to add greater context to our measurements.
I will wrap up my presentation with a brief overview of three ocean-going projects that the Beal Lab is currently conducting in collaboration with other groups. The projects address pressing questions about western boundary currents in a time of accelerating climate change, including: How does the Gulf Stream influence sea level and coastal flooding in South Florida? How do changes in the Gulf Stream affect downstream biomass and anthropogenic carbon drawdown? Is the leakage of warm and salty Agulhas waters into the South Atlantic really increasing and what proportion is carried outside Agulhas rings?
Sep 27: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. Paquita Zuidema
Department of Atmospheric Sciences, Rosenstiel School
A Recent Research Overview With a Focus on Mixed-Phase Clouds
Most of the research pursued by myself and student / postdoc colleagues at Rosenstiel has examined processes affecting the lifecycle and radiative impact of marine low clouds. This is ultimately motivated by the clouds' relevance to climate. One research focus is on the southeast Atlantic basin, where our combined efforts are generating a holistic view of the coupling of the basin's marine stratocumulus deck to land, ocean, and atmospheric processes, currently led by Tyler Tatro. Another, more recent focus is the cold-air outbreaks off of the eastern US seaboard, such as partially seen in the aftermath of Hurricane Idalia. Cold-air outbreaks provide dramatic visual examples of cloud transitions from overcast stratocumulus to more broken cloud fields. At higher latitudes, these clouds are typically mixed-phase (a combination of liquid and ice). Climate scientists care about the ice / liquid phase partitioning and respective optical depth feedbacks on the global energy balance. The mixed-phase clouds, despite remaining shallow because of mesoscale subsidence, are just as impactful for weather. High-latitude cold-air outbreaks are often precursors to polar lows, the Arctic equivalent of hurricanes. Polar lows notwithstanding, the warming Arctic is highlighting the need for improved location-specific weather prediction for coastal communities and shipping. Assistant Scientist Seethala Chellappan and myself are examining the context of five cold-air outbreaks sampled during a NASA aircraft campaign held in 2020-2022 offshore of Virginia. Our goal is to better understand the underlying processes affecting the Lagrangian (=cloud-following) cloud evolution. A further motive is to prepare myself and Samual Ephrain for upcoming field work in 2024 examining winter cold-air outbreaks over the Norwegian Sea using NSF research aircraft, and myself and Michael Perez, for examining summer Arctic mixed-phase clouds north of Greenland from NASA aircraft. In addition to our leadership, we are contributing observationally through an airborne passive microwave instrument responsive to only the liquid but not the ice in mixed-phase clouds. We will use the measurements to inform process depictions of Lagrangian cloud evolution, many of which are highly dependent on cloud liquid water path as well as cloud top temperature for mixed-phase clouds. This presentation will give an overview of the scientific 'evolution' of this overall research focus.
Oct 04: Dr. Emily Becker
Cooperative Institute for Marine and Atmospheric Studies, Rosenstiel School
Oct 11: Dr. Ved Chirayath
Aircraft Center for Earth Studies / Department of Ocean Sciences, Rosenstiel School
Flying Boats and Drones That See Through Waves –
Highlights From the Aircraft Center for Earth Studies
Oct 18: Dr. Rachel Gaal
Department of Atmospheric Sciences, Rosenstiel School
Oct 25: Dr. Chengfei He
Department of Atmospheric Sciences, Rosenstiel School
Recent Tropical Atlantic Multidecadal Variability is Dominated by External Forcing – A Story of Love and Family Search
The tropical Atlantic climate is characterized by prominent and correlated multidecadal variability in Atlantic sea surface temperatures (SSTs), Sahel rainfall and hurricane activity. Owing to uncertainties in both the models and the observations, the origin of the physical relationships among these systems has remained controversial. Here we show that the cross-equatorial gradient in tropical Atlantic SSTs – largely driven by radiative perturbations associated with anthropogenic emissions and volcanic aerosols since 1950 – is a key determinant of Atlantic hurricane formation and Sahel rainfall. The relationship is obscured in a large ensemble of CMIP6 Earth system models, because the models overestimate long-term trends for warming in the Northern Hemisphere relative to the Southern Hemisphere from around 1950 as well as associated changes in atmospheric circulation and rainfall. When the overestimated trends are removed, correlations between SSTs and Atlantic hurricane formation and Sahel rainfall emerge as a response to radiative forcing, especially since 1950 when anthropogenic aerosol forcing has been high. Our findings establish that the tropical Atlantic SST gradient is a stronger determinant of tropical impacts than SSTs across the entire North Atlantic, because the gradient is more physically connected to tropical impacts via local atmospheric circulations. Our findings highlight that Atlantic hurricane activity and Sahel rainfall variations can be predicted from radiative forcing driven by anthropogenic emissions and volcanism, but firmer predictions are limited by the signal-to-noise paradox and uncertainty in future climate forcings.
Nov 01: Drs. Tero Mielonen & Kanika Taneja
Invited Speakers of the Department of Atmospheric Sciences
Finnish Meteorological Institute, Kuopio, Finland
Nov 08: Yueyang Lu
Department of Ocean Sciences, Rosenstiel School
(one-hour MPO student seminar)
Nov 15: (AVAILABLE)
Nov 22: NO SEMINAR (Thanksgiving Recess)
Nov 29: Dr. Sujan Shrestha
Department of Atmospheric Sciences, Rosenstiel School
SPRING 2024 PREVIEW:
Jan 24: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. Sharan Majumdar
with contributions from coworkers
Department of Atmospheric Sciences, Rosenstiel School
Jan 31: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. Amy Clement
Department of Atmospheric Sciences, Rosenstiel School
