FALL 2023
Wednesdays at 3:00 pm, Seminar Room SLAB 103 / Virtual SLAB 103
(unless stated otherwise)
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
Recording Available at COMPASS ON DEMAND
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 (CIMAS), Rosenstiel School
The Path to Climate Prediction
Recording Available at COMPASS ON DEMAND
This talk will describe my research in climate prediction, from basic science, development of prediction applications, and communication with user communities. Research includes the predictability of anomalies and extremes, diagnostics of El Nino / Southern Oscillation (ENSO) teleconnection effects on the characteristics of daily precipitation and temperature, and initialized climate prediction ensemble models. I will describe my experience with the operational and research components of The North American Multi-Model Ensemble (NMME), a UM-led research / realtime prediction system and a powerful vehicle for improving seasonal climate prediction. Emerging projects include investigations into ENSO's impacts in a future climate, research to inform decadal projections, and NMME predictions of the seasonal risk of coastal flooding. Climate predictions are only useful if users can understand them, and woven throughout my work is a focus on communication as the lead writer for NOAA's climate.gov ENSO Blog.
Oct 11: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
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 (ACES)
Recording Available at COMPASS ON DEMAND
We have mapped more of the surface of the Moon and Mars than our own ocean floor – but that is changing. Professor Ved Chirayath will present three remote sensing technologies he invented during his time at NASA and continues to develop for the agency at Rosenstiel's ACES. These technologies will help us better understand Earth’s marine environments while furthering the search for life on other planets. New developments will be shared on the first flying electric research vessel, a next-generation zero emission research platform for coral mapping, automated drone missions, and marine plastic detection. In addition, new advances from missions surveying coral reefs in Florida as well as imaging cetaceans will be presented from 2023 field missions.
Advances in active MiDAR remote sensing technology, fluid lensing, and NeMO-Net will be shared in the context of seven newly-funded proposals. Several new PhD assistantships in ACES will be advertised in addition to two new staff positions. Finally, a new ACES lab and field course is being offered in Spring 2024, based on a newly authored textbook, MSC332 - Planetary Science, the Search for Life, & Oceans Across the Solar System.
Ved Chirayath is a National Geographic Explorer and the Vetlesen Professor of Earth Studies, Mechanical, & Aerospace Engineering at the University of Miami’s Aircraft Center for Earth Studies.
Oct 18: Dr. Rachel Gaal
Department of Atmospheric Sciences, Rosenstiel School
The Role of Soil Moisture State on the Incidence of
Summer Mesoscale Convective Systems in the U.S. Great Plains
Recording Available at COMPASS ON DEMAND
This talk will be focused on my dissertation research, which was motivated by recent literature that showed summer mesoscale convective systems (MCS) in the U.S. Great Plains can often occur in weakly-forced synoptic environments (although MCS are classically known to develop in strongly-forced synoptic environments). Considering the framework of local Land-Atmosphere (L-A) coupling, it is natural to wonder if convection in these weakly-forced environments may be triggered by anomalous soil moisture (SM) conditions. Using an MCS database covering the contiguous U.S. east of the Rocky Mountains in boreal summers 2004-17, my work aimed to explore this question by identifying the SM conditions associated with weakly-forced summertime MCS initiations in the U.S. Great Plains, and to also look through the lens of local L-A coupling to identify a mechanism of interaction between the SM state and MCS initiations using convective-permitting simulations with the Weather Research and Forecasting model. In this presentation, I will highlight the main findings of my work which suggests that organized SM heterogeneity [O(100)km] aligned with the mean low-level wind field can influence the location of MCS initiations, such that events are preferred upstream of the mean wind over the drier patches of SM. This main finding is similar to previous results in the Sahel which suggest induced meso-β circulations related to near-surface thermodynamic variable fluctuations can drive MCS initiations.
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
Recording Available at COMPASS ON DEMAND
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: Invited Speakers of the Department of Atmospheric Sciences
Dr. Tero Mielonen
Finnish Meteorological Institute, Kuopio, Finland
From Aerosols to Clouds: A Brief Overview of Atmospheric Science
Done at The Research Centre of Eastern Finland (FMI)
Recording Available at COMPASS ON DEMAND
The Research Centre of Eastern Finland is part of the Finnish Meteorological Institute. It is located in Kuopio, Finland. The Centre's research focuses on the interactions between aerosol, cloud, precipitation, and climate. To obtain a holistic understanding of these interactions, the research is done in three groups: Atmospheric Measurements, Atmospheric Modelling, and Atmospheric Radiation. In this presentation, I will give some examples of our research topics, highlighting our work related to biogenic aerosols and wildfire smoke, and their impacts on cloud properties. These aerosols can have significant climate and health impacts, and their relevance will increase in the future as anthropogenic emissions are reduced.
Dr. Kanika Taneja
Finnish Meteorological Institute, Kuopio, Finland
Investigating the Impact of Atmospheric Aerosols on Low-Level Warm Clouds
Recording Available at COMPASS ON DEMAND
One of the largest uncertainties in estimating the anthropogenic radiative forcing is related to the impact of atmospheric aerosols on cloud properties. This uncertainty originates mainly from the complicated nature of aerosol-cloud interaction as it is much stronger and more difficult to observe than the aerosol-radiation interaction. The estimates of radiative forcing due to changes in cloud properties vary significantly between different global climate models, highlighting the need for constraining this forcing by using observations. In this study, we aim to quantify the radiative effects of biogenic secondary organic aerosols (BSOA) by combining field observations of aerosol properties and satellite observations of cloud properties together with large eddy simulations, and meteorological reanalysis data. The level-2 collection-6 MODIS cloud property dataset with 1 km resolution is used, and cloud droplet number concentration (CDNC) values are calculated for liquid, single-layer clouds. The particle number concentration data is taken from in-situ observations and only particles with diameter larger than 100 nm (N100) are considered in this study as they are large enough to act as cloud condensation nuclei (CCN). These two datasets are collocated with each other, and the relationship between CDNC and N100 is assessed over two different regions, the Southern Great Plains (U.S.) and Hyytiälä (Finland). In this context, we also show how the defined relationship between aerosols and cloud properties depends on the consideration of measurement errors and linear regression methods. The results obtained from the observations are also compared with the theoretical relationships obtained from the large eddy simulations (UCLALES-SALSA).
Nov 08: NO SEMINAR
Nov 15: NO SEMINAR
Nov 22: NO SEMINAR (Thanksgiving Recess)
Nov 29: Dr. Sujan Shrestha
Department of Atmospheric Sciences, Rosenstiel School
Insights Into Urban Air Quality:
From Biomass Burning Plumes to Ozone Formation in Texas
Recording Available at COMPASS ON DEMAND
As criteria pollutants from anthropogenic emissions have declined in the US in the last two decades, biomass burning emissions are becoming more important for urban air quality. Biomass burning activities emit fine particulate matter (PM2.5), volatile organic compounds (VOCs), and trace gases into the atmosphere. The biomass burning plumes can be transported across long distances and impact air quality in downwind locations. During long-range transport, the physical properties and chemical composition of the plume can be altered significantly by both plume aging and dilution due to boundary layer mixing. In urban locations that are burdened by local anthropogenic sources, it is challenging to characterize and quantify the impacts of aged and / or dilute biomass burning smoke plumes. In this presentation, I will delve into various approaches, including ground-based and satellite observations of aerosol composition and optical properties, to investigate the physical and chemical characteristics of transported biomass burning smoke and its effects on background air quality. Focusing on Port Aransas, an industrialized coastal site in Texas, I will discuss the methods employed and key findings.
Further, in the context of growing urban areas with changing emission landscapes and increasing populations, a comprehensive understanding of factors influencing air quality is crucial. Notably, the Texas cities including Houston and San Antonio have been designated as non-attainment for the National Ambient Air Quality Standards (NAAQS) for ozone (O3) pollution by the US EPA. This non-attainment designation demonstrates the impact of urbanization and industrialization on the air quality in these cities. The production of tropospheric O3 can be either nitrogen oxide (NOx)-limited or VOC-limited, and understanding the sources of both precursors is relevant for characterizing urban O3 production. I will present a comprehensive analysis of VOC and trace gas concentrations, trends, emission ratios, and sources in these urban centers. By incorporating field measurements of VOCs and trace gases, I will discuss the O3 formation regime in these cities in Texas. The investigation of the O3 formation regime is important to determine the effectiveness of O3 control policies.
These studies were conducted during multi-institute field campaigns including TRacking Aerosol Convection interactions ExpeRiment – Air Quality (TRACER-AQ) and Corpus Christi and San Antonio (CCSA) Field Study.
Dec 04 (Monday): Dr. Christopher Holmes
Invited Speaker of the Department of Atmospheric Sciences
Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee
Impacts of Fires on Air Quality in the Eastern United States
Fires are widespread and frequent across the eastern United States, as they are used extensively for wildfire mitigation, ecosystem management, and disposing of biomass debris from agriculture and land clearing. Historically, the extent of these fires has been underestimated due to the lack of comprehensive burn records and the difficulty of detecting small, short-duration fires from satellites. We use the improved fire detections from the Advanced Baseline Imager (ABI) on GOES-16 and a new compilation of locally specific emission factors to develop a new biomass burning inventory for the eastern U.S. Using the GEOS-Chem atmospheric chemistry model, we evaluate the emissions against constraints from observations of surface PM2.5, aerosol optical depth (AOD), and FIREX-AQ. The new inventory fits these observations as well or better than multiple other emission inventories and suggests that fire emissions are likely at the upper end of the wide range of previous estimates. We quantify the impacts on air quality in the eastern U.S. and discuss the implications for prescribed fire management.
Dec 06 (Auditorium): Yueyang Lu
Department of Ocean Sciences, Rosenstiel School
(one-hour MPO student seminar)
On the Mesoscale Eddy Effects on Oceanic Tracers:
Dispersion, Frontogenesis, and Parameterization
Recording Available at COMPASS ON DEMAND
Mesoscale eddies on length scales of O(10-100) km are ubiquitous in the ocean. They profoundly affect the distribution of tracers such as carbon and nutrients. The eddies can enhance mixing of the tracers, disperse tracer anomalies, and generate tracer fronts. Mesoscale eddies are partially resolved in ocean climate models, and their effects on tracers must be parameterized. Extant parameterization uses eddy-induced advection and diffusion to represent eddy fluxes of the tracers. However, this framework is still insufficient to fully account for the eddy effects.
In this talk, I will introduce a novel approach of using a combination of eddy-induced generalized advection and diffusion for representing the eddy-induced stirring, dispersion, and frontogenesis in models that do not resolve the oceanic mesoscale. Using a high-resolution model of the Gulf Stream region, I will show that the new framework outperforms the diffusion-based parameterization of eddy fluxes in reproducing the eddy-induced stirring and dispersion in a simulation without mesoscale currents. I will then discuss the role of eddies in sharpening oceanic fronts such as a front associated with the Gulf Stream. An analysis of the frontogenesis equation demonstrates that the eddies sharpen the front whereas the large-scale current weakens it. The eddy-induced frontogenesis can be readily reproduced by the novel advection-based approach in a low-resolution model, whereas the diffusion-based parameterizations fail to produce the front. A closure for the approach will also be discussed. These studies demonstrate advantages of using an advective framework for representing important eddy effects in ocean climate models.
