COMPASS Wednesday - Archive

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COMPASS Wednesday

Combined OCE MPO ATM Seminar Series

Wednesdays at 3:00 pm, Seminar Room SLAB 103 / Virtual SLAB 103
(unless stated otherwise)





Feb 15 (Tuesday, 9:30 am): Dr. Shane Murphy
Faculty Candidate for the Center for Aerosol Science and Technology, University of Miami
College of Engineering and Applied Science, University of Wyoming, Laramie

Improving Our Understanding of Two Critical Short-Lived Climate Forcers:
Absorbing Aerosol and Methane

After carbon dioxide, emissions of absorbing aerosol and methane represent two of the largest anthropogenic forcers of global climate change. The optical properties of absorbing aerosols (primarily soot, brown carbon, and dust), remain poorly constrained and parametrized. In this seminar, I will present some of my group's recent fieldwork that has improved our understanding of the optical properties of absorbing aerosol emitted by wildfires and discuss integration of this observational knowledge into global climate and chemical transport models. I will also present an instrument development project to commercialize a photoacoustic instrument, enabling more accurate measurements of absorbing aerosol globally. Reducing methane emissions from oil and natural gas production has become a major strategy of the U.S. and other governments to combat climate change. My group has conducted several recent campaigns in the Permian Basin of Texas (the World's largest oil and gas basin) and in other U.S. oil and gas basins. Data from these projects highlight the magnitude of methane emissions and the challenges we face in effectively reducing them. I will explore how ground-based, airborne and satellite measurements can be integrated together and how they compare to current emission inventories. Finally, I will discuss some possible paths forward in the methane leak detection world along with a brief discussion of my group's measurements of the air quality impacts of emissions from oil and gas extraction.

Shane Murphy received his B.S. from the University of Colorado in Chemical Engineering, then taught high school chemistry in the Teach for America Program before earning his Ph.D. from Caltech, where he was a NASA Earth and Space Sciences Graduate Fellow. He was a National Research Council Postdoctoral Fellow at the National Oceanic and Atmospheric Administration before joining the faculty at the University of Wyoming, where he is currently an Associate Professor in the Department of Atmospheric Science and the Director of the School of Energy Resources Center of Excellence in Air Quality. His research focuses on developing and using cutting edge instrumentation to evaluate the impact of aerosols, greenhouse gases, and trace gases on air quality and climate. Much of his research is conducted in the field from airborne and mobile platforms. He has published 43 peer-reviewed articles and both his research and his graduate students have been featured in the popular media including on Wyoming Public Radio, the PBS NewsHour, and in the 2019 documentary Ice on Fire produced and narrated by Leonardo DiCaprio. In 2019 he was invited to Uganda to be a U.S. State Department Speaker on air quality.




Mar 09: Dr. Brian Arbic
SEEDS and RSMAS / DEIC 2022 Distinguished Lecturer
Earth and Environmental Sciences, College of Literature, Science, and the Arts
University of Michigan, Ann Arbor

Frequency Dependence and Vertical Structure of Ocean Surface Kinetic Energy
From Global High-Resolution Models and Surface Drifter Observations
Recording Available at COMPASS ON DEMAND

The geographical variability, frequency content, and vertical structure of near-surface oceanic kinetic energy (KE) are important for air-sea interaction, marine ecosystems, operational oceanography, pollutant tracking, and interpreting remotely sensed velocity measurements. Here, KE in high-resolution global simulations (HYbrid Coordinate Ocean Model; HYCOM, and Massachusetts Institute of Technology general circulation model; MITgcm), at the sea surface (0 m) and 15 m, are respectively compared with KE from undrogued and drogued surface drifters. Global maps and zonal averages are computed for low-frequency (periods longer than 2 days), near-inertial, diurnal, and semi-diurnal bands. In the low-frequency band, near the equator, both models exhibit KE values that are too low relative to drifters. MITgcm near-inertial KE is too low, while HYCOM near-inertial KE lies closer to drifter KE, probably due to more frequently updated atmospheric forcing. In the semi-diurnal band, MITgcm KE is too high, while HYCOM lies closer to drifters, likely due to the inclusion of a parameterized topographic internal wave drag. We assess the KE vertical structure by considering the ratio of zonally averaged KE in 0 m / 15 m model results and undrogued/drogued drifter results. Over most latitudes and frequency bands, model ratios track the drifter ratio to within error bars. All frequency bands except the semi-diurnal band display measurable vertical structure. Latitudinal dependence in the vertical structure is greatest in the diurnal and low-frequency bands. As in a previous comparison of HYCOM and MITgcm to current meter observations, HYCOM generally displays larger spatial correlations with the drifter observations than MITgcm does.

The work above was done in concert with Shane Elipot of RSMAS. I will also briefly show some preliminary results from an analysis of a new high-resolution coupled GEOS atmosphere / MITgcm ocean simulation, demonstrating that the high-frequency coupling improves the model / drifter comparison in several respects.

Finally, I will show selected results from an in-press paper, on high-frequency (including sub-daily) precipitation variance in rain gauges, satellite products, and high-resolution coupled ocean/atmosphere models, including the GEOS / MITgcm simulation. Ben Kirtman and Leo Siqueira of RSMAS are co-authors on this in-press study.

Mar 16: NO SEMINAR (Spring Recess)


Mar 30: Hanjing Dai
Department of Ocean Sciences, RSMAS
(one-hour AMP student seminar)

Spatial and Temporal Measurements of Short Wind Waves Using
Shape From Polarization: Assumptions, Procedures, and Applications

Ocean surface roughness, an element controlled by ocean surface waves, is important in air-sea interaction studies and ocean remote sensing applications. Short waves having millimeter to meter wavelengths are the major contributor of ocean surface roughness, in terms of mean square slope. The common temporal measurements conducted by buoys or wave gauges to short waves is not successful due to the errors of instrument and the large Doppler frequency shift caused by surface currents. The spatial measurements of using laser or optical scanning sensors avoids the issues associated with the Doppler frequency shift but poorly estimating breaking waves characterized by the high void fraction white patches. The length scales of breaking waves also range from a few centimeters to a few decameters. As a result, reliable measurements of short gravity and capillary waves in the ocean are rare. Particularly the temporal and spatial measurements in millimeter to meter wavelength range are urgently needed. To retrieve the slopes of short wind waves in higher wavenumber domain (> 1 rad/m), the technique Shape from Polarization (SfP) developed by researchers in computer vision is applied to ocean surface polarization data measured by a polarization camera. We explore the assumptions and procedures for using SfP to calculate the 2D wave slope in the laboratory and field. A comparison made between different camera incidence angles found that the wave slope is a wavelength-dependent term, σ(λ), determined by true slope resolution of polarization camera system. A model consisting of only Rayleigh scattering under the clear sky was first proposed to extend SfP to the ocean surface wave slope retrieval affected by polarized skylight. Derived ocean surface wave slope showed a good agreement with the wind speed as Cox and Munk (1954) suggested. This paves the way for the applications of SfP in ocean remote sensing and encourages the widespread use of SfP in the future.


Apr 13: Dr. Alok Bhargava
University of Maryland School of Public Policy, College Park

Sea Surface Temperatures, Sea Ice Thicknesses,
and Ocean Surface Current Velocities
Recording Available at COMPASS ON DEMAND

This paper analyzed quarterly longitudinal data during 2000-2019 on sea surface temperatures, sea ice thicknesses, and ocean surface current zonal and meridional velocities in the Northern and Southern hemispheres. The methodological framework addressed issues such as the processing of remote sensing signals, interdependence between sea surface temperatures and sea ice thicknesses, and combining zonal and meridional velocities as eddy kinetic energy. The remote sensing data available at different resolutions were merged into a longitudinal database for 64,800 1×1 degree grids. Dynamic and static random effects models were estimated by maximum likelihood and stepwise methods, respectively, taking into account the unobserved heterogeneity across grids. The main findings were that quarterly sea surface temperatures increased steadily in the Northern hemisphere, whereas cyclical patterns were apparent in the Southern hemisphere; sea ice thicknesses declined steadily in the Northern hemisphere. Second, sea surface temperatures were estimated with large negative coefficients in the models for sea ice thicknesses in both hemispheres; previous sea ice thicknesses were negatively associated with sea surface temperatures thereby indicating feedback loops. Third, sea surface temperatures were positively and negatively associated with eddy kinetic energy in Northern and Southern hemispheres, respectively. Overall, the results indicated the importance of reducing sea surface temperatures via reductions in greenhouse gas emissions and dumping of pollutants in oceans for enhancing global sustainability.

Apr 14 (Thursday, MSC 343): Dr. Michel Boufadel
Department of Civil and Environmental Engineering / Center for Natural Resources
New Jersey Institute of Technology, Newark

Transport and Fate of Oil Spills Offshore and Onshore –
Report on Macroscale Investigations (Below the Meter Scale)
Recording Available at COMPASS ON DEMAND

Our group has been investigating oil spills for the last 15 years and was very involved in the efforts funded by the Gulf of Mexico Research Initiative, and our recent work has been funded by the Canadian Government for addressing bitumen oil. The talk addresses the movement of oil due to waves and the role of dispersant in altering the oil droplet size distribution. It also addresses the release of oil from underwater (blowout), a project led by the Consortium CARTHE led by Professor Ozgokmen of UMiami. We also report results of an investigation of oil in the beaches of the Gulf of Mexico. The results indicate that high salinity (exceeding 300 g/L) is likely the reason for the lack of oil biodegradation.

Michel Boufadel is Distinguished Professor of Environmental Engineering and Director of the Center for Natural Resources. He is a Professional Engineer in New Jersey, and a Board Certified Environmental Engineer in the USA. Dr. Boufadel served recently on four National Research Council (National Academies) committees in relation to oil spills.  He also served on a committee by the Royal Society of Canada on "The impact and behavior of oil in aquatic environments", and served on the Environmental Protection Agency (EPA) Science Advisory Board on natural gas extraction from shale formations (2011-2012). He is Editor in Chief of Marine Pollution Bulletin.


Apr 27: NO SEMINAR (OCE Student Town Hall Meeting)