Seminar

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Weekly Lunch Seminars / Thursday Seminars - an open seminar for all

Chasing Water: How ocean currents transport plastic and plankton around the globe

Speaker: 
Erik van Sebille
Affiliation: 
Institute for Marine and Atmospheric Research, Utrecht University, Netherlands
Seminar Date: 
21. October 2019 - 11:15

The ocean is in constant motion, with water circulating within and flowing between basins. As the water moves around, it caries heat and nutrients, as well as planktonic organisms and plastic litter around the globe.

The most natural way to study the pathways of water and the connections between ocean basins is using particle trajectories. The trajectories can come from computing of virtual floats in high-resolution ocean models.

Sparse Representation based on Dictionary Learning

Speaker: 
Ricardo Soares
Affiliation: 
NORCE Energy
Seminar Date: 
16. October 2019 - 11:15 - 11:45

This work presents the use of the Dictionary Learning method for a sparse representation of 4D seismic data. We consider a trade-off between the number of nonzero coefficients retained in the sparse data representation, the computational cost, and how well we can capture the main features of the original 4D seismic signal. K-SVD is an iterative algorithm used in Dictionary Learning that alternates between the calculation of the sparse representation vector and dictionary update. The algorithm starts with the definition of an initial dictionary (Discrete Cosine Transform, for instance).

Physical and biogeochemical variability off Baja California (Mexico): insights from numerical NPZD ocean models

Speaker: 
David Rivas
Affiliation: 
CICESE
Seminar Date: 
30. August 2019 - 13:15 - 14:00

Physical-biogeochemical Nitrate-Phytoplankton-Zooplankton-Detritus (NPZD)
numerical models are used to study the variability of nutrients and
phytoplankton biomass in coastal waters off Baja California Peninsula, a
region of high socioeconomic importance located in the southern California
Current System. The focus of these analyses has been the effects of
interannual climatic anomalies. For example, the year 2006 was anomalously
warm and with low chlorophyll (Chl) levels, associated with warm phases of
El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation

Lagrangian ocean analysis to study the physical mechanisms driving the processes occurring in the Greater Agulhas Current System

Speaker: 
Michael Hart-Davis
Seminar Date: 
13. August 2019 - 11:15 - 11:45

Lagrangian ocean analysis is a powerful way to study ocean processes from in-situ observations and numerical model simulations. As numerical modelling capabilities develop and physical mechanisms of the ocean are better understood, the importance of particle trajectory modelling continues to increase. Therefore, developing cross-disciplinary particle trajectory model applications for the Greater Agulhas System is highly relevant due to its potential contribution to scientific studies and operational applications.

Explore dynamical information with Pseudo-orbit Data Assimilation

Speaker: 
HAILIANG DU
Affiliation: 
Durham University
Seminar Date: 
13. June 2019 - 11:00 - 12:00

Physical processes such as the weather are usually modeled using nonlinear dynamical systems. Traditional statistical approaches are found to be difficult to draw dynamical information from the nonlinear dynamics. This talk is focusing on exploring dynamical information with Pseduo-orbit data assimilation to address various problems encountered in analyzing and modeling nonlinear dynamical systems. The talk will start with solving an “impossible” challenge pointed out by Berliner (1991) when applying the Bayesian paradigm to state estimation in chaotic systems.

Korea Satellite Remote Sensing of the Arctic

Speaker: 
Hyun-Cheol Kim
Affiliation: 
Korea Polar Research Institute (KOPRI)
Seminar Date: 
28. March 2019 - 15:00 - 15:30

Dr. Hyun-Cheol Kim is the director of Unit of Arctic Sea-Ice Prediction, Korea Polar Research Institute (KOPRI).
As a remote sensing scientist, he will give us a talk regarding the research activities of KOPRI.
After the seminar, NERSC and KOPRI will sign a MoU.

The challenge of bounded, non-Gaussian, non-linear and multi-scale variables

Speaker: 
Craig Bishop
Affiliation: 
School of Earth Sciences and ARC Centre of Excellence for Climate Extremes University of Melbourne
Seminar Date: 
8. April 2019 - 11:00 - 12:00

Current state estimation or data assimilation techniques assume Gaussian uncertainties for both forecasts and observations. However, unbiased observations of bounded variables can be shown to have highly non-Gaussian uncertainties and observation error standard deviations that depend on the value of the unknown true state. In particular, the observation error variance of such observations must tend to zero as the unknown true state tends to zero.

Impact of sea ice sources on calibrating a wave-ice interaction model

Speaker: 
Sukun Cheng
Affiliation: 
NERSC
Seminar Date: 
22. March 2019 - 11:00 - 11:30

Because of the interaction between ocean wave and sea ice, reliable models for wave propagation in the ice-covered region is critical to sea ice morphology. We present calibration of a viscoelastic type wave-in-ice model with wave, wind, and ice data collected from the Beaufort and Chukchi seas in the autumn of 2015. The data were from multiple sources of in-situ and remote sensing measurements in the marginal ice zone during the ice advance season.

Sea Ice Parameter Retrieval with Physical Synergy of Active and Passive Satellite Data

Speaker: 
Dr. Shiming Xu
Affiliation: 
Department of Earth System Science, Tsinghua University, China
Seminar Date: 
27. March 2019 - 13:00 - 13:45

Sea ice is a key component in the global climate system. Satellite remote sensing is the major approach to the basin-scale observation of sea ice, informing the community of key findings including accelerated shrinkage and drastic thinning of the sea ice cover. As the major method for the estimation of sea ice thickness, satellite altimetry is hindered by the snow cover over the sea ice, which introduces large uncertainty to the sea ice thickness retrieval. Meanwhile, the snow over is a direct indicator of polar hydrological cycle, and a key modulating factor of air-ice-sea interaction.

Model Calibration Using Warping Metrics: With Application to Sea Ice Deformation in MPM-ice

Speaker: 
Christian Sampson
Affiliation: 
University of North Carolina in Chapel Hill
Seminar Date: 
25. February 2019 - 11:30 - 12:00

Sea Ice is a critical component of earth’s climate system and mediates a broad range of physical processes in the Arctic, such as ocean-atmosphere interaction. Increased warming in the Arctic has drastically changed sea ice dynamics in the region and the ice composition, thinner and more first year ice, and an increased marginal ice zone. Accurate representation of lead formation is now more important than ever for the calculation of important climatological variables, such as oceanic heat flux.

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