Previous Seminars

Crossing the Southern Ocean: How the parameterization of poleward heat transport may differ from that of the real world

Speaker: 
Matthew Hecht
Affiliation: 
LANL, USA
Seminar Date: 
22. October 2018 - 12:30 - 13:10

As the only major ocean basin that allows for circumpolar flow, with no continental boundaries against which zonal pressure gradients may be established, the Southern Ocean has been singled out as a region in which transient mesoscale eddies are especially important. When effects of bathymetry on the flow are considered, however, transient eddies alone need not generate the entire poleward heat transport that compensates the equatorward heat transport forced by the prevailing westerly winds.

Measuring Arctic amplification

Speaker: 
Richard Davy
Seminar Date: 
9. October 2018 - 11:15 - 11:45

One of the defining features of both recent and historical cases of global climate change is Arctic Amplification (AA). This is the more rapid change in the surface air temperature (SAT) in the Arctic compared to some wider reference region, such as the Northern Hemisphere (NH) mean. Many different metrics have been developed to quantify the degree of AA based on SAT anomalies, trends and variability. The use of different metrics, as well as the choice of dataset to use can affect conclusions about the magnitude and temporal variability of AA.

Simultaneous ensemble-based state and parameter estimation for earth systems

Speaker: 
Fuqing Zhang
Affiliation: 
Pennsylvania State University
Seminar Date: 
28. September 2018 - 11:00 - 12:00

We seek to develop and apply a generalized data assimilation framework using Ensemble-based Simultaneous State and Parameter Estimation (ESSPE) that will facilitate data-model integration and uncertainty quantification for the broad weather, climate and earth science communities.

Cross shelf dynamics in the Agulhas Current region from GlobCurrent and glider observations

Speaker: 
Tumelo Maja
Affiliation: 
Nansen-Tutu, University of Cape Town, South Africa and Council for Scientific and Industrial Research
Seminar Date: 
27. September 2018 - 12:30 - 13:00

The Agulhas Current is the strongest western boundary current in the southern hemisphere and a major driver of variability for coastal regions along South Africa’s eastern shores. Interactions between the Agulhas Current and the steep and narrow continental shelf drive a range of instabilities at the meso (50 – 200 km) and sub-meso (<10 km) scales, such as the shedding of eddies, plumes and filaments, as well as the meandering or intrusion of the current onto the shelf (Krug et al., 2017).

Satellite chl-a image inpaintin

Speaker: 
Julien Brajard
Affiliation: 
LOCEAN, Sorbonne Université, NERSC
Seminar Date: 
25. September 2018 - 12:00 - 12:30

In this work, we evaluate the efficiency of a deep-convolutional neural network (CNN) to reconstruct missing data in chlorophyll-a satellite images. The missing area are mainly due to the presence of cloud above the ocean. The CNN-based methodology is compared with a sate-of-art krigging algorithm.

Using the Ensemble Kalman Filter to estimate turbulence model parameters: Intermediate results

Speaker: 
Simon Clement
Seminar Date: 
5. September 2018 - 12:30 - 13:00

Our ultimate goal is to compute the contextual model evidence in a 1D energy- length-scale turbulence closure model, and to use this model evidence to perform model selection.
In particular, contextual model evidence would be used to estimate parameters of the turbulence-closure and more generally to select the best parametrisation of the turbulence.
We use the EnKF-N to perform state estimation, and test its performance first by using a twin experiments setup with synthetic observations.

Greenland Ice Sheet mass balance and climate interactions

Speaker: 
Prof. Edward Hanna
Affiliation: 
School of Geography and Lincoln Centre for Water and Planetary Health, College of Science, University of Lincoln, UK
Seminar Date: 
30. August 2018 - 12:30 - 13:15

The rate of mass loss from the Greenland Ice Sheet (GrIS) has tripled over the last 20 years, reflecting strong climate warming over the region. Here I will present a review of some of the Greenland mass-balance evaluations that I have been involved with over the last 15 years. We will also review other recent estimates of GrIS mass change, including some very recent observational updates from satellite data, noting the impacts on global sea-level rise.

Arctic Amplification and mid-latitude extreme weather

Speaker: 
Prof. Edward Hanna
Affiliation: 
School of Geography and Lincoln Centre for Water and Planetary Health, College of Science, University of Lincoln, UK
Seminar Date: 
29. August 2018 - 11:15 - 12:00

Recently there has been a significant increase in some types of extreme weather over the UK and other northern mid-latitudes: for example winters 2013/14 & 2015/16 in the UK were exceptionally mild, wet and stormy, while large parts of winters 2009/10 and 2010-11 were unusually cold and had record deep snows. Snowmageddon hit the eastern seaboard of the USA in the last few winters. Meanwhile several recent summers, most notably 2007 and 2012, experienced record UK rainfall and widespread flooding.

Optimization of stochastic parameterizations for model error treatment using nested ensemble Kalman filters

Speaker: 
Guillermo Scheffler
Affiliation: 
University of Buenos Aires, Argentina
Seminar Date: 
16. August 2018 - 12:30 - 13:00

Stochastic parameterizations have been successfully used to represent the uncertainty associated with the parameterization of unresolved scale processes for ensemble forecasting and data assimilation systems. In order to accurately describe the uncertainty associated with numerical predictions, these parameterizations have to be optimized. We will introduce a novel technique based on hierarchical ensemble Kalman filters for the optimization of stochastic parameterizations for data assimilation applications.

Liouville solutions for low complexity systems: characterisation of PDF evolutions

Speaker: 
Alejandro Hermoso
Affiliation: 
University of Balearic Islands.
Seminar Date: 
13. July 2018 - 11:00 - 11:30

The prediction of weather and climate is one of the most challenging problems faced nowadays by the scientific community, not only for its incalculable value for macroevolution planning but also for civil protection and man- agement of a myriad of socioeconomic assets. One of the main causes why numerical weather forecasts made with dynamical models are uncertain is the lack of knowledge about the state of the atmosphere with infinite preci- sion.