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.

read more

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.

read more

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.

read more

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.

read more

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.

read more

Creating a Madden-Julian oscillation (MJO) without convection

Speaker: 
Dr Jun-Ichi Yano

Affiliation: 
Meteo France

Seminar Date: 
12. July 2018 - 12:15 - 13:00

The Madden--Julian oscillation (MJO), a planetary--scale eastward propagating coherent structure with periods of 30--60 days, is a prominent manifestation of intraseasonal variability in the tropical atmosphere.
It is widely presumed that small--scale moist cumulus convection is a critical part of its dynamics.
However, the recent results from high--resolution modeling as well as data analysis suggest that the MJO may be understood by dry dynamics to a leading--order approximation.

read more

Introductory Course On Statistical Modeling Of Extreme Values

Speaker: 
Hans Wackernagel

Affiliation: 
Equipe de GEOSTATISTIQUE - MINES ParisTech - PSL

Seminar Date: 
31. May 2018 - 10:15 - 1. June 2018 - 15:00

Extreme value theory is based on different principles than those
of conventional statistics as it is designed to study and model
exceptional events rather than the average characteristics of
natural phenomena.

This two-day introductory course will start by presenting
exploratory tools to analyze the behavior of extreme values in
geophysical data. This will help to motivate the basic principles
of the statistical modeling of extreme values and the
distributions that characterize them. The two common approaches
for assessing the risk of extreme events at a given level, i.e.

read more

Impact of Winter Storms in a Thinner Arctic Sea-ice Regime

Speaker: 
Polona Itkin

Affiliation: 
Norwegian Polar Institute

Seminar Date: 
5. June 2018 - 10:00 - 11:00

The integrative effects of increased winter storm activity in the Arctic's Atlantic sector were studied using a collection of field observations and analyses. In early 2015, during the six-month N-ICE2015 expedition in the pack ice north of Svalbard, we observed a chain of events in the atmosphere-ice-ocean system that was triggered by several powerful winter storms. Our unique, interdisciplinary observations show that these winter storms entail significant effects that last much longer than the short-lived storm events themselves.

read more