Previous Seminars

Hydrological modelling & Data Assimilation (at catchment scale)

Speaker: 
Marc Etienne Ridler
Affiliation: 
DHI Group, Copenhagen, Dk
Seminar Date: 
29. June 2017 - 12:30 - 13:00

Hydrological models are used extensively to monitor and manage water resources, and provide flood forecasts. These complex, physically based models are inherently uncertain due to imperfect parameterization, meteorological forcing data, initial conditions, and model discretization. Data assimilation offers a means to incorporate information from measurements to both correct model forecasts and, importantly, provides quantitative uncertainty estimates useful for decision makers.

Presentation of IT-group

Speaker: 
Lars-Gunnar Persson (IT Group)
Seminar Date: 
13. June 2017 - 11:15 - 11:45

Information about our IT services and tasks challenges in IT security.

Estimating model evidence using ensemble-based data assimilation with localization - The model selection problem

Speaker: 
Sammy Metref
Affiliation: 
IFAECI, CNRS-CONICET-UBA, Buenos Aires, Argentina.
Seminar Date: 
31. May 2017 - 11:00 - 11:30

In recent years, there has been a growing interest in applying data
assimilation (DA) methods, originally designed for state estimation, to
the model selection problem. Along this stream of efforts, a contextual
formulation of model evidence (CME) has recently been introduced in
Carrassi et al. (2017) and it has been shown that it can be efficiently
computed using a hierarchy of ensemble-based DA procedures. While the DA
methods analyzed in Carrassi et al. (2017) cover those operationally
used worldwide for atmosphere or ocean prediction, they were not studied

Improving the sea ice thickness of TOPAZ by the merged weekly product from Cryosat2 and SMOS

Speaker: 
Jiping Xie from Ocean Modeling
Seminar Date: 
30. May 2017 - 11:15 - 11:45

A merged measurements of Sea Ice Thickness (SIT) from CryoSat2 and SMOS has been distributed in recent years. This product is weekly during the cold season and available since October 2010. As a potential operational SIT observation in Arctic, the quantitative evaluation of its impact on the performance of TOPAZ, which represents the Arctic component of the Copernicus Marine Environment Monitoring Service (CMEMS), is an essential issue due to the well-known SIT errors in most marine forecast systems.

Assimilation of non-conventional observations. Application to the estimating of ocean surface currents.

Speaker: 
Julien Brajard
Affiliation: 
LOCEAN/IPSL, Sorbonne Université, Paris, France
Seminar Date: 
29. May 2017 - 11:00 - 11:30

Data assimilation consists in optimally combining observations of a system with
outputs of a numerical model. In the traditional approaches, observations are
are considered to be eulerian and scalar. Recently, in the field
of earth and ocean observations, there is an increasing number of observations
that are fundamentally non-eulerian and/or non scalars:
Drifters and floats are advected by currents and bring a Lagrangian observation through their successive positions,
satellite data are measuring images that contains structured patterns.

Data assimilation of sea ice concentration: a twin experiment within the Norwegian Climate Prediction Model

Speaker: 
Madlen Kimmritz from Climate Dynamics and Prediction
Seminar Date: 
16. May 2017 - 11:15 - 11:45

A method capable of constraining the sea ice of a coupled climate system in a dynamically consistent manner would be of crucial societal importance.
It would allow for more accurate and reliable reconstruction of the climate that would improve the understanding of the sensitivity of our climate to anthropogenic forcing and enhance the skill of climate prediction on seasonal-to-decadal time scale.

Urban heat island effect in the Arctic

Speaker: 
Victoria Miles from Climate Processes
Seminar Date: 
2. May 2017 - 11:15 - 11:45

Urbanization in the Arctic and sub-Arctic is an increasingly important anthropogenic influence on climate, and has significantly affected terrestrial ecosystems. One of the most evident effects associated with urbanization is the urban heat island (UHI), when urban and suburban areas are warmer then rural areas. The effect is more pronounced in the high latitudes.

Wave-ice interactions in the neXtSIM sea-ice model

Speaker: 
Timothy Williams
Affiliation: 
NERSC
Seminar Date: 
27. April 2017 - 12:30 - 13:00

We have added a waves-in-ice model (WIM) into the new sea ice model neXtSIM. The physical effects included so far are the effect of the wave radiation stress (WRS) on the ice drift. Specifically, as waves travel into the ice, they are attenuated and lose momentum. This momentum could go into the ocean or the ice (or the atmosphere), but we transfer it entirely to the ice. The WRS, which is the flux of momentum from the waves to the ice, is relatively high at the ice edge but decays exponentially into the ice (like the wave energy).

Decadal Changes in Salinity in the Oceanic Subtropical Gyres

Speaker: 
Subrahmanyam (Subra) Bulusu
Affiliation: 
Satellite Oceanography Laboratory,School of the Earth, Ocean and Environment, University of South Carolina
Seminar Date: 
19. April 2017 - 11:00 - 12:00

There is evidence that the global water cycle has been undergoing an intensification over several decades as a response to increasing atmospheric temperatures, particularly in regions with skewed evaporation – precipitation (E-P) patterns such as the oceanic subtropical gyres. Moreover, observational data (rain gauges, etc.) are quite sparse over such areas due to the inaccessibility of open ocean regions. We analyzed spatial and temporal salinity trends in five subtropical gyre regions over the past six decades using Simple Ocean Data Assimilation (SODA) reanalysis.

Influence of Madagascar Ridge on ocean mesoscale eddies in a regional ocean model

Speaker: 
Issufo Halo
Affiliation: 
1) Department of Conservation and Marine Sciences, Cape Peninsula University of Technology, Cape Town, South Africa, 8000 2) Nansen-Tutu Centre for Marine Environmental Research, Oceanography Department, University of Cape Town, South Africa, 7700
Seminar Date: 
5. April 2017 - 13:00 - 13:30

The topography of the world's ocean basins are among the least studied oceanographic environments. However, they are fundamental for understanding the oceanic circulation. In this study the role of the Madagascar Ridge on modulating the mesoscale circulation, more specifically the eddy field is being investigated using two climatological solutions derived from a regional ocean model, ROMS. In the first experiment the model runs with an ordinary GEBCO-01 topography, whereas in the second, it runs with a modified topography, where the Madagascar Ridge has been removed.