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DA-TT activities

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The DA-TT will foster the development and evaluation of data assimilation systems relevant to GOV. This addresses the issue identified in the GOV review of the need to coordinate fundamental and challenging issues in the ocean forecasting process, of which data assimilation is a significant part. The DA-TT will address this issue with the following objectives:

  1. To coordinate and improve the assimilation of ocean and sea-ice data into ocean, sea-ice and coupled models by:
    1. providing a forum for discussion of DA algorithms and their development, and fostering improved communication between DA researchers outside and within the GOV groups.
    2. creating a framework for inter-comparison of aspects of data assimilation schemes, distinct from those studied in the Inter-comparison and Validation Task Team (IV-TT)
  2. To provide a focus for diagnosing and understanding model and observation biases through the use of data assimilation techniques, and discussing the results with model developers and observation specialists.

The scope of the task team is defined as covering:

  • Global and regional scales, including coastal ocean data assimilation.
  • Systems used for near-real time ocean forecasting, seasonal forecasting, reanalysis, and research and development.
  • Physical ocean and sea-ice, coupled ocean/atmosphere/sea-ice/waves DA systems, and biogeochemical DA.
  • All aspects of the data assimilation process including: observation operators; error covariance estimation and representation (including both background and observation error covariances); minimisation algorithms; observation and model bias correction; initialisation; ensemble generation; analysis error estimation.
  • Both theoretical and practical implementation issues, including the efficiency and scalability of DA algorithms and codes on current and future high-performance computing architectures.
  • Development of metrics for assessment of data assimilation schemes.
  • Development of techniques for assimilating new observation types.
  • Development of observation impact and observation sensitivity techniques.

The development of techniques for assessing observation impacts and sensitivity and assimilation of new observation types will feed directly into the work of the OSEval-TT. Techniques for inter-comparison of DA outputs will be developed in conjunction with the IV-TT but will be distinct from the overall forecasting accuracy inter-comparison and validation carried out by the IV-TT as they will focus on specific parts of the data assimilation systems. Assimilation of biogeochemical variables will overlap with the work of the MEAP-TT, and the important issue of reducing the impact of physical DA on vertical velocities and therefore biogeochemistry will also address a fundamental problem in coupled physical-biogeochemical forecasting. Coupled data assimilation development will be a focus of the DA-TT, while the CP-TT will focus on the other challenges of coupled prediction. Since coastal and shelf-seas data assimilation has some common issues with deep ocean data assimilation, this will also be included in the scope of the DA-TT to provide a forum for sharing of ideas with COSS-TT.

The scope of the DA-TT therefore overlaps with the other GOV task teams. These overlaps can be managed by inviting co-chairs and/or members of the relevant task teams to attend meetings of the DA-TT, by organising joint meetings with other TTs, and by coordinating joint projects with other TTs.

The WMO data assimilation symposium series is the main international forum for discussing the scientific aspects of data assimilation and includes ocean, atmosphere, coupled and other DA. AGU, EGU and similar scientific meetings also have DA sessions. Meetings of the DA-TT will be more focussed on ocean and sea-ice than those other meetings, and are expected to lead to collaborative projects which those meetings do not foster. WMO has a data assimilation group that has a similar remit within the atmospheric community, while IICWG has a Data Assimilation Working Group, and the DA-TT will liaise with both of these groups . The collocation of DA-TT meetings with other TT meetings, and other international meetings, will therefore be required to avoid excessive travel requirements for TT members.

 

February 2016