Systematic Improvements to Reanalyses of The Arctic (SIRTA) White Paper Now Available for Community Review

June 29, 2016
By Jessica Rohde

A draft white paper, which has been prepared at the request of the Interagency Arctic Research Policy Committee (IARPC), is now available for community review and comment. This white paper on atmospheric reanalyses, with a focus on issues related to Arctic reanalyses, was requested in May 2015 by the IARPC Principals. A small working group was formed in the fall of 2015 under the leadership of Richard Cullather, Tom Hamill, David Bromwich and Xingren Wu. The working group held four open meetings for the community to share ideas and provide input to the white paper.

The working group was asked to develop a white paper to:

  1. Evaluate the state, utilization, limitations and potential utility of the current Arctic reanalyses;
  2. Inventory and assess the currently planned operational and experimental observations of the Arctic system to improve reanalyses;
  3. Examine reanalyses products and forecast models for potential improvement; and
  4. Assess the potential utility of Year of Polar Prediction and Coupled Model Intercomparison Project 6 as focal points to facilitate progress.

Reanalyses are retrospective, gridded depictions of the atmosphere. Reanalyses are generated through a statistical adjustment of a prior, short-term numerical forecast to available observations during the period of the forecast. The data include radiance information from available satellites and in situ observations, including land stations, marine observations, aircraft, rawinsonde, and profiler data. Compared to mid-latitudes, the Arctic has a paucity of in situ observations. Additionally, both infrared and microwave satellite sensors have difficulty in profiling the lower atmosphere over snow- and ice-covered surfaces, and geostationary satellites do not cover the high latitudes.

Improving reanalyses will help in nearly all aspects of Arctic systems research, including physical process-related investigations, and the evaluation of weather and climate models. Reanalyses are also used as boundary conditions for a variety of other models, including those for the regional Arctic atmosphere, ocean circulation and sea ice, land surface, ice sheets, and biogeochemistry. Importantly, they are also used in the productionof satellite-derived data sets. Reanalyses are critical for understanding the Arctic climate system due to the lack of conventional data sources. Potentially, reanalyses are powerful tools that may be used to address major scientific questions, including Arctic predictability and polar/midlatitude climate interactions. Many Arctic system studies and applications cannot be conducted without reanalyses.

You may access the White Paper here. You may submit comments and suggestion to the authors through the IARPC secretariat by sending an email to Sara Bowden ( There will be an open Town Hall meeting on Monday, July 11. For more information click here.

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