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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 8 | Copyright
Geosci. Model Dev., 11, 3347-3368, 2018
https://doi.org/10.5194/gmd-11-3347-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Development and technical paper 21 Aug 2018

Development and technical paper | 21 Aug 2018

Implementation of a simple thermodynamic sea ice scheme, SICE version 1.0-38h1, within the ALADIN–HIRLAM numerical weather prediction system version 38h1

Yurii Batrak1, Ekaterina Kourzeneva2, and Mariken Homleid1 Yurii Batrak et al.
  • 1Development Centre for Weather Forecasting, Norwegian Meteorological Institute, Oslo, Norway
  • 2Finnish Meteorological Institute, Helsinki, Finland

Abstract. Sea ice is an important factor affecting weather regimes, especially in polar regions. A lack of its representation in numerical weather prediction (NWP) systems leads to large errors. For example, in the HARMONIE–AROME model configuration of the ALADIN–HIRLAM NWP system, the mean absolute error in 2m temperature reaches 1.5°C after 15 forecast hours for Svalbard. A possible reason for this is that the sea ice properties are not reproduced correctly (there is no prognostic sea ice temperature in the model). Here, we develop a new simple sea ice scheme (SICE) and implement it in the ALADIN–HIRLAM NWP system in order to improve the forecast quality in areas influenced by sea ice. The new parameterization is evaluated using HARMONIE–AROME experiments covering the Svalbard and Gulf of Bothnia areas for a selected period in March–April 2013. It is found that using the SICE scheme improves the forecast, decreasing the value of the 2m temperature mean absolute error on average by 0.5°C in areas that are influenced by sea ice. The new scheme is sensitive to the representation of the form drag. The 10m wind speed bias increases on average by 0.4m s−1 when the form drag is not taken into account. Also, the performance of SICE in March–April 2013 and December 2015–December 2016 was studied by comparing modelling results with the sea ice surface temperature products from MODIS and VIIRS. The warm bias (of approximately 5°C) of the new scheme is indicated for areas of thick ice in the Arctic. Impacts of the SICE scheme on the modelling results and possibilities for future improvement of sea ice representation in the ALADIN–HIRLAM NWP system are discussed.

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The authors discuss the implementation and performance of a simple one-dimensional sea ice scheme within the ALADIN–HIRLAM numerical weather prediction system. This scheme is developed to replace the prescribed sea ice surface temperature that was used before. Numerical experiments over the large ice-covered areas of the European Arctic show that new scheme helps to improve the modelled 2 m temperature in regions that are influenced by sea ice, especially when the forecast is longer than 12 h.
The authors discuss the implementation and performance of a simple one-dimensional sea ice...
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