Arctic System Reanalysis (ASR)
The Arctic System Reanalysis is a multi-agency, university-led retrospective analysis (reanalysis) of the Greater Arctic. ASR is produced using high-resolution versions of the Polar Weather Forecast Model (PWRF) and the WRF-VAR and High Resolution Land Data Assimilation (HRLDAS) data assimilation systems that have been optimized for the Arctic. ASR is a comprehensive integration of the regional climate of the Arctic, currently for the period 2000-2012, with two versions: ASRv1 – 30 km and ASRv2 – 15 km; both are available through the NCAR Research Data Archive. Both versions have 29 pressure levels (71 model levels), 27 surface and 10 upper air analysis variables, 74 surface and 16 upper air forecast variables, and 3 soil variables. Both the u- and v- winds relative to grid and relative to earth are present in the final version.
New features in ASRv2 compared to ASRv1 are higher horizontal resolution, updated model physics including sub-grid scale cloud fraction interaction with radiation, and a dual outer loop routine for more accurate data assimilation. Surface and pressure level products are available at 3-hourly and monthly-mean timescales. ASRv2 will be updated through 2016, then re-assimilated (2000-2016) using the most recent version of Polar WRF and WRFDA (3.9.1). This newer version, ASRv2.1, should be available starting in mid-2018 and will be kept up-to-date through 2020 with a delay of ~3 months. [text credit: Aaron Wilson and David Bromwich]
Excellent reproduction of near-surface and tropospheric variables; for example ASRv2 captures two-thirds of the 3-hourly wind speed variance in surface observations, out-performing ASRv1 and ERA-Interim
The high-resolution topography and land surface resolve well the fine-scale processes such as topographically-forced winds and polar low
Marked improvement in summertime precipitation for ASRv2 versus ASRv1.
While ASRv2 forecast precipitation and downward radiation at the surface are improved over ASRv1, a dry bias is still present during the cooler months in ASRv2
Surplus downward shortwave and a small deficit downward longwave radiation still indicate room for improvement in cloud physics including aerosol concentrations and cloud-radiative feedbacks
ASRv1: : Bromwich, D., L. Bai, K. Hines, S. Wang, Z. Liu, H. Lin, Y. Kuo, and M. Barlage. 2012. Arctic System Reanalysis (ASR) Project. Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory. https://doi.org/10.5065/D6K072B5. Accessed† dd mmm yyyy.
ASRv2: National Center for Atmospheric Research/University Corporation for Atmospheric Research, and Polar Meteorology Group/Byrd Polar Research Center/The Ohio State University. 2017. Arctic System Reanalysis version 2. Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory. http://rda.ucar.edu/datasets/ds631.1/. Accessed† dd mmm yyyy.
Figure 2: Comparison showing left) ASRv2 mean 700 hPa relative humidity (%) and right) difference (%) between ASRv2 and ERAI for the period December 2006 – November 2007. Where the 700 hPa pressure level exists below ground based on the annual average surface pressure have been masked in gray. (contributed by A. Wilson)
Figure 4: Streamlines and wind speeds (colors) at 10-m for an intense orographically channeled wind event in Nares Strait on 9 February 2007 as captured by a) ASRv1 and b) ASRv2. Orographic channeling in Nares Strait may help generate persistent winter North Water polynya. ASRv2 resolves the orography of Nares Strait and thus the winds are much stronger (> 20 m s-1 ) and more continuous than ASRv1 (~15 m s-1). The katabatic winds over Greenland feed into the wind flow at two locations in ASRv2. There are multiple centers in the low over Baffin Bay in ASRv2 compared to the single center in ASRv1. (contributed by A. Wilson)
ASR v1; 30 km; 71 levels; 10hPA top,
ASR v2; 15 km; 71 levels; 10hPA top
30 km and 15 km
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