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Ice assimilation in Reanalysis UR025.4

Ice assimilation in Reanalysis UR025.4. Hao Zuo, Maria Valdivieso and Keith Haines ESSC, University of Reading. Summary of the Reanalysis.

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Ice assimilation in Reanalysis UR025.4

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  1. Ice assimilation in Reanalysis UR025.4 Hao Zuo, Maria Valdivieso and Keith Haines ESSC, University of Reading

  2. Summary of the Reanalysis • The model configuration: NEMO version 3.2 in ORCA025 configuration, 1/4 degree horizontal resolution with 75 vertical levels (1m - 200 m), TKE vertical mixing scheme, coupled with LIM2 ice model. • The assimilation: a version of the operational NEMO-FOAM system (Storkey et al. 2010) with an assimilation window of 5-day. • Observations:satellite SST data from AVHRR and AATSR. in-situ SST data from OSTIA project (Stark et al., 2007). Altimeter SLA data from the Jason-1, Jason-2, Topex/Poseidon, ERS, and Envisat platforms. The reprocessed sea-ice concentration data from OSI-SAF. • Meteorological Forcing: ECMWF ERA-Interim atmospheric reanalysis (Simmons et. al., 2007; Dee and Uppala, 2009). • Experiment: The NEMO-FOAM reanalysis was initialised from EN3 climatology and run from 1989 - 2010.

  3. FOAMv1 only assimilates ice concentration obs bck mean error Ice volume is not conserved during FOAM assimilation FOAM changes ice concentration without updating ice thickness accordingly, in addition, a minimum ice thickness (0.5 m) is added whenever ice concentration increases from 0.

  4. UR025.4 shows a similar Arctic ice anomaly trend to PIOMAS model, but with much less ice volume in seasonal mean

  5. UR025.4 lost MY ice and ice is too thin comparing with ICESAT data UR025.4 UR025.3 UR025.3 do not assimilate ice and produce much thicker ice over the Arctic region 0.8 3 1 1.2 3.5 4

  6. UR025.3 has better Arctic ice volume comparing with UR025.4, but with poor distribution pattern

  7. background observation obs-bck analysis Day 0 background icecenc forecast forecast errors Day 5 1 increments IAU 0 5day 10day 15day 20day time

  8. Ice condition Sep 1989 ice conc UR025.3 Test35 (iceconc < 0.9) UR025.4 Test34 (icethick < 2m) ice thic

  9. Ice condition Sep 1989 Test35 switch off ice assimilation whenever ice concentration > 0.9 Ice concentration Ice thickness Test35-UR025.4 Test34 switch off ice assimilation whenever ice thickness > 2 m Test34-UR025.4

  10. UR025.4 AMOC at 26.5 N comparing with RAPID observation

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