Arctic System Reanalysis (ASR) IPY Project (Collaboration among UCAR, OSU, CU, and U. of Illinois) Reanalysis (e.g., ERA40, ERA-Interim, NCEP/NCAR…) over the Arctic Focus is on monitoring rapid Arctic change (e.g., recent sea-ice retreat and permafrost melting) 11 years (2000-2010) with a 10km Polar WRF/WRF- Var system (1081x1081x71 grids) COSMIC’s interest is climate impact and effective use of GPS RO to the direction GPS RO data along with all other data from operational data stream are being assimilated including radiances Already showing significant positive impact of GPS RO data (Z. Liu, MMM) There still exists room for improvement especially distinct refractivity bias in stratospheric altitudes - Misusing geometric height as GPH - Use of inadequate form of hydrostatic eq. - Temperature initialization error due to θ interpolation - Imperfect upper boundary condition and wave reflection Control GPS

Well then, is model the only one to blame? Bending angle optimization, as an example