1. WRF SLP Bias Issues Update from Santa Cruz meeting Matt Higgins John Cassano May 18, 2010 1

2. SLP Bias Issue As mentioned at the Santa Cruz meeting, WRF atmospheric simulations have shown significant high SLP bias in the N. Pacific Shown is the “best case” of the many non- nudging options examined 2 shown: LW 4 SW 4 / no nudging, WRF 3.1.0

3. 3 SLP Bias Issue Things could be worse shown: Polar MM5 on wr50a domain

4. 4 Physics options: control mp 10 pbl, sfl 1 no fractional ice lw 4, sw 4 lw 4, sw 4 and cu_physics 1 lw 4, sw 4 and cudt 0 Dynamics options: lw 4, sw 4, damp_opt 1, dampcoef 0.01 lw 4, sw 4, damp_opt 1, dampcoef 0.10 lw 4, sw 4, damp_opt 3, dampcoef 0.20 lw 4, sw 4, gwd_opt 1, coarse topo lw 4, sw 4, gwd_opt 1, normal topo Domain size changes: XL (top inc. by 2,000 km) wr50b (top dec. by 2,000 km) wr50c (left dec. by 2,000 km) wr50d (smallest domain that fits POP) wr50e (bottom dec. by 2,000 km) wr50f (bottom inc. by 2,000 km) wr50g (bottom dec. by 800 km) BPRC related simulations: BPRC recommend physics Polar WRF, all defaults Polar WRF, only alt temp surf Polar WRF, all defaults, BRPC rec. physics Other simulations: WRF 3.1.0 w/ WRF 3.1.1 landuse.tbl WRF 3.1.1 WRF 3.2.0 era-interim forcing Polar MM5 lw 4, sw 4 and smooth_cg_topo 10 pt relaxation zone exponential ramping (spec_exp = 0.33) sea ice albedo fix on pingo sea ice thermal conductivity fix sea ice thermal conductivity fix (alternate fix) Nudging options gridded fdda (top 20 layers) gridded fdda for 3 days, then off (top 20 layers) spectral fdda, only geopotential (top 20) spectral fdda, only u, v, and T (top 20) spectral, uvt, max wv 1 (top 20) spectral, uvt, max wv 2 (top 20) spectral, uvt, max wv 3 (top 20) spectral, uvt, max wv 2 (ramped 20->30, full 30-40) spectral, uvt, max wv 3 (ramped 20->30, full 30-40) WRF 3.2, spectral, uvt, max wv 2 (ramped 20->30, full 30-40) All WRF physics and dynamics options examined ~45 different simulations

5. 5 “The chosen one” lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 2 layers 1-20: no nudging layers 21-30: linearly ramped layers 31-40: full nudging shown: sfdda wv2 rmp

6. 6 Additional Spectral Nudging Options lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 1 layers 1-20: no nudging layers 21-40: full nudging shown: sfdda wv1

7. 7 Additional Spectral Nudging Options lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 2 layers 1-20: no nudging layers 21-40: full nudging shown: sfdda wv2

8. 8 Additional Spectral Nudging Options lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 3 layers 1-20: no nudging layers 21-40: full nudging shown: sfdda wv3

9. 9 Additional Spectral Nudging Options lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 3 layers 1-20: no nudging layers 21-30: linearly ramped layers 31-40: full nudging shown: sfdda wv3 rmp

10. 10 WRF 3.2 WRF 3.2.0, no nudging (same namelist as previous best WRF 3.1.0 option, slide #2) shown: lw 4 sw 4 3.2.0

11. 11 WRF 3.2.0, lw 4 sw 4 with spectral fdda, max wave 2 layers 1-20: no nudging layers 21-30: linearly blend layers 31-40: full nudging shown: lw 4 sw 4 3.2.0 wv2 rmp

12. 12 1989-2007 on wr50a domain Same physics namelist as RACM (40 levels, Goddard microphysics, RRTMG longwave and shortwave, MYJ boundary layer / surface layer, Noah LSM ERA-Interim initialization on Jan 1, 1989 with ERA-Interim lateral boundary conditions and skin temperature SMMR and DMSP SSM/I Bootstrap sea ice concentrations from NSIDC Currently running two sets of simulations: WRF 3.2 with and without spectral nudging Spectral nudging simulations use nudging for U, V, and T, have a max wave number of 2, are ramped from layers 21-30 and full for 31-40 CORDEX Simulations