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WRF SLP Bias IssuesUpdate from Santa Cruz meeting

Matt HigginsJohn CassanoMay 18, 2010

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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

shown: LW 4 SW 4 / no nudging, WRF 3.1.0

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SLP Bias Issue

Things could be worse

shown: Polar MM5 on wr50a domain

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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

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“The chosen one”

lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 2layers 1-20: no nudginglayers 21-30: linearly rampedlayers 31-40: full nudging

shown: sfdda wv2 rmp

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Additional Spectral Nudging Options

lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 1layers 1-20: no nudginglayers 21-40: full nudging

shown: sfdda wv1

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Additional Spectral Nudging Options

lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 2layers 1-20: no nudginglayers 21-40: full nudging

shown: sfdda wv2

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Additional Spectral Nudging Options

lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 3layers 1-20: no nudginglayers 21-40: full nudging

shown: sfdda wv3

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Additional Spectral Nudging Options

lw 4 sw 4 with spectral fdda for U, V, and T, max wave number 3layers 1-20: no nudginglayers 21-30: linearly rampedlayers 31-40: full nudging

shown: sfdda wv3 rmp

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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

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WRF 3.2.0, lw 4 sw 4 with spectral fdda, max wave 2layers 1-20: no nudginglayers 21-30: linearly blendlayers 31-40: full nudging

shown: lw 4 sw 4 3.2.0 wv2 rmp

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• 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