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MERRA reanalysis budget lessons about GCM errors in the W . Atlantic / IAS region

MERRA reanalysis budget lessons about GCM errors in the W . Atlantic / IAS region. Brian Mapes Univ. of Miami. MERRA reanalysis. MERRA = Modern Era (from 1979) Reanalysis for Research and Applications Uses GEOS-5 GCM (formerly NSIPP) ½ x 2/3 deg resolution

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MERRA reanalysis budget lessons about GCM errors in the W . Atlantic / IAS region

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  1. MERRA reanalysis budget lessons about GCM errors in the W. Atlantic / IAS region Brian Mapes Univ. of Miami

  2. MERRA reanalysis MERRA = Modern Era (from 1979) Reanalysis for Research and Applications Uses GEOS-5 GCM (formerly NSIPP) ½ x 2/3 deg resolution 3D state estimation process Budgets balance exactly albeit with “analysis tendencies” built by Incremental Analysis Updating (IAU)

  3. MERRA’s variables Z [T,u,v,qv] satisfy: ΔZ/Δt = Żmodel + Żana ΔZ/Δt = (Żdyn + Żphys)+ Żana Oops -- missed by EZ! Adjust Żana by -2EZ/Δt and try again from t-Δt/2 EZ EZ oops some analyzed values Z at some point Cost: 1.5x free model run Żana(t) saved as a data set time (6h increments)

  4. Learning from analysis tendencies ✔ ✔ (ΔZ/Δt)obs = (Żdyn + Żphys)+ Żana • If state is kept accurate (LS flow & gradients), then (ΔZ/Δt)obs and advective terms Żdyn will be accurate • and thus Żana ≅ -(error in Żphys)

  5. Vertically integrated qv tendencies: • mst = moist physics (convection + LS condens.) • ana = analysis tendency (~ –phys. error) • Summer climatologies:

  6. Moist physics (conv. + LS) <0 a sink of water vapor

  7. Analysis is moistening this area, presumably because physics is an excessive sink (raining too much)

  8. Precipitation bias

  9. rainy bias in all reanalyses

  10. rainy bias in all reanalyses

  11. Dynamical side: U analysis tendenciesoverlaid with {u,v} vectors 850 1000mb 500 700

  12. U analysis tendenciesoverlaid with {u,v} vectors 60-90W Zonal mean 850 1000mb 500 700 60-90W Zonal mean

  13. Analysis tends. on mass and wind fields: fighting the model’s excessive baroclinic vortex Cyclonic analysis torque: Lower thickness wanted for thermal wind balance Anticyclonic analysis torque Higher thickness wanted

  14. Analysis tends. on mass and wind fields: fighting model’s excessive baroclinic vortex Cyclonic analysis torque: Anticyclonic analysis torque

  15. Way too much: analysis opposes mean deep convective heating(with this model’s peculiar characteristic profile) open contours: model physics heating

  16. GEOS-5 model’s peculiar heating profile in tropical deep convection dT/dt_mst in TOGA COARE 15 day time section at a grid point Strange cooling spike at 700: misplaced melting (should be 550 mb)

  17. largest value on globe: >3 m/s per day u deceleration by analysis tendency (obs fighting model)

  18. warm SST season (later than summer)

  19. Conclusions • Analysis tendencies ~ -model systematic errors • Obs chronically nudging model a certain way • MERRA W. Atl. has too much deep convection • excessive precip relative to GPCP/CMAP • excessive qv sink (fought by pos. qv anal. tendency) • excessive baroclinic vorticity couplet 600mb/200mb • includes largest u200 analysis tendency on the planet • seasonality: late summer (warm SST season) • T’ errors in thermal wind balanced sense w/ above • Just excessive strength: opposes mean moist Q • profile is distinctive, erroneous: melting at 700 mb instead of 550 • Familiar: shallow v. deep convection problem

  20. Thank you http://www.ncdc.noaa.gov/gibbs/image/GOE-12/WV/2006-07-14-15

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