MERRA reanalysis budget lessons about GCM errors in the W . Atlantic / IAS region
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Transcript of 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 MapesUniv. 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 resolution3D state estimation process
Budgets balance exactly albeit with “analysis tendencies” built by Incremental Analysis Updating (IAU)
some analyzed
values
Z at some point
time (6h increments)
ΔZ/Δt = Żmodel + Żana
ΔZ/Δt = (Żdyn + Żphys) + Żana
MERRA’s variables Z [T,u,v,qv]satisfy: Oops -- missed by EZ! Adjust
Żana by -2EZ/Δt and try again from t-Δt/2
EZ oops
Cost: 1.5x free model runŻana(t) saved as a data set
EZ
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)
✔✔
Vertically integrated qv tendencies:
• mst = moist physics (convection + LS condens.) • ana = analysis tendency (~ –phys. error)
• Summer climatologies:
Analysis is moistening this area, presumably because physics is an excessive sink (raining too much)
Precipitation bias
rainy bias in all reanalyses
rainy bias in all reanalyses
Dynamical side: U analysis tendenciesoverlaid with {u,v} vectors
1000mb 850
700 500
U analysis tendenciesoverlaid with {u,v} vectors
1000mb 850
700 500
60-90WZonal mean
60-90WZonal mean
60-90WZonal mean
60-90WZonal mean
Analysis tends. on mass and wind fields: fighting the model’s excessive baroclinic vortex
Cyclonic analysis torque:
Anticyclonicanalysis torque
Lower thickness wanted for
thermal wind balance
Lower thickness wanted for
thermal wind balance
Higher thickness wanted
Higher thickness wanted
Analysis tends. on mass and wind fields: fighting model’s excessive baroclinic vortex
Cyclonic analysis torque:
Anticyclonicanalysis torque
Way too much: analysis opposes mean deep convective heating
(with this model’s peculiar characteristic profile)
open contours: model physics heating
GEOS-5 model’s peculiar heating profile in tropical deep convection
Strange cooling spike at 700:
misplaced melting (should
be 550 mb)
Strange cooling spike at 700:
misplaced melting (should
be 550 mb)
dT/dt_mst in TOGA COARE15 day time section at a grid point
largest value on globe: >3 m/s
per day u deceleration by
analysis tendency
(obs fighting model)
largest value on globe: >3 m/s
per day u deceleration by
analysis tendency
(obs fighting model)
warm SST season (later than summer)
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
Thank you
http://www.ncdc.noaa.gov/gibbs/image/GOE-12/WV/2006-07-14-15