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MERRA reanalysis: lessons about process errors in the IASCLIP region

MERRA reanalysis: lessons about process errors in the IASCLIP region. Brian Mapes. NASA’s MERRA reanalysis. “GEOS-5” GCM 1979-present planned (90% completed) ½ x 2/3 degree analysis

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MERRA reanalysis: lessons about process errors in the IASCLIP region

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  1. MERRA reanalysis: lessons about process errors in the IASCLIP region Brian Mapes

  2. NASA’s MERRA reanalysis • “GEOS-5” GCM • 1979-present planned (90% completed) • ½ x 2/3 degree analysis • analysis tendency fields are part of the MERRA dataset: these measure the ways in which the model fields need to be ‘nudged’ to keep the time evolution on track. • Since dynamical tendencies are close to correct (flow and gradients are obs/analyzed), • Analys. Tend. ~ -(phys. Error)

  3. MERRA basic flow: IAS summer

  4. Vertically integrated tendency fields: • Mst = moist physics (conv+LS) (for qv) • Phy = all physics schemes (for theta) • Ana = analysis tendency (~ –phys. error)

  5. Moist physics (conv. + LS) a sink of water vapor

  6. Physical heating pattern quite similar (but also includes radiation, and sensible heating over land)

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

  8. June, July similar: analysis steadily adding qv (physics raining it out too much?)

  9. Vert. int. of analysis tendency of qVery similar pattern in Jun, Jul(A map of radiosonde T biases?)

  10. T tendencies make more sense vertically resolved • T is a structural variable (mass field in geostrophic balance) • Also have analysis tendencies of u,v • Are the analysis increments of T and wind dynamically related?

  11. 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. U analysis tendency: Cyclonic anal. Torque: L ‘wanted’ Low thickness would be ‘wanted’ in thermal wind balance H wanted: Anticyclonic anal. torque High thickness ‘wanted’

  14. T analysis tendency agrees!GCM has too much negative PV at 200mb: anal. damps it too much positive PV at 650mb: anal. damps it Low thickness ‘wanted’ in thermal wind balance High thickness ‘wanted’

  15. “too much” of deep convective heatingwith its peculiar characteristic profile

  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 is re-evap of precip

  17. Remember this? Consistent Analysis is moistening this area, presumably because physics is an excessive sink (raining too much?)

  18. Conclusions • MERRA high-res reanalysis looks good • Analysis tendencies ~ model process errors. • How are routine observations having to nudge this model to keep its state realistic & on track? • IAS summer errors: too much deep convection • seen in excessive PW sink, fought by anal. Tends • also in excessive (fought by analysis) circs. driven by • Too much of model’s deep convective heating • with its hokey Q1 profile  PV error profile ‘fingerprint’ • Could special field obs improve this model? • More than close study of routine/sat obs already allows?

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