My Agenda for CFS Diagnostics Ancient Chinese proverb: “ Even a 9-month forecast begins with a single time step.” --Hua-Lu Pan.
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Presentation on theme: "My Agenda for CFS Diagnostics Ancient Chinese proverb: “ Even a 9-month forecast begins with a single time step.” --Hua-Lu Pan."— Presentation transcript:
My Agenda for CFS Diagnostics Glenn.White@noaa.gov Ancient Chinese proverb: “ Even a 9-month forecast begins with a single time step.” --Hua-Lu Pan
IMHO --diagnostics of hind-casts and AMIP/CMIP integrations complicated --no atmospheric reanalysis consistent with CFS --significant uncertainties in air-sea fluxes --single global forecast model for weather and seasonal forecasts --operational weather forecasts give larger sample of performance of atmospheric model --should examine carefully short-range CFS forecasts --more insight into model problems from 1-day forecasts than from seasonal forecasts or AMIP/CMIP integrations
Hypothesis-- Over last 10 years considerable effort at EMC in improving tropical analyses and short-range forecasts has produced good atmospheric model for seasonal forecasts of equatorial Pacific SST. Better hurricanes Better ENSO Moral-- Don’t separate weather and climate.
“Error” in transient eddy kinetic energy in 64 level AMIP run of GFS Sep. 01- Mar.02 1979-2001
Difference in analyzed transient eddy kinetic energy Sep.01 –Mar.02 GDAS minus NCEP1
NCEP1—T62, 28 levels NESDIS temperature retrievals GDAS—T170, 42 levels Radiances used
Transient eddies in AMIP runs cannot be verified in the Southern Hemisphere; error in AMIP transient eddies appears to be less than error in NCEP1 reanalysis.
Verifying AMIP runs of the current GFS model against NCEP1 reanalysis can be inappropriate, even for atmospheric fields. Need to compare CDAS to GDAS to see if differences between CDAS and GDAS are insignificant compared to differences between AMIP and CDAS. Need periodic reanalyses with the operational CFS for consistent verification of seasonal forecasts.
GODAS (MOM V.3) Forced by wind stress, heat flux, precipitation- evaporation SST is relaxed to weekly NCEP SST analysis surface salinity is relaxed to Levitus monthly SSS climatology. Wind stress is thought to have most impact
OGCM MOM Global v.3 Data Assimilation 3D VAR Observations: XBTs TAO P-Floats Altimetry Analyzed Fields: Temperature Salinity Ocean Data Assimilation System (ODAS) Surface Stress Heat Flux P-E From ?
-- NCEP-2 reanalysis 1979-present (CDAS-2)T62, 28 levels Used in hind-casts not consistent with CFS What are best air-sea fluxes to initialize ocean assimilation for real-time forecasts?
--GDAS T254, 64 levels better data assimilation and atmospheric model than NCEP-2 better fluxes?? Not used in hind-casts More consistent with CFS than NCEP2
NCEP2 too many easterly waves (Hodges et al., J Clim)
Normalized RMS difference of monthly mean stress over 3 years Normalized bias in 3-year mean stress magnitude GDAS vs. CDAS
Nino 3.4 5S-5N 190-240E Equatorial east Pacific
CONCLUSIONS --GDAS, ERA40 surface stresses agree more with independent estimates than NCEP2, implying progress --disagreement between different estimates in equatorial Pacific implies substantial uncertainty in surface stress --NCEP2 too many easterly waves in Pacific --surface heat flux global balance in NCEP2, not GDAS --GDAS too much sfc NSW; clouds, moisture need work --GDAS better patterns of sfc NSW, NHF --GDAS better precipitation pattern than NCEP2
New CFS will use fluxes from NCEP-2 reanalysis to force ocean data assimilation, for consistency with hind-casts Future CFS will conduct reanalyses with new CFS models for consistency of system as well as consistency with hind-casts. (If $$) New CFS every 3-5 years. New global reanalyses 1979 to present every 3-5 years in support of seasonal forecasting.
Climate drift in SST in 23 year coupled runs Climate drift with 28 levels Climate drift with 64 levels Much less drift along equator with 64 levels
1)Increased Ekman pumping and more upwelling at equator in Pacific with 28 than with 64 levels, probably associated with stronger Pacific ITCZ with 28 levels; doesn’t explain warmer tropical SST in Atlantic 2) Lack of marine stratus with 64 levels compared to 28 levels; more short wave in eastern oceans, possibly warming SST which are advected to equator.