Panel: C. Fairall, C. Clayson, M. Bourassa, X. Zeng, J. Redelsperger, A. Beljaars, P. Taylor
Moderator: T. Liu
Flux algorithms basically link turbulent fluxes to mean observations
Outstanding issues in bulk algolrithms:
Lack of measurement at high winds, stable conditions has hampered out understanding.
Described the COARE bulk flux algorithm 2.6, and recent modifications that include mesoscale gustiness and modified Charnock constant at higher wind speeds
Questions - Are stability functions over land applicable to ocean? Probably, but they have never been measured over ocean.
Need to test models across the complete parameter space. Particular issues that need more focus:
Bulk algorithms are in pretty good shape for moderate wind speeds and unstable conditions
We have published our work on algorithm development and extensive algorithm intercomparisons. We are currently working on the development of a comprehensive flux algorithm that includes the mesoscale impact of precipitation and clouds at various spatial and temporal scales.
Discussed intercomparison of six algorithms that are widely used in forecasting, reanalysis, and research, and its relevance to generating global ocean surface fluxes.
Discussed Redelsperger's work on gustiness parameterization. Unobserved variability associated with fronts and other mesoscale features give rise to variations in input parameters for bulk models. Also discussed sampling errors due to the unobserved variability, which impacts comparison between models and in situ measurments.
Several Considerations in Modeling Fluxes :
Strong sensitivity to the air-sea flux algorithm has been demonstrated in the ECMWF models in the past. At that time the ECMWF algorithm was rather far away from observations for low as well as high winds. Most current algorithms are rather similar. Remaining issues are: effect of waves, skin temperature, currents and meso-scale variability. Incorporated Webster et al. Diurnal skin sst algorithm, but didn't have a large effect on the model.
Conclusions: ECMWF model has 2 problems: (i) marine boundary layer is too dry (shallow convection and/or boundary layer problem), and (ii) the parametrization and the model lack meso-scale variability.
Questions - ECMWF answer regarding diurnal variability is only one answer, and ECMWF model does not respond strongly to SST anomalies (Webster).
Deficit of energy at small scales which are the ones that SST changes would impact may be reason for this (Rossow).
This parameterization explains why we do not detect changes of Cd10n with age
Curry: We've heard about lots of problems and it seems algorithms may not be biggest problem at this point. What are big problems? High wind, gustiness? What are priorities?
Answer: Depends on where you are in parameter space for starters. The issue that is more important than problems with flux algorithms is what you provide algorithms, measuring specific humidity and wind speed in particular.
Rossow: Should be leery of using what GCM will respond to to define what we go after.
List of Problems: