PREFACE

    1.1  The Surface Flux Field Problem
    1.2  The Joint WCRP/SCOR  Working Group on Air Sea Fluxes
        1.2.1  Creation of the Working Group
        1.2.2  The remit of the Working Group
        1.2.3  The Working Group's Mode of Working
    1.3  The variables to be considered
    1.4  The flux products assessed
    1.5  Layout of the report

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2 THE REQUIREMENTS FOR SURFACE FLUX DATA SETS.

    2.1  Introduction 
    2.2  NWP systems—assimilation and forecasting
        2.2.1  Introduction 
        2.2.2  The needs of data assimilation systems for flux fields
        2.2.3  The needs of atmospheric forecast models for flux fields   
        2.2.4  Regional observing / nowcasting / forecasting systems
    2.3  Oceanic General Circulation Models  (OGCM's)
        2.3.1  Introduction 
        2.3.2  Parameterisation of the thermal feedback
        2.3.3  Salinity Forcing
        2.3.4  Geophysical consistency of the ocean forcing function
        2.3.5  Forcing fields
        2.3.6  Discussion
        2.3.7  Conclusions
    2.4  Wave Models
    2.5  Sea Ice in Ocean Models and Sea-Ice Modelling
    2.6  Air-Sea Flux Fields and Ocean Data Assimilation
        2.6.1  Introduction
        2.6.2  Ocean Data Assimilation
        2.6.3  Example of Ocean Assimilation requirements - GODAE
    2.7  Evaluation of Climate Models
    2.8  Climate change studies
    2.9  Conclusions

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3 SPACE-TIME VARIABILITY OF THE FLUXES

    3.1  Introduction
    3.2  Synoptic and mesoscale processes
        3.2.1  Mid to High latitude variability
        3.2.2  Variability in the tropics
    3.3  Climate variability
        3.3.1  Introduction
        3.3.2  Detection of climate trends
        3.3.3  Interannual to decadal scale variability
    3.4  Summary

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4 DATA SOURCES FOR FLUXES AND RELATED VARIABLES

    4.1  Introduction
    4.2  in situ data sources
        4.2.1  Voluntary Observing Ships
        4.2.2  Ocean Weather Ships
        4.2.3  Buoys
        4.2.4  Platforms, Rigs, etc
    4.3  Satellite Data Sources
        4.3.1  Introduction
        4.3.2  Non geostationary satellites
        4.3.3  Geostationary satellites
    4.4  NWP and Reanalyses
        4.4.1  Introduction
        4.4.2  Fluxes from operational data assimilation
        4.4.3  Fluxes from reanalyses
    4.5  Residual methods (TOA + model divergences)
    4.6  Ocean Data assimilation
    4.7  Data Sources for Fluxes & Flux-Related Variables over Sea Ice

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5 DIRECT FLUX OBSERVATIONS - STATE OF THE ART

    5.1  Introduction
    5.2  Radiative fluxes
        5.2.1 Introduction
        5.2.2  Shortwave radiation
        5.2.3  Longwave radiation.
    5.3  Turbulent fluxes
        5.3.1  The Eddy correlation method
        5.3.2  The inertial dissipation method
    5.4  Precipitation Flux
        5.4.1  Introduction
        5.4.2  in situ rainfall using Funnel raingauges.
        5.4.3  Other methods of in situ measurement

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6 PARAMETRISATION OF RADIATIVE FLUXES

    6.1  Introduction
    6.2  Radiative fluxes from ship data
        6.2.1  Parameterisation of SW flux
        6.2.2  Parameterisation of LW flux
    6.3  Radiative Transfer Models - RTM’s
        6.3.1  Longwave radiative flux (LW)
        6.3.2  Shortwave radiative flux (SW)
        6.3.3  COARE atmospheric soundings
    6.4  Radiative Fluxes by Remote Sensing
        6.4.1  SW and LW fluxes from TOA radiances
        6.4.2  Longwave Net Flux from a combination of AVHRR and SSM/I
    6.5  Surface Albedo
        6.5.1  Ocean Surface Albedo
        6.5.2  Albedo over sea ice
    6.6  Summary - Parameterisation of Radiative fluxes

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7 PARAMETERISATION OF TURBULENT FLUXES

    7.1  Introduction
    7.2  Example of traditional "Bulk Aerodynamic" formulae
    7.3  Determining the Transfer Coefficients
        7.3.1  Traditional bulk formulae
        7.3.2  New bulk formulae
    7.4  Bulk formulae for light to moderate wind conditions
        7.4.1  The TOGA COARE algorithm
        7.4.2  Other Algorithms
    7.5 Transfers in moderate and high winds
    7.6 Summary of bulk algorithms

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8 RANDOM AND SAMPLING ERRORS IN FLUX FIELDS.

    8.1  Introduction
    8.2  Random errors and sampling density
        8.2.1  Introduction
        8.2.2  Errors and Variability of Monthly Mean Fields
    8.3  Systematic Errors
        8.3.1  Introduction
        8.3.2  Example of a parameterisation error
        8.3.3  Determining errors in VOS reports
        8.3.4  Method of averaging fluxes
        8.3.5 Further discussion
    8.4  Combining Errors
    8.5  Mapping errors
        8.5.1  Introduction
        8.5.2  Successive correction
        8.5.3  Kriging of monthly means and error estimation
    8.6   Sampling problems for satellite-derived quantities
        8.6.1  Introduction
        8.6.2  Sampling errors for precipitation
        8.6.3  Scatterometer Sampling Errors

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9 METHODS OF EVALUATION

    9.1 Introduction
    9.2 Sources of reference data
        9.2.1 Accuracy of research quality measurements: TOGA-COARE
        9.2.2 High quality buoy data
        9.2.3 High-Quality Automated Data from ships
        9.2.4 Data for verification of satellite products
    9.3 Intercomparison of field products
        9.3.1 Comparison to Specialised Products
        9.3.2 Comparison of Variability patterns in flux products
    9.4 Integral constraints
        9.4.1 The global heat and water balance
        9.4.2 Meridional heat and water transport
        9.4.3 Enclosed Seas Used for Flux Validations
        9.4.4 Ocean Mixed Layer Budgets

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10 BASIC VARIABLES - STATE OF THE ART

    10.1  Introduction
    10.2  Sea Surface Temperature (SST)
        10.2.1  Introduction - Definition of Sea Surface temperature
        10.2.2  in situ SST measurements
        10.2.3  Remote sensing of SST
        10.2.4  SST Analyses
    10.3  Sea Surface Salinity (SSS)
        10.3.1  Introduction
        10.3.2  In Situ measurement of SSS
        10.3.3  Remote sensing of SSS
    10.4  Air temperature
        10.4.1  in situ air temperature measurement
        10.4.2  Surface air temperature from the Satellite SSM/I sensor    
    10.5   Humidity
        10.5.1  in situ humidity measurement
        10.5.2  Remote sensing of near surface humidity
    10.6  Wind
        10.6.1 Introduction
        10.6.2  in situ wind data
        10.6.3  Remote sensing of surface wind
    10.7  Waves
    10.8  Cloudiness
        10.8.1 Introduction
        10.8.2 in situ cloud data
        10.8.3 Remote sensing of cloud data
        10.8.4 Combined products
    10.9  Precipitation
        10.9.1 Surface-based  precipitation data
        10.9.2  Precipitation by ocean freshwater budgets
        10.9.3  Satellite Remote sensing of precipitation
        10.9.4   Intercomparison projects
    10.10  River inflow
    10.11  Sea ice
        10.11.1  Sea Ice amount
        10.11.2  Flux-related variables over ice
    10.12  COADS Monthly Summary Trimmed Groups (MSTG) variables.

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11. EVALUATION OF FLUX PRODUCTS

    11.1  Introduction
    11.2  Flux products based on in situ data
        11.2.1  Introduction
        11.2.2  pre-1990 flux studies
        11.2.3  UWM/COADS
        11.2.4  SOC
        11.2.5  IFM
        11.2.6  Comparative assessment
    11.3  Flux products based on Satellite data
        11.3.1  Introduction
        11.3.2  Evaluation of HOAPS
        11.3.3   US Satellite Radiation products
        11.3.4  Japan Surface  Shortwave and Longwave Products
        11.3.5   Residual method
    11.4  Evaluation of the reanalysis products
        11.4.1  Introduction
        11.4.2  Comparisons to in-situ observations
        11.4.3  Polar regions
        11.4.4  Ocean Surface Energy Balance
        11.4.5  Evaporation
        11.4.6  Sensible heat flux
        11.4.7  Net short-wave
        11.4.8  Net long-wave
        11.4.9  Net heat flux
        11.4.10  Evaluating the NCEP1 reanal. by forcing an ocean model
        11.4.11  Winds
        11.4.12  Zonal surface stress
        11.4.13  Meridional surface stress
        11.4.14  Precipitation
        11.4.15  Conclusions
    11.5  Flux Products from Operational NWP model's
    11.6  Evaluation of fluxes in sea-ice covered areas
        11.6.1  Arctic Cloud and surface radiative flux data sets
        11.6.2  Precipitation in the Arctic
        11.6.3  Need for more assessment
    11.7  Evaluation of Waves
        11.7.1 Visual wave observations
        11.7.2 Altimeter wave data
    11.8  Summary

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12. CONCLUSIONS

    12.1. Introduction
    12.2. Summary
    12.3. Meeting the needs
        12.3.1. Budget studies
        12.3.2. Climate variability studies
        12.3.3. Climate models
        12.3.4. Ocean general circulation models
        12.3.5. Wave modelling
        12.3.6. Sea-ice modelling
        12.3.7. NWP and data assimilation
    12.4. Perspectives
    12.5. Specific Recommendations

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ACKNOWLEDGEMENTS

REFERENCES

APPENDIX A. MEMBERS OF THE WORKING GROUP ON AIR-SEA FLUXES

    B.1 Introduction
    B.2 Accessing the Catalogue
    B.3 Preliminary Initial Contents List
    B.4 Information to be submitted

APPENDIX C. ACRONYMS AND ABBREVIATIONS

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