Quality Assurance for Eddy Covariance Measurements of Turbulent Fluxes and its Influence on the Energy Balance Closure Problem

Different aspects of the quality assurance and quality control (QA/QC) of micrometeorological measurements were combined to create a comprehensive concept which was then applied to the data from the experiment LITFASS-2003 (Lindenberg Inhomogeneous Terrain – Fluxes between Atmosphere and Surface: a long term Study). The main focus of the QA/QC efforts was on the eddy covariance measurements of the latent heat flux. The results of a turbulence intercomparison experiment showed deviations between the different eddy covariance systems in the order of 15% or less than 30 W m for the latent heat flux and 5% or less than 10 W m for the sensible heat flux. In order to avoid uncertainties due to the post-processing of turbulence data, a comprehensive software package was used for the analysis of whole LITFASS-2003 experiment, including all necessary algorithms for corrections and quality control. An overview of the quality tests results shows that for most of the days more than 80% of the available latent heat flux data are of high quality as long as there are no instrumental problems. The representativeness of a flux value for the target land use type was analysed using a stochastic footprint model. Different methods to calculate soil heat fluxes at the surface are discussed and a sensitivity analysis is conducted to select the most robust method for LITFASS-2003. This QA/QC system has been developed for the requirements of LITFASS-2003 but it can also be applied to other experiments dealing with similar objectives.

[1]  T. Foken,et al.  A modified Bowen ratio method to determine sensible and latent heat fluxes , 2001 .

[2]  W. Oechel,et al.  Energy balance closure at FLUXNET sites , 2002 .

[3]  R. W. Stewart,et al.  Comparison of acoustic instruments in an atmospheric turbulent flow over water , 1971 .

[4]  P. Mason.  Atmospheric boundary layer flows: Their structure and measurement , 1995 .

[5]  J. Kaimal,et al.  Spectral Characteristics of Surface-Layer Turbulence , 1972 .

[6]  T. Foken,et al.  On the determination of dry deposition and emission of gaseous compounds at the biosphere-atmosphere interface;Bestimmung der trockenen Deposition von Gasbeimengungen an der Grenzfläche Biosphäre-Atmosphäre , 1995 .

[7]  B. Hicks,et al.  A comparison of turbulence measurements by different instruments; Tsimlyansk field experiment 1970 , 1973 .

[8]  R. McMillen,et al.  An eddy correlation technique with extended applicability to non-simple terrain , 1988 .

[9]  C. B. Tanner,et al.  Error analysis of bowen ratios measured by differential psychrometry , 1970 .

[10]  V. Moron,et al.  West African Monsoon Dynamics and Eastern Equatorial Atlantic and Pacific SST Anomalies (1970-88) , 1998 .

[11]  E. M. Blyth,et al.  Application of aggregation models to surface heat flux from the Sahelian tiger bush , 1995 .

[12]  A. J. Dyer,et al.  Flow distortion by supporting structures , 1981 .

[13]  J.-P. Goutorbe,et al.  HAPEX-Sahel: a large-scale study of land-atmosphere interactions in the semi-arid tropics , 1994 .

[14]  K. E. Moore,et al.  Importance of Low-Frequency Contributions to Eddy Fluxes Observed over Rough Surfaces , 2001 .

[15]  Jørgen Højstrup,et al.  A simple model for the adjustment of velocity spectra in unstable conditions downstream of an abrupt change in roughness and heat flux , 1981 .

[16]  J. G. Lockwood,et al.  Tropical climatology , 1978, Nature.

[17]  F. Wimmer,et al.  Some aspects of the energy balance closure problem , 2006 .

[18]  R. R. Brook.  The influence of water vapor fluctuations on turbulent fluxes , 1978 .

[19]  B. A. Kader,et al.  International turbulence comparison experiment (ITCE-81) , 1985 .

[20]  T. Foken,et al.  The energy balance closure problem , 2004 .

[21]  Thomas Foken,et al.  Processing and quality control of flux data during LITFASS-2003 , 2006 .

[22]  Thomas Foken,et al.  On the Significance of the Webb Correction to Fluxes , 2003 .

[23]  H. D. Bruin,et al.  Oxygen Sensitivity of Krypton and Lyman-α Hygrometers , 2003 .

[24]  William J. Massman,et al.  Handbook of micrometeorology : a guide for surface flux measurement and analysis , 2004 .

[25]  J. Wyngaard,et al.  How Close is Close Enough When Measuring Scalar Fluxes with Displaced Sensors , 1997 .

[26]  H. Mengelkamp,et al.  Evaporation over a Heterogeneous Land Surface: EVA_GRIPS and the LITFASS-2003 Experiment—An Overview , 2006 .

[27]  Thomas Foken,et al.  New Equations For Sonic Temperature Variance And Buoyancy Heat Flux With An Omnidirectional Sonic Anemometer , 2001 .

[28]  Inhomogeneity of the Land Surface and Problems in theParameterization of Surface Fluxes in Natural Conditions , 1998 .

[29]  T. Foken,et al.  A Study of the Internal Boundary Layer due to a Roughness Change in Neutral Conditions Observed During the LINEX Field Campaigns , 1999 .

[30]  J. A. Businger,et al.  Evaluation of the Accuracy with Which Dry Deposition Can Be Measured with Current Micrometeorological Techniques. , 1987 .

[31]  W. J. Massmana,et al.  Eddy covariance flux corrections and uncertainties in long-term studies of carbon and energy exchanges , 2002 .

[32]  Eric F. Lambin,et al.  The Sahelian Climate , 2004 .

[33]  J. Wallace,et al.  Soil evaporation from tiger-bush in south-west Niger , 1997 .

[34]  B. Fontaine,et al.  Spring to summer changes in the West African monsoon through NCEP/NCAR reanalyses (1968–1998) , 2002 .

[35]  R. Stull.  An Introduction to Boundary Layer Meteorology , 1988 .

[36]  E. Swiatek,et al.  Density Fluctuations and Use of the Krypton Hygrometer in Surface Flux Measurements , 1993 .

[37]  John C. Wyngaard,et al.  Transducer-Shadow Effects on Turbulence Spectra Measured by Sonic Anemometers , 1985 .

[38]  A. Dolman,et al.  Sonic anemometer (co)sine response and flux measurement I. The potential for (co)sine error to affect sonic anemometer-based flux measurements , 2003 .

[39]  Energy and water budgets of an area of patterned woodland in the Sahel , 1993 .

[40]  S. Wofsy,et al.  Physiological responses of a black spruce forest to weather , 1997 .

[41]  Yadvinder Malhi,et al.  A Re-Evaluation of Long-Term Flux Measurement Techniques Part I: Averaging and Coordinate Rotation , 2003 .

[42]  I. S. Bowen.  The Ratio of Heat Losses by Conduction and by Evaporation from any Water Surface , 1926 .

[43]  T. Foken,et al.  Tools for quality assessment of surface-based flux measurements , 1996 .

[44]  Thomas Foken,et al.  Post-Field Data Quality Control , 2004 .

[45]  T. Foken,et al.  The Lehstenbach and Steinkreuz catchments in NE Bavaria, Germany , 2004 .

[46]  W. Oechel,et al.  FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities , 2001 .

[47]  Walter Senn,et al.  A cospectral correction model for measurement of turbulent NO2 flux , 1995 .

[48]  E. F. Bradley,et al.  An international turbulence comparison experiment (ITCE 1976) , 1982 .

[49]  J. Kaimal,et al.  Minimizing flow distortion errors in a sonic anemometer , 1990 .

[50]  S. P. S. Arya,et al.  Introduction to micrometeorology , 1988 .

[51]  C. J. Moore.  Frequency response corrections for eddy correlation systems , 1986 .

[52]  Dean Vickers,et al.  Quality Control and Flux Sampling Problems for Tower and Aircraft Data , 1997 .

[53]  Carl A. Friehe,et al.  Flux Corrections Revisited , 2002 .

[54]  Ü. Rannik,et al.  Estimates of the annual net carbon and water exchange of forests: the EUROFLUX methodology , 2000 .

[55]  A. Smedman,et al.  Accuracy of Sonic Anemometers: Laminar Wind-Tunnel Calibrations Compared to Atmospheric In Situ Calibrations Against a Reference Instrument , 2004 .

[56]  E. Batchvarova,et al.  Experimental determination of turbulent fluxes over the heterogeneous LITFASS area: Selected results from the LITFASS-98 experiment , 2002 .

[57]  Thomas Foken,et al.  Angewandte Meteorologie : mikrometeorologische Methoden , 2003 .

[58]  J. Finnigan,et al.  A Re-Evaluation of Long-Term Flux Measurement Techniques Part II: Coordinate Systems , 2004 .

[59]  Yann Kerr,et al.  An overview of HAPEX-Sahel: a study in climate and desertification. , 1997 .

[60]  Thomas Foken,et al.  Workshop on Instrumental and Methodical Problems of Land Surface Flux Measurements , 1995 .

[61]  Bert G. Heusinkveld,et al.  Surface energy balance closure in an arid region: role of soil heat flux , 2004 .

[62]  Ray Leuning,et al.  Measurements of Trace Gas Fluxes in the Atmosphere Using Eddy Covariance: WPL Corrections Revisited , 2004 .

[63]  Heping Liu.  An Alternative Approach for CO2 Flux Correction Caused by Heat and Water Vapour Transfer , 2005 .

[64]  Monique Y. Leclerc,et al.  Footprint prediction of scalar fluxes using a Markovian analysis , 1990 .

[65]  J. Wilczak,et al.  Sonic Anemometer Tilt Correction Algorithms , 2001 .

[66]  T. W. Horst.  On Frequency Response Corrections for Eddy Covariance Flux Measurements , 2000 .

[67]  Eric A. Smith,et al.  Surface flux measurements in FIFE: An overview , 1992 .

[68]  A. Verhoef,et al.  A system to measure surface fluxes of momentum, sensible heat, water vapour and carbon dioxide , 1997 .

[69]  Mechanisms by Which Surface Drying Perturbs Tropical Precipitation Fields , 1994 .

[70]  D. Lenschow,et al.  The characteristics of turbulent velocity components in the surface layer under convective conditions , 1977 .

[71]  W. Massman,et al.  Uncertainty in Eddy Covariance Flux Estimates Resulting from Spectral Attenuation , 2004 .

[72]  Pierre Camberlin,et al.  Seasonality and atmospheric dynamics of the teleconnection between African rainfall and tropical sea‐surface temperature: Atlantic vs. ENSO , 2001 .

[73]  J. Wyngaard,et al.  The Effects of Probe-Induced Flow Distortion on Atmospheric Turbulence Measurements , 1981 .

[74]  Response Characteristics of the U.W. Sonic Anemometer , 1986 .

[75]  E. K. Webb,et al.  Correction of flux measurements for density effects due to heat and water vapour transfer , 1980 .

[76]  J. C. Kaimal,et al.  A Continuous Wave Sonic Anemometer-Thermometer , 1963 .

[77]  Atsumu Ohmura,et al.  Objective Criteria for Rejecting Data for Bowen Ratio Flux Calculations , 1982 .

[78]  A. Dolman,et al.  Evaporation, sensible heat and canopy conductance of fallow savannah and patterned woodland in the Sahel , 1997 .

[79]  Thomas Foken,et al.  Sensitivity analysis for two ground heat flux calculation approaches , 2005 .

[80]  The Effect of Atmospheric Stability on the Surface-Layer Characteristics in a Low-Wind Area of Tropical West Africa , 1997 .

[81]  J. Højstrup.  A statistical data screening procedure , 1993 .

[82]  Thomas Foken,et al.  The energy balance experiment EBEX-2000 , 2002 .

[83]  J. Adedokun.  West African precipitation and dominant atmospheric mechanisms , 1978 .

[84]  C. Bernhofer,et al.  The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance , 2007 .

[85]  T. W. Horst,et al.  Footprint estimation for scalar flux measurements in the atmospheric surface layer , 1992 .

[86]  Frans T. M. Nieuwstadt,et al.  Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes , 1983 .

[87]  Siegfried Raasch,et al.  LES Study of the Energy Imbalance Problem with Eddy Covariance Fluxes , 2004 .

[88]  M. Molen,et al.  Sonic anemometer (co)sine response and flux measurement: II. The effect of introducing an angle of attack dependent calibration , 2004 .

[89]  Elizabeth Pattey,et al.  Scaling up flux measurements for the boreal forest using aircraft‐tower combinations , 1997 .

[90]  K. Bernhardt,et al.  Zum Einfluss der turbulenzbedingten Dichteschwankungen auf die Bestimmung turbulenter Austauschströme in der Bodenschicht , 1988 .

[91]  E. K. Webb.  On the correction of flux measurements for effects of heat and water vapour transfer , 1982 .

[92]  T. Foken,et al.  Verdunstung über einer heterogenen Landoberfläche - das Litfass-2003-Experiment : ein Bericht , 2004 .