Atmospheric Measurement Techniques www.atmos-meas-tech.net 1867-1381 1867-8548 2 2 2009 10.5194/amt-2-741-2009 http://www.atmos-meas-tech.net/2/741/2009/ http://www.atmos-meas-tech.net/2/741/2009/amt-2-741-2009.html http://www.atmos-meas-tech.net/2/741/2009/amt-2-741-2009.pdf 741 753 2009-11-18 Uncertainty analysis of computational methods for deriving sensible heat flux values from scintillometer measurements P. A. Solignac pasolignac@gmail.com A. Brut J.-L. Selves J.-P. Béteille J.-P. Gastellu-Etchegorry P. Keravec P. Béziat E. Ceschia CESBIO, 18, avenue Edouard Belin, bpi 2801, 31401 Toulouse Cedex 9, France The use of scintillometers to determine sensible heat fluxes is now common in studies of land-atmosphere interactions. The main interest in these instruments is due to their ability to quantify energy distributions at the landscape scale, as they can calculate sensible heat flux values over long distances, in contrast to Eddy Covariance systems. However, scintillometer data do not provide a direct measure of sensible heat flux, but require additional data, such as the Bowen ratio (<i>β</i>), to provide flux values. The Bowen ratio can either be measured using Eddy Covariance systems or derived from the energy balance closure. In this work, specific requirements for estimating energy fluxes using a scintillometer were analyzed, as well as the accuracy of two flux calculation methods. We first focused on the classical method (used in standard softwares) and we analysed the impact of the Bowen ratio on flux value and uncertainty. For instance, an averaged Bowen ratio (<i>β</i>) of less than 1 proved to be a significant source of measurement uncertainty. An alternative method, called the "<i>β</i>-closure method", for which the Bowen ratio measurement is not necessary, was also tested. In this case, it was observed that even for low <i>β</i> values, flux uncertainties were reduced and scintillometer data were well correlated with the Eddy Covariance results. Besides, both methods should tend to the same results, but the second one slightly underestimates <i>H</i> while <i>β</i> decreases (<5%). Andreas, E. L.: Estimating Cn² over Snow and Sea Ice from Meteorological Data, J. Opt. Soc. Am., 5, 481–495, 1988. Andreas, E.L.: Two-wavelength method of measuring path-averaged turbulent surface heat fluxes, J. Atmos. And Ocean Tech., 6, 280-292, 1989. Asanuma, J. and Lemoto, K.: Measurements of regional sensible heat flux over Mongolian grassland using large aperture scintillometer, J. Hydrol., 333, 58–67, 2007. Aubinet, M., Grelle, A., Ibrom, A., Rannik, Ü., Moncrieff, J., Foken, T., Kowalski, A. S., Martin, P. H., Berbigier, P., Bernhofer, C., Clement, R., Elbers, J., Granier, A., Grünwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snijders, W., Valentini, R., and Vesala, T.: Estimates of the annual net carbon and water exchange of forests: The EUROFLUX methodology, Adv. Ecol. Res., 30, 113–175, 2000. Aubinet, M., Clement, R., Elbers, J., Foken, T., Grelle, A., Ibrom, A., Moncrieff, H., Pi-legaard, K., Rannik, U., and Rebmann, C. : Methodology for data acquisition, storage and treatment, in: Fluxes of carbon, water and energy of European forests. Ecological Studies, edited by: Valentini, R., 163, Springer, Berlin, Heidelberg, 9–35, 2003. Bastiaanssen, W. G. M., Menenti, M., Feddes, R. A., and Holtslag, A. A. M.: A Remote Sensing Surface Energy Balance Algorithm for Land (SEBAL) – 1. Formulation, J. Hydrol., 212–213, 198–212, 1998. Billesbach, D. P., Fischer, M. L., Torn , M. S., and Berry, J. A.: A portable eddy covariance system for the measurement of Ecosystem-Atmosphere exchange of CO₂, Water Vapor, and Energy, J. Atmos. Oceanic. Technol., 21, 684–695, 2004. Bowen, I. S.: The ratio of heat losses by conduction and by evaporation from any water surface, Phys. Rev., 27, 779–787, 1926. Brotzge, J. A.: Closures of the surface energy budget, PhD Thesis, The Univeristy of Oklahoma, March 2001, 208~pp., 2001. Businger, J. A., Miyake, M., Dyer, A. J., and Bradley, E. F.: On the direct determination of heat flux near the ground, J. Appl. Meteor., 6, 1025–1031, 1967. Dabberdt, W. F., Lenschow, D. H., Horst, T. W., Zimmerman, P. R., Oncley, S. P. and Delany, A. C.: Atmosphere-surface exchange measurements, Science, 260, 1472–1481, 1993. Da Rocha, H.R.,~Goulden, M. L.,~Miller, S. D.,~Menton M. C.,~Pinto, L. D. V. O., de Freitas, H. C., and Silva Figueira, A. M.: Seasonality of water and heat fluxes over a tropical forest in eastern amazonia, Ecol. Appl., 14, No sp4, 22–32, 2004. De Bruin, H. A. R, Kohsiek,W., van den Hurk, B. J. M.: A verification of some methods to determine the fluxes of momentum, sensible heat, and water vapor using standard deviation and structure parameter of scalar meteorological quantities, Bound.-Lay. Meteorol., 63, 231–257, 1993. De Bruin, H. A. R., Van den Hurk, B. J. J. M., and Kohsiek, W.: Ths Scintillation Method tested over a dry vineyard area, Bound.-Lay. Meteorol., 76, 25–40, 1995. Dugas, W. A., Fritschen, L. J., Gay, L. W., Held, A. A., Matthias, A. D., Reicosky, D. C., Steduto, P. and Steiner, J. L.: Bowen ratio, eddy correlation, and portable chamber measurements of sensible and latent heat flux over irrigated spring wheat, Agric. For. Meteorol., 56, 1–20, 1991. Foken, T.: The energy balance closure problem – An overview, Ecol. Appl., 18, 1351–1367, 2008. Green, A. E. and Ayashi, Y.: Using the scintillometer over a rice paddy, Japan, J. Agric. Meteorol., 54, 225–231, 1998. Gu, J., Smith, E. A., and Merritt, J. D.: Testing Energy Balance Closure with GOES retrieved Net Radiation and in Situ Measured Eddy Correlation Fluxes in BOREAS, J. Geophys. Res., 104, 27–81, 1999. Halldin, S. and Lindroth, A.: Errors in net radiometry: comparison and evaluation of six radiometer designs, J. Atmos. Oceanic. Technol., 9, 762–783, 1992. Hartogensis, O. K., Watts, C. J., Rodriguez, J.-C., de Bruin, H. A. R.: Derivation of the effective height for scintillometers: La Poza experiment in Northwest Mexico, J. Hydrol., 4, 915–928, 2003. Hill, R. J., Clifford, S. F. and Lawrence, R. S.: Refractive index and absorption fluctuations in the infrared caused by temperature, humidity and pressure fluctuations, J. Opt. Soc. Am., 70, 1192–1205, 1980. Hill, R. J.: Implications of Monin-Obukhov Similarity Theory for Scalar Quantities, J. of Atm. Sci., 46, No.14, 1989. Hill, R. J., Ochs, G. R., and Wilson, J. J.: Measuring Surface Layer Fluxes of Heat and Momentum Using Optical Scintillation, Boundary-Layer Meteorol., 58, 391–408, 1992. Hoedjes, J. C. B., Zuurbier, R. M. and Watts, J. C.: Large aperture scintillometer used over a homogeneous irrigated area, partly affected by advection, Bound.-Lay. Meteorol., 105, 99–117, 2002. Hoedjes, J. C. B., Chehbouni, A., Ezzahar, J., Escadafal, R., and De Bruin, H. A. R.: Comparison of Large Aperture Scintillometer and Eddy Covariance Measurements: Can Thermal Infrared Data be Used to Capture Footprint Induced Differences?, J. Hydrometeorol., 8 (\refeq2), 144–159, 2007. Horst, T. W. and Weil, J. C.: How far is far enough? The fetch requirements for micrometeorological measurement of surface fluxes, J. Atm. Oc. Tech., 11, 1018–1025, 1994. Kleissl, J., Gomez, J., Hong, S.-H., Hendrickx, J. M. H, Rahn, T., and Defoor, W. L.: Large Aperture Scintillometer Intercomparison Study, Bound.-Lay. Meteorol., 128, 133–150, 2008. Kohsiek, W., Meijninger, W. M. L., deBrui, H. A. R., and Beyrich, F.: Saturation of the large aperture scintillometer, Boundary-Lay. Meteorol., 121, 111–126, 2006. Kohsiek, W., Liebethal, C., Foken, T., Vogt, R., Oncley, S. P., Bernhofer, C., de Bruin, H. A. R.: The energy balance experiment EBEX-2000, Part III : Behaviour and quality of radiation measurements, Boundary-Lay. Meteorol., 123, 55–75, 2007. Konzelmann, T., Calanca, P., Muller, G., Menzel, L., and Lang, H.: Energy balance and evapotranspiration in a high mountain area during summer, J. Appl. Meteorol., 36, 7, 966–973, 1997. Lamaud, E., Ogée, J., Brunet, Y., and Berbigier, P.: Validation of Eddy flux measurements above the Understorey of a Pine Forest, Agr. Forest. Meteorol., 106, 187–203, 2001. Lee, X., Massman, W. J., and Law, B.: Handbook of Micrometeorology: A Guide for Surface Flux Measurement and Analysis, Kluwer, Dordrecht, The Netherlands, 250~pp., 2004. Marx, A., Kunstmann, H., Schuttemeyer, D. and Moene, A. F.: Uncertainty analysis for satellite derived sensible heat fluxes and scintillometer measurements over Savannah environment and comparison to mesoscale meteorological simulation results, Agr. Forest. Meteorol., 148, 656–667, 2008. McAneney, K. J., Green, A. E., and Astill, M. S.: Large-Aperture scintillometry: the homogeneous case, Agric. For. Meteorol., 76, 149–162, 1995. Meijninger, W. M. L. and de Bruin, H. A. R.: The sensible heat fluxes over irrigated ares in western Turkey determined with a large aperture scintillometer, J. Hydrol., 229, 42–49, 2000. Meijninger, W. M. L., Hartogensis, O. K., Kohsiek, W., Hoedjes, J. C. B., Zuurbier, R. M., and De Bruin, H. A. R.: Determination of Area-Averaged Sensible Heat Fluxes with a LargeAperture Scintillometer over a Heterogeneous Surface – Flevoland Field Experiment, Bound.-Lay. Meteorol., 105, 37–62, 2002a. Meijninger, W. M. L., Green, A. E., Hartogensis, O. K., Kohsiek, W., Hoedjes, J. C. B., Zuurbier, R. M. and De Bruin, H. A. R.: Determination of area-averaged water vapour fluxes with large aperture and radio wave scintillometers over heterogeneous surface-Flevoland field experiment, Bound.-Lay. Meteorol., 105, 63–83, 2002b. Meijninger, W. M. L., Beyrich, F., Kohsiek, W., Bruin, H. A. R., and de Lüdi, A.: Scintillometer fluxes of sensible and latent heat over a heterogeneous area – a contribution to LITFASS-2003, 16th Symposium on Boundary Layers and Turbulence, 9–13 August 2004, Portland, Maine, Boston, USA: American Meteorological Society, 9.2, 2004. Moene, A. F.: Effects of water vapour on the structure parameter of the refractive index for near-infrared radiation, Boundary-Layer Meteorol., 107, 635–653, 2003. Nie, D., Kanemasu, E. T., Fritschen, L. J., Weaver, H. L., Smith, E. A., Verma, S. B., Field, R. T., Kustas, W. P., and Stewart, J. B.: An intercomparison of surface energy flux measurement systems used during FIFE 1987, J. Geophys. Res., 97, 18715–18724, 1992. Ochs, G. R. and Wilson, J. J.: A second-Generation Large-Aperture Scintillometer, NOAA Tech. Memo., ERL WPL-232, Env. Res. Lab, Boulder, CO, 24~pp., 1993. Panofsky, H. A and Dutton, J. A.: Atmospherric Turbulence: Models and Methods for Engineering Applications, J. Wiley, New York, USA, 397~pp., 1984. Paulson, C. A. : The mathematical representation of wind speed and temperature profiles in the unstable atmospheric surface layer, J. Appl. Meteorol., 9, 857–861, 1970. Sadhuram Y., Ramana Murthy, T. V., Sarma, Y. V. B., and Murthy, V. S. N.: Comments on On the estimation of overwater Bowen ratio from sea – air temperature difference., J. Phys. Oceanogr., 31, 1933–1934, 2001. Sorbjan, Z.: Notes and Correspondaence~: Monin-Obukhov Similarity for Refractive Index Revisited, J. Atmos. Sci., 50, 21, 3677–3679, 1993. Twine, T. E., Kustas, W. P., Norman, J. M., Cook, D. R, Houser, P. R., Meyers, T. P., Prueger, J. H., Starks, P. J. and Wesely, M. L.: Correcting Eddy-Covariance Flux Underestimates over a Grassland, Agr. Forest. Meteorol., 103, 279–300, 2000. Von Randow, C., Kruijt, B., Holtslag, A. A. M., de Oliveira, M. B. L.: Exploring eddy-covariance and large-aperture scintillometer measurements in an Amazonian rain forest, Agr. Forest. Meteorol., 148, 680–690, 2008. Wang, T., Ochs, G., and Clifford, S.: Saturation-Resistant optical scintillometer to measure Cn², J. Opt. Soc. Am., 68, 334–338, 1978. Webb, E. K. Pearman, G. I., and Leuning, R.: Correction of flux measurements for density effects due to heat and water vapor transfer, Q. J. Roy. Meteor. Soc., 106, 85–100, 1980. Wesely, M. L.: The combined effect of Temperature and humidity Fluctuations on Refractive index, J. Appl. Meteorol., 15, 43–49, 1976. Wyngaard, J. C., Izumi, Y., and Collins Jr., S. A.: Behavior of the Refractive Index Structure Parameter near the Ground, J. Opt. Soc. Amer., 61, 1646–1650, 1971.