Intensive Field Campaign 2001 : Preliminary Results in Inter-comparison of the Turbulent Sensors

Abstract

In order to evaluate the difference among the outputs of several turbulent sensors, inter-comparison field campaign was carried out at Terrestrial Environment Research Center(TERC), University of Tsukuba, from the middle of May to the beginning of June, 2001. This period was characterized by growing season of grass and high latent heat exchange. Footprint analysis was performed to evaluate the correspondence between the spatial variation of surface skin temperature and the sensible heat fluxes obtained at the measurement site. The surface skin temperature obtained by an infrared imaging camera together with sensible heat fluxes measured at two points, 3m apart from each other, were used in the analysis. A significant correlation was not found between the surface skin temperatures and the sensible heat fluxes, thus the surface in the upwind direction was assumed to be homogeneous. Comparison was made using standard deviations and covariances of the turbulent variables.
A good agreement was found among all the sonic anemometer-thermometers used here(DA-600, GILL-R3, ATI-SATI). And the fast response hygrometer/CO₂ analyzers(LI-7500 and OP2)got data stably. The errors of LI-7500 and OP2 sensors were reduced by simple recalibration using non-fast response hygrometer(Humicap). Underestimation of flux was occurred only when the correlation coefficient of two sensors' output for the band of dynamic calibration was small.