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Calibration and correction of LBA/TRMM Abracos pasture site merged dataset.

This document summarizes the meteorological and gas analyzer data collected by the surface site, and the tethered balloon at the Abracos pasture site during the LBA/TRMM/WETAMC campaign, January-February, 1999. The intercomparison and correction of the data is then discussed. Merged datasets for the surface micromet and gas analyzer, and for the surface micromet and tethered balloon have been produced. Several papers have used these data in preliminary form (Betts et al., 2002a,b; Betts and Jakob, 2002; Silva Dias et al., 2002; Williams et al., 2002). The main accomplishment is to reduce the relative mean biases between different humidity measurements [Microclimate, gas analyzer and dew point hygrometer, abbreviated MC, GA and DPH]to about ± 1%. There remain some uncertainties in the absolute calibration of both GA and DPH instruments against a dew point generator reference standard. Consequently, we believe that the absolute calibration accuracy of the humidity data may only be ±1-2% in RH. This is however far superior to the accuracy of conventional RH sensors. An error of ± 1% in RH near noon, corresponds to ±3 hPa in cloud-base, and to slightly less than ±1K in E. This is sufficient to give a corrected dataset, that is extremely valuable for the study of boundary layer and convective processes over Rondônia in the rainy season.

The data archive and the documentation are available at ftp://daac.ornl.gov/data/lba/physical_climate/Betts

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Betts, A. K., J. H. Ball, and J. Fuentes, (2002), Calibration and correction of LBA/TRMM Abracos pasture site merged dataset. [LBABettsDatadoc.pdf] Data set and documents available at ftp://daac.ornl.gov/data/lba/physical_climate/Betts