HR: 0800h
AN: B41B-0203    [Abstracts]
TI: The Contribution of a Virtual Tall Tower to Determine Regional Fluxes
AU: Tolk, L F
EM: lieselotte.tolk@falw.vu.nl
AF: Department of Hydrology and Geo-Environmental Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, Amsterdam, 1081HV Netherlands
AU: Ronda, R J
EM: ronda@knmi.nl
AF: Royal Netherlands Meteorological Institute (KNMI), Postbus 201, De Bilt, 3730AE Netherlands
AU: Meesters, A G
EM: antoon.meesters@falw.vu.nl
AF: Department of Hydrology and Geo-Environmental Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, Amsterdam, 1081HV Netherlands
AU: * Dolman, H
EM: han.dolman@falw.vu.nl
AF: Department of Hydrology and Geo-Environmental Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, Amsterdam, 1081HV Netherlands
AU: Hutjes, R W
EM: ronald.hutjes@wur.nl
AF: Alterra, Wageningen University and Research Center, Postbus 47, Wageningen, 6700AA Netherlands
AU: Elbers, J A
EM: jan.elbers@wur.nl
AF: Alterra, Wageningen University and Research Center, Postbus 47, Wageningen, 6700AA Netherlands
AB: A virtual tall tower experiment has been performed as a part of the CarboEurope Regional Experiment Strategy (CERES) in Les Landes, South West France in the months May and June 2005. CERES aims to produce aggregated regional estimates of the carbon balance and to improve our process understanding of the major controls of CO2 emissions and uptake at the regional scale. A multiple constraint approach is applied, where ground based measurements at several locations are coupled to atmospheric measurements in and above the boundary layer. Near Marmande, located in the central part of the domain, the properties of the boundary layer were measured, both in terms of boundary layer structure and carbon concentration and fluxes. We deployed a 20 m tower, where at 5 heights the air was sampled and analyzed for CO2 and H2O. Soil and sensible heat fluxes and radiation measurements were also performed. Fluxes of water, energy and CO2 were measured using the eddy correlation technique. Additionally, information on the wind profile up to a height of 1800 m was obtained with a SODAR. With a Radio Acoustic Sounding System (RASS) extension, a temperature profile was observed, typically up to a height of 500-700m. Wind velocity and temperature profiles show the development of a stable boundary layer during the night. CO2 respired during the night is trapped in the stable boundary layer; rather large deviations between nocturnal and diurnal CO2 concentrations have been observed. Generally, the variation comprises about 100 ppm, and peak differences of over 200 ppm have been observed in the lower layers. During nighttime the concentrations observed at various heights differ as a result of the structure of the stable boundary layer. The data can be used to obtain the nocturnal respiration rate, provided that horizontal advection is neglected. During daytime CO2 concentrations measured in the lower 20 m are well-mixed. The temperature and wind profiles indicate the height of the mixing layer during the day. The ground based data can be extended with profiles measured by aircrafts. We applied a simple boundary layer model to evaluate the diurnal trend of mixing values of temperature and CO2.
UR: http://www.falw.vu.nl/
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0466 Modeling
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
SC: Biogeosciences [B]
MN: Fall Meeting 2005