The CHIOTTO tall tower network: its setup and results

Transcription

1 The CHIOTTO tall tower network: its setup and results A.T. Vermeulen*, G. Pieterse, A. Manning, M. Schmidt, L. Haszpra, E. Popa, R. Thompson, J. Moncrieff, A. Lindroth, P. Stefani, J. Morguí, E. Moors, R. Neubert and M. Gloor ECN - Energy research Centre of the Netherlands Westerduinweg 3, 1755 LE Petten, The Netherlands a.vermeulen@ecn.nl Keywords Tall towers, measurements, CO 2, CH 4, SF6, N 2 O The CHIOTTO project aim was to develop a network of 8 tall towers in Europe for measuring continuous and with high precision the concentration of CO 2 and non-co 2 greenhouse gases. In the three years of the project and its extension we succeeded in equipping and making operational all the measurements we envisaged. The tall tower network is now fully integrated into the Atmosphere component of CarboEurope-IP, and now forms a unique and highly innovative part of the Earth System observation network. In this talk the setup of CHIOTTO tall tower network and its results thus far will be presented. RTII6 Oral Presentations 1

2 Regional scale estimation of the land surface carbon balance and representation errors A.J. Dolman, M. van der Molen, L. Tolk and A. Meesters. Vrije Universiteit Department of Hydrology and Geoenvironmental sciences Boelelaan HV Amsterdam the Netherlands Quantification of sources and sinks of carbon at global and regional scales requires a good description of the land sources and sinks of carbon, but also of atmospheric transport, i.e the synoptic and mesoscale meteorology. To bridge the scale gap between global inversions and local scale flux measurements insight is required at the processes responsible for uptake and emission and transport at this intermediate scale. We will show results from a regional experiment performed within CarboEurope-IP illustrating the relevance of atmospheric mesoscale processes for the analysis of flux-profile relations. We will also use a mesoscale model for an area in Siberia to quantify representation errors arising from assumptions of homogeneity at large scales. We do this by studying the effect of increased grid resolution of the model on magnitude of the area averaged fluxes. We show experimental and modeling results from the CarboEurope regional experiment in South West France during May-June 2005 which was performed to determine the variability in concentration gradients and fluxes of CO 2. In the experiment several aircraft were deployed to sample the CO 2 concentration and fluxes over the whole area, while fixed stations observed the fluxes and concentrations at high accuracy. Results show that at regional scale the relation between profiles and fluxes is also not obvious, and is strongly influenced by airmass history and mesoscale flow patterns. Both the results from the modeling study and from the experiment strongly suggest that joint consideration of the synoptic and regional flow, fluxes and land surface is required for a correct interpretation of regional scale fluxes. This calls for an experimental and modeling strategy that takes into account the large spatial gradients in concentrations and the variability in sources and sinks that arise from different land use types and topography. We briefly describe how such an analysis can be performed and evaluate the usefulness for the planning of networks and routine observation sites. RTII7 Oral Presentations 2

3 Mesoscale inversion: first results from the CERES campaign with synthetic data T. Lauvaux(1,2), C. Sarrat(2), M. Uliasz(3), F. Chevallier(1), J. Noilhan(2), P. Bousquet(1), P. J. Rayner(1) Laboratoire des Sciences du Climat et de l'environnement, Centre Nationale des Recherches Météorologiques (1) Laboratoire des Sciences du Climat et de l'environnement, CEA/Saclay, l'orme des Merisiers, Gif-sur-Yvette CEDEX (2) Centre Nationale des Recherches Météorologiques, 42, Avenue Gaspard Coriolis, Toulouse CEDEX (3) Department of Atmospheric Science, Colorado State University, Fort Collins, CO Keywords inversion, mesoscale, carbon, atmospheric transport, biosphere CO 2 flux inversions at large scale traditionally use low-resolution transport models and monthly mean data (Enting et al., 2002, Bousquet et al., 2000). Using mesoscale modelling with a high resolution of atmospheric dynamics and surface fluxes should improve the representation of synoptic variations recorded at continental CO 2 measurement sites, and should better constrain the inversion. But mesoscale inversions on a limited domain face problems of lateral boundary conditions, while the high spatial resolution requires specification of spatial correlations. In this context, we use synthetic data experiments to ascertain the capabilities of such mesoscale inversions. The mesoscale atmosperic model MesoNH was used to simulate the dynamical fields during the 26th and 27th of May 2005, an intensive observation period of the CarboEurope Regional Experiment. A lagrangian particle dispersion model is coupled off-line with the dynamics of MesoNH, in a «backward in time» mode, to estimate the sensitivity of observations to fluxes (Uliasz, 1983). These sensitivities include those to initial conditions and inflow fluxes. Together these constitute an observation operator in the inversion scheme. Finally, a 4dvar scheme was implemented to invert pseudo concentrations. In order to test the method, synthetic data are used in the assimilation scheme, based on ISBA-A-gs modelled fluxes (Calvet et al., 1998). Pseudo concentrations are obtained by the projection of the modelled fluxes by the observation operator, and then perturbed by a random gaussian noise. The results show a strong sensitivity to the setup, and also initial conditions. Reductions of error are limited without introducing spatial correlations in the prior. The improved ability of the transport model allows more intensive use of the data. Regional inversions using mesoscale models appear a promising tool to estimate CO 2 fluxes but they will require good estimates of boundary and initial conditions from global models. RTII8 Oral Presentations 3

4 Atmospheric CO 2 modelling at the regional scale: Application to the CarboEurope Regional Experiment C. Sarrat(1), J. Noilhan, P. Lacarrère, S. Donier (1) Météo France/ CNRM-GAME 42 avenue Coriolis, Toulouse Cedex 1 France The CarboEurope Regional Experiment Strategy (CERES) campaign took place in may and june 2005, in les Landes forest, in the south-west of France (Dolman et al., 2006). This experiment is one of the first which deals with the variations and the budget of atmospheric CO 2 at the regional scale in the frame of the European project CarboEurope. The important field activities included 10 surface fluxes sites installed all over the South-West on representative ecosystems (winter and summer crops, forest, fallow, vineyards ) as well as a 50m tower for high precision CO 2 concentrations measurements of oceanic air masses. Four instrumented aircraft have sampled horizontal and vertical variations of CO 2 within the first 2000 m of the atmosphere. A total of six Intensive Observations Periods (IOP), for 22 days have been triggered on alert according to the meteorological forecasting. These data allow the modeling of atmospheric CO 2 with the meso-scale non-hydrostatic meteorological model Meso-NH (Lafore et al., 1998). This meteorological model is coupled on-line with the surface scheme ISBA-A-gs (Interaction Surface Biosphere Atmosphere, Assimilation, Calvet et al., 1998). The SVAT scheme ISBA-A-gs calculates the surface energy fluxes as well as the surface CO 2 fluxes including carbon assimilation and ecosystem respiration. The surface-atmosphere exchanges take into account not only biospheric CO 2 fluxes but also anthropogenic sources. With this coupled model, Meso-NH / ISBA-A-gs, several days of the CERES camapign, (the 27th of may, 6 of june, 18th of june) are modelled with a grid-nesting configuration at 10 km resolution for the larger domain and 2 km resolution for the small one. These days present ideal condition for CO 2 regional modelling: high insolation, high temperatures, light wind and a strong development of the boundary layer combined with intensive observations, including radio-sounding, aircraft measurement, surface measurements... Moreover, the stage of maturation of the vegetation varies from one day to another and the impact of the atmosphere varies a lot. This presentation shows the results of the simulations: the vertical and horizontal heterogeneity of the CO 2 fluxes and concentrations, the CO 2 budget calculation in the 2 km resolution domain. The simulation results are compared with the observations: surface fluxes over representative ecosystem, energy and CO 2 fluxes measured from aircraft, vertical profiles of CO 2 concentrations from aircrafts measurements including a lagrangian experiment. RTII9 Oral Presentations 4

5 Estimation of CO 2 column concentration from space in the presence of cirrus cloud -Data Analysis of GOSAT Project- Gen Inoue, Tatsuya Yokota*, Nawo Eguchi*, Yukio Yoshida*, Tadao Aoki*, Isamu Morino*, Akiko Higurashi* and Hiroyuki Oguma* Nagoya University *National Institute for Environmental Studies, Japan Furo-cho, Chikusa-ku, Nagoya Japan *16-2 Onogawa, Tsukuba, Ibaraki Japan inouegen@nagoya-u.jp Greenhouse gases Observing SATellite (GOSAT) of Japan is planned to be launched in GOSAT is equipped with an FTS to observe the surface reflected solar radiation to monitor the CO 2 and CH 4 column densities globally. The FTS is capable to observe two shortwavelength infrared bands (1.6 µm and 2.0 µm) which include CO 2 and CH 4 absorption bands, and one visible band at 0.76 µm where the oxygen A-band spectrum exists. Retrieval algorithms to evaluate CO 2 and CH 4 column densities from these bands are now being developed. The retrieval error of column density from the observation data taken under the clear sky condition (cloud and aerosol free condition) is estimated to be about 0.3 %. However the disturbance caused by cirrus cloud is serious, because the frequency of cirrus cloud in the field of view, 10 km in diameter, is significant, and the amount of atmosphere masked by it is large compared with low lying cloud or aerosol. The height of cirrus is estimated from the 0.76 µm band data. The radiation at 1.9 µm (shorter wavelength end of 2.0 µm band) is fully absorbed by water vapor, if the solar light is reflected on a ground surface. But the reflected radiance from cirrus remains because the water vapor above it is very small. By using this signal, the cirrus optical depth can be estimated, and then column densities of CO 2, CH 4 and H2O are retrieved simultaneously with cirrus height, its optical thickness and land surface reflectance. The precision of 0.5 % or better is expected even in the presence of cirrus cloud. The plan of validation of this analysis will be presented, too. RTII10 Oral Presentations 5