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See detailOptimized approach to retrieve information on the tropospheric and stratospheric carbonyl sulfide (OCS) vertical distributions above Jungfraujoch from high-resolution FTIR solar spectra
Lejeune, Bernard ULg; Mahieu, Emmanuel ULg; Servais, Christian ULg et al

in Geophysical Research Abstracts (2010), 12(EGU2010-3513),

Carbonyl sulfide (OCS), which is produced in the troposphere from both biogenic and anthropogenic sources, is the most abundant gaseous sulfur species in the unpolluted atmosphere. Due to its low chemical ... [more ▼]

Carbonyl sulfide (OCS), which is produced in the troposphere from both biogenic and anthropogenic sources, is the most abundant gaseous sulfur species in the unpolluted atmosphere. Due to its low chemical reactivity and water solubility, a significant fraction of OCS is able to reach the stratosphere where it is converted to SO2 and ultimately to H2SO4 aerosols (Junge layer). These aerosols have the potential to amplify stratospheric ozone destruction on a global scale and may influence Earth’s radiation budget and climate through increasing solar scattering. The transport of OCS from troposphere to stratosphere is thought to be the primary mechanism by which the Junge layer is sustained during nonvolcanic periods. Because of this, long-term trends in atmospheric OCS concentration, not only in the troposphere but also in the stratosphere, are of great interest. A new approach has been developed and optimized to retrieve atmospheric abundance of OCS from high-resolution ground-based infrared solar spectra by using the SFIT-2 (v3.91) algorithm, including a new model for solar lines simulation (solar lines often produce significant interferences in the OCS microwindows). The strongest lines of the nu3 fundamental band of OCS at 2062 cm-1 have been systematically evaluated with objective criteria to select a new set of microwindows, assuming the HITRAN 2004 spectroscopic parameters with an increase in the OCS line intensities of the nu3band main isotopologue 16O12C32S by 15.79% as compared to HITRAN 2000 (Rothman et al., 2008, and references therein). Two regularization schemes have further been compared (deducted from ATMOS and ACE-FTS measurements or based on a Tikhonov approach), in order to select the one which optimizes the information content while minimizing the error budget. The selected approach has allowed us to determine updated OCS long-term trend from 1988 to 2009 in both the troposphere and the stratosphere, using spectra recorded on a regular basis with Fourier Transform Infrared spectrometers (FTIRs), under clear-sky conditions, at the NDACC site (Network for the Detection of Atmospheric Composition Change, visit http://www.ndacc.org) of the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580m asl). Trends and seasonal cycles deduced from our results will be compared to values published in the literature and critically discussed. In particular, we will confirm the recent change in the OCS total column trend, which has become positive since 2002 before undergoing a slowing down over the last years. [less ▲]

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See detailTrends of CO2, CH4 and N2O over 1985-2010 from high-resolution FTIR solar observations at the Jungfraujoch station
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Geophysical Research Abstracts (2010), 12(EGU2010-15418-2),

Two state-of-the-art Fourier Transform Infrared (FTIR) spectrometers are operated at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580m asl) within the framework of the Network for the Detection of ... [more ▼]

Two state-of-the-art Fourier Transform Infrared (FTIR) spectrometers are operated at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580m asl) within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). The earliest FTIR observations have been obtained there in 1984. Since then, regular recordings of high-resolution solar absorption spectra have been performed at that site, under clear-sky conditions, allowing to collect almost 29000 observations relevant to the present communication. We present time series of three greenhouse gases targeted by the Kyoto Protocol: CO2, CH4 (and its isotopologue 13CH4) and N2O. These data sets have been obtained with the SFIT-2 algorithm which implements the Optimal Estimation Method of Rodgers (1990). This allows retrieving total columns of the target gases as well as information on their distribution with altitude. For the methane isotopologues and N2O, a Tikhonov L1 regularization scheme has been applied, as part of an harmonization effort carried out within the European HYMN project (see also Dils et al, 2010; Foster et al., 2010). Trends –and their associated uncertainties– characterizing these long series as well as the seasonal modulations have been determined with a statistical tool using bootstrap resampling (Gardiner et al., 2008). Trend values will be presented and critically discussed; in particular, we will investigate if significant changes in the rate of accumulations of these four atmospheric gases occurred over the last 25 years. Numerous additional greenhouse gases are accessible to the FTIR technique. Examples of such trend studies are reported at the EGU General Assembly by Mahieu et al. (2010) and Rinsland et al. (2010). [less ▲]

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See detailRecent trends of inorganic chlorine and halogenated source gases above the Jungfraujoch and Kitt Peak stations derived from high-resolution FTIR solar observations
Mahieu, Emmanuel ULg; Rinsland, Curtis P.; Gardiner, Tom et al

in Geophysical Research Abstracts (2010), 12(EGU2010-2420-3),

The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5ºN and 30.9ºN ... [more ▼]

The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5ºN and 30.9ºN, respectively. State-of-the-art interferometers are operated at these sites within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). These instruments allow to record spectra on a regular basis, under clear-sky conditions, using a suite of optical filters which altogether cover the 2 to 16 micron spectral range. Numerous absorption features characterized in the HITRAN compilations (e.g. Rothman et al., 2008) are encompassed in this mid-infrared region. Their analyses with either the SFIT-1 or SFIT-2 algorithm allow retrieving total columns of the target gases. Moreover, information on their distribution with altitude can generally be derived when using SFIT-2 which implements the Optimal Estimation Method of Rodgers (1990). Among the two dozen gases of atmospheric interest accessible to the ground-based FTIR technique, we have selected here a suite of long-lived halogenated species: HCl, ClONO2, CCl2F2, CCl3F, CHClF2, CCl4 and SF6. Time series available from the two sites will be presented, compared and critically discussed. In particular, changes in the abundances of theses gases since the peak in inorganic chlorine (Cly, which occurred in 1996-1997) and their intra-annual variability will be characterized with a statistical tool using bootstrap resampling (Gardiner et al., 2008). Trends and their associated uncertainties will be reported and put into perspective with the phase-out regulations of the production of ozone depleting substances adopted and implemented by the Montreal Protocol, its Amendments and Adjustments. For instance, the trends affecting the reservoir species HCl, ClONO2, and their summation which is a good proxy of the total inorganic chlorine, have been calculated using all available daily mean measurements from January 1996 onwards. The following values were obtained for Jungfraujoch, when using 1996 as the reference year: -0.90±0.10%/yr for HCl, -0.92±0.26 %/yr for ClONO2, and -0.96±0.14 %/yr for Cly; in all cases, the uncertainties define the 95% confidence interval around the trend values. For Kitt Peak, the corresponding trends are: -0.55±0.34 %/yr for HCl, -1.27±0.84 %/yr for ClONO2 and -0.61±0.51 %/yr for Cly, they are statistically consistent with the Jungfraujoch rates of decrease. Further trend data will be presented at the EGU General Assembly while supplementary information on Jungfraujoch results will be available from communications at the same meeting by Duchatelet et al. (2010), Lejeune et al (2010) and Rinsland et al (2010). Comparisons with model data are also foreseen. [less ▲]

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See detailModelling climate control on cropland and grassland development using phenologically tuned variables
Horion, Stéphanie; Tychon, Bernard ULg; Cornet, Yves ULg

in Geophysical Research Abstracts (2010), 12

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Using time series of remote sensing and climate data, Nemani et al ... [more ▼]

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Using time series of remote sensing and climate data, Nemani et al. (2003) analyzed trends in Net Primary Production in relation with changes in climate and showed that, between 1982 and 1999, primary productivity increased by 6% globally in response to climate change. This study also stressed the need to take into account the spatial variability of climatic constraints to plant growth when analyzing the climate change impact on vegetation. Others authors described different phenomenon linked with climate change such as increases of seasonal NDVI amplitude and growing season duration in the Northern high latitude or changes in circumpolar photosynthetic activities. Understanding the interactions between climate and vegetation is also a key issue in our PhD research. Our objective is to identify the meteorological factors which limit the development of croplands and grasslands in relation with their geographical localization. For that purpose, we acquired 10-daily time series of the Normalized Difference Vegetation Index, NDVI, derived from SPOT-VEGETATION and 7 meteorological parameters (Tmean, Tmin, Tmax, Rain, Rad, ETP, Rain-ETP) derived from ERA40 re-analyses and the operational ECMWF (European Centre for Medium-Range Weather Forecast) atmospheric model. Cross-correlations between NDVI and each one of the meteorological parameters were analysed for a set of 25 regions over Europe and Africa: 15 agricultural regions and 10 regions covered by grassland or savannas. Unlike others studies, we did not consider the vegetation globally but we focussed on two types of vegetation: croplands and grasslands. This is quite important considering the role of phenology on the vegetation cycle and its relation with climate. Moreover the analysis was not realised using yearly estimates but using 10-daily products. In order to avoid stationarity related issue, a specific methodology was developed taking into account the phenological cycle of the vegetation under consideration. Preliminary results showed that the relation between a meteorological limiting factor, e.g. precipitation, and NDVI can not be considered as linear during the year or even during the growing season. Interactions must to be studied at a smaller time scale than the growing season in order to identify properly the limiting factors to plant growth taking into account its phenology. Moreover the main limiting factors are variable from a region to another. In our analysis we also considered the possibility of a delayed response of the vegetation or a cumulated effect of meteorological events (up to 3 months). Our methodology will be presented during the conference and results will be discussed and illustrated by some test cases. [less ▲]

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See detailElectrical resistivity tomography and self-potential case studies for fractured aquifer characterization and monitoring
Robert, Tanguy ULg; Dassargues, Alain ULg; Nguyen, Frédéric ULg

in Geophysical Research Abstracts (2010), 12

Electrical resistivity tomography (ERT) and self-potential (SP) investigations have been conducted in complex carboniferous limestones aquifers in Belgium (synclinorium structures). The aims of this study ... [more ▼]

Electrical resistivity tomography (ERT) and self-potential (SP) investigations have been conducted in complex carboniferous limestones aquifers in Belgium (synclinorium structures). The aims of this study were (1) to detect and characterize fractured zones in hard rock aquifers, (2) to monitor groundwater flow/water content in these fractured or karstic areas and (3) to use geophysical data to support groundwater flow model set-up and calibration. The investigated areas lie in calcareous synclines. Electrical images allowed us to detect and characterize (in terms of direction, width and depth) several less resistive anomalies, which are interpreted in terms of fractured and/or karstic zones. To interpret the ERT images, data errors as well as image appraisal indicators (resolution matrix, sensitivity matrix and DOI index) were analysed and compared. This allowed us to determine the depth of investigation of ERT and to avoid the misinterpretation of the resulting images. Inversions based on focusing scheme are tested against smoothness-constraint inversion on these field data to provide more realistic images on the basis of prior geological knowledge. Self-potential measurements were performed along the electrical profiles and allowed us to find negative anomalies possibly related with groundwater preferential flow pathways. By taking the assumption that only the electrokinetic effect plays a role in the SP signals, we were able to estimate a first distribution of the water table along our profiles. The SP data showed that in this particular tectonic structure, two perpendicular hydraulic gradients are present. The first gradient is related with the main fold axis direction and is the major drainage system. The second hydraulic gradient is related with the flanks of the calcareous valley. Geophysical data concurrently with ‘ground truth’ geological and hydrogeological data allowed us to better understand the groundwater flow in these calcareous synclines and to verify the conceptual groundwater flow model. [less ▲]

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See detailTime series of 12CO and 13CO at northern mid-latitudes: Determination of Partial Column and δ13C seasonal and interannual variations
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Rinsland, C. P. et al

in Geophysical Research Abstracts (2009, April), 11(EGU2009-10017-1),

Carbon monoxide (CO) is an important reactive gas in the troposphere. It is emitted at the ground level by fossil fuel combustion and biomass burning. Biogenic sources and oceans as well as oxidation of ... [more ▼]

Carbon monoxide (CO) is an important reactive gas in the troposphere. It is emitted at the ground level by fossil fuel combustion and biomass burning. Biogenic sources and oceans as well as oxidation of methane and nonmethane hydrocarbons complete the emissions budget. Large uncertainties still affect the relative contributions of the identified anthropogenic and natural sources. Destruction by the hydroxyl radical (OH) is the main removal process for CO in both the troposphere and the stratosphere. The resulting average tropospheric lifetime of CO varies from several weeks to a few months. Two approaches have been developed and optimized to independently retrieve abundances of 12CO and 13CO from high-resolution ground-based infrared solar spectra, using sets of carefully selected lines and the SFIT-2 (v3.91) algorithm which implements the optimal estimation method. The corresponding products will be described and characterized in terms of error budget and information content. These strategies have allowed us to produce partial column time series of 12CO and 13CO, using spectra recorded on a regular basis at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580 m asl, Swiss Alps), a site of the Network for the Detection of Atmospheric Composition Change (NDACC). The seasonal and interannual changes observed in the 12CO,13CO and δ13C (13C/12C) data sets will be presented and discussed. Complementary zonal mean time series derived from occultation measurements collected by the ACE-FTS instrument onboard the Canadian SCISAT-1 platform since 2004 will also be included and analyzed, focusing on the upper troposphere-lower stratosphere region of the atmosphere. Finally, we will use GEOS-Chem 3-D chemistry transport model results to help in the interpretation of the short and long-term variations characterizing the ground-based and satellite data sets, focusing on the factors influencing the partitioning between the two CO isotopologues. [less ▲]

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See detailLocal electron density reconstruction from simultaneous ground-based GNSS and ionosonde measurements
Stankov, Stanimir; Warnant, René ULg; Stegen, Koen

in Geophysical Research Abstracts (2009, April), 11(Abs. No EGU2009-10956),

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See detailOn the TEC short-term forecast with corrections based on the average ionospheric response to background and storm-time geomagnetic conditions
Stankov, Stanimir; Warnant, René ULg; Kozarev, R.

in Geophysical Research Abstracts (2009, April), 11(Abs. No EGU2009-13283),

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See detailPaleolimnological and Sedimentological Traces of the 1943 (Ms=7.3) Earthquake in the sediments of Ladik Lake, Samsun/Turkey
Ulas, Avsar; Hubert, Aurelia ULg; Fagel, Nathalie ULg et al

in Geophysical Research Abstracts (2009, April), 11(EGU2009-12641-1),

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See detailThe Earthquake Sedimentary record of The Lake Hazar along the East Anatolian Fault in Turkey
Boes, Xavier; Hubert, Aurelia ULg; Garcia, David et al

in Geophysical Research Abstracts (2009, April), 11

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See detailPaleo-earthquake timing on the North Anatolian Fault: Where, when, and how sure are we?
Fraser, J; Vanneste, K.; Hubert, Aurelia ULg

in Geophysical Research Abstracts (2009, April), 11

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See detailLong Neogene kinematic history and late Quaternary order-of-magnitude acceleration of the south Tianshan foldbelt, Kuqa basin, China
Suppe, J; Wang, X; Hubert, Aurelia ULg

in Geophysical Research Abstracts (2009, April), 11

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See detailA relict sedimentary record of 7 earthquakes between 600AD and 2000BC on the central North Anatolian Fault at Elmacik, near Osmancik, Turkey
Fraser, J.G.; Vanneste, K.; Hubert, Aurelia ULg

in Geophysical Research Abstracts (2009, April)

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See detailNo earthquake with characteristic slip on the North Anatolian Fault, Turkey
Hubert, Aurelia ULg; Fraser, J.; Drab, L. et al

in Geophysical Research Abstracts (2009, April)

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See detailNew multi-station and multi-decadal trend data on precipitable water. Recipe to match FTIR retrievals from NDACC long-time records to radio sondes within 1mm accuracy/precision
Sussmann, Ralf; Borsdorf, Tobias; Rettinger, M. et al

in Geophysical Research Abstracts (2009), 11

We present an original optimum strategy for retrieval of precipitable water from routine ground-based midinfrared FTS measurements performed at a number globally distributed stations within the NDACC ... [more ▼]

We present an original optimum strategy for retrieval of precipitable water from routine ground-based midinfrared FTS measurements performed at a number globally distributed stations within the NDACC network. The strategy utilizes FTIR retrievals which are set in a way to match standard radio sonde operations. Thereby, an unprecedented accuracy and precision for measurements of precipitable water can be demonstrated: the correlation between Zugspitze FTIR water vapor columns from a 3 months measurement campaign with total columns derived from coincident radio sondes shows a regression coefficient of R = 0.988, a bias of 0.05 mm, a standard deviation of 0.28 mm, an intercept of 0.01 mm, and a slope of 1.01. This appears to be even better than what can be achieved with state-of-the-art micro wave techniques, see e.g., Morland et al. (2006, Fig. 9 therein). Our approach is based upon a careful selection of spectral micro windows, comprising a set of both weak and strong water vapor absorption lines between 839.4 – 840.6 cm-1, 849.0 – 850.2 cm-1, and 852.0 – 853.1 cm-1, which is not contaminated by interfering absorptions of any other trace gases. From existing spectroscopic line lists, a careful selection of the best available parameter set was performed, leading to nearly perfect spectral fits without significant forward model parameter errors. To set up the FTIR water vapor profile inversion, a set of FTIR measurements and coincident radio sondes has been utilized. To eliminate/minimize mismatch in time and space, the Tobin best estimate of the state of the atmosphere principle has been applied to the radio sondes. This concept uses pairs of radio sondes launched with a 1-hour separation, and derives the gradient from the two radio sonde measurements, in order to construct a virtual PTU profile for a certain time and location. Coincident FTIR measurements of water vapor columns (two hour mean values) have then been matched to the water columns obtained by integrating the best-estimate radio sonde profiles. This match was achieved via investigating the quality of the correlation plots between the columns derived from the radio sondes and the FTIR retrievals, and iteratively tuning the regularization strength of the FTIR retrieval. The FTIR regularization matrix is based on a Tikhonov operator which allows for empirical tuning of the regularization strength via one parameter. The figures of merit for the iterative tuning have been the slope, the intercept, and the regression coefficient of the correlation. By this way an optimum retrieval setting could be found, guaranteeing a response of the FTIR retrievals to true water vapor changes, which is matched to the radio sonde operation. As first examples for utilizing this approach to derive long-term trends of precipitable water from NDACC type long-term FTIR measurements, we present trends from two time series. I.e., one retrieved from continuous FTIR measurements at the NDACC Primary Station Zugspitze, Germany (47.42 °N, 10.98 °E, 2964 m a.s.l.), which covers the time span 1995-2009, and one from the International Scientific Station of the Jungfraujoch (ISSJ, 46.5°N, 8.0°E, 3580m a.s.l., Swiss Alps), covering the time span 1984 – 2009. A detailed trend analysis of both series via the bootstrap method will be presented. In ongoing work we apply this optimum retrieval approach to historical long-time measurement series of further selected FTIR stations of the NDACC network. Thereby we will obtain unprecedented new climate data via long term trends of precipitable water at a set of globally distributed locations. [less ▲]

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See detailA 3000 year chronology of North Anatolian Fault ruptures, utilizing magnetic susceptibility trench logging, near Lake Ladik, Turkey
Fraser, J; Pigati, J; Hubert, Aurelia ULg et al

in Geophysical Research Abstracts (2008, April), 10

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See detailTraces of the last earthquake sequence (1939-1944) along NAF from lacustrine sediments
Avsar, Ulas; Boes, X; Hubert, Aurelia ULg et al

in Geophysical Research Abstracts (2008, April), 10

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See detailRadionuclide profiles and recent earthquakes history of Lake Hazar Pull-apart basin (East Anatolian Fault, Turkey)
Boes, Xavier; Moran, B.; Kelly, R. et al

in Geophysical Research Abstracts (2008, April), 10

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See detailThe Hazar pull-apart along the East Anatolian Fault: Structure and active deformation
Garcia Moreno, David; Hubert, Aurelia ULg; Moernaut, J et al

in Geophysical Research Abstracts (2008, April), 10

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See detailOn-the-go georeferenced measurements of soil mechanical strength and differenciation of soil structure.
Destain, Marie-France ULg; Sirjacobs, Damien ULg; Hanquet, Bernard et al

in Geophysical Research Abstracts (2008)

Soil strength is defined as the resistance which as to be overcome to obtain a given soil deformation. Amongst the numerous methods developed to measure soil strength, two are classically used. On one ... [more ▼]

Soil strength is defined as the resistance which as to be overcome to obtain a given soil deformation. Amongst the numerous methods developed to measure soil strength, two are classically used. On one hand, a laboratory method based on triaxial tests of undisturbed soil samples allows the estimation of cohesion and internal friction angle by the Mohr-Coulomb equation. On the other hand, measuring soil penetration resistance by pushing a cone into a soil is a widely used technique. Both techniques deliver discontinuous field information and are not suited to produce digital soil mapping. The objectives of this paper are to present a sensor able to continuously measure soil strength variations. The sensor was constituted of a thin blade pulled in the soil at a constant depth and speed and a beam which transferred the soil-blade forces to a transducer fixed on a vehicle. The transducer measures the draft force Fx, the vertical force Fz and the moment My thanks to an octagonal ring dynamometer. A measurement chain was developed to acquire simultaneously the signals provides by the soil strength sensor and those of a DGPS. Signal processing was notably based on geostatistics and allows soil mapping [1]. Four fields representative of the soils used in silty areas for arable production in Belgium were selected. The measurements were repeated several times during 1999-2003. Targeted test plots were chosen in each field to perform reference measurements, namely granulometry, cohesion, friction angle, pF, water content, dry bulk density, and cone index. The within-field studies revealed high variability caused by texture, history, traffic, etc., and showed a correlation between the sensor signals and physical parameters, such as cone index and soil moisture, as long as no over-consolidation of the soil occurred [2]. To assess the similarity of soil strength between the fields, the data Fx, Fz and My were classified by using canonical variates (CV). The two first CV represented 95.9 % of the variability, which means that two main variables contain the essential part of the information. In a plane (Fz, Fx), three clusters could be distinguished. The first one (trials 1 and 5), characterized by a low draft and a high Fz, corresponded to trials performed in March on soils ploughed during the winter, naked or covered with small vegetation, and characterized by small values of cone index. The second one (trials 2, 3, 4, 7) with high values of Fx and Fz grouped measurements done just after wheat harvest in August. The third cluster (trials 6) corresponded to measurements performed during wheat growth. It may be concluded that the signals from the sensor treated by suited statistical analysis have the potential to differentiate soil structures at a field scale. REFERENCES [1] Sirjacobs D., Hanquet B., Lebeau F., Destain M.-F. (2002). On-line mechanical resistance mapping and correlation with soil physical properties for precision agriculture. Soil and Tillage Research 64, 231-242. [2] Hanquet B., Sirjacobs D., Destain M.-F., Frankinet M., Verbrugge J.-C. (2004). Analysis of soil variability measured with a soil strength sensor. Precision Agriculture, 5, 227-246. [less ▲]

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