Showing papers in "The EGU General Assembly in 2009"

The Upper Danube soil moisture validation site: measurements and activities

Abstract: The validation of soil moisture products from ESA’s Soil Moisture and Ocean Salinity (SMOS) mission requires the maintenance of long term soil moisture monitoring sites. The Upper Danube catchment, situated mostly in Southern Germany, was chosen as one of two main test sites in Europe for the SMOS cal/val activities. Its main part is situated in the alpine foreland with heterogenous land cover and large natural gradients from the Alps northwards. Best soil moisture retrieval performance is expected in the smaller catchment of the river Vils, because there are neither open water bodies nor large urban areas and terrain as well as soil texture are fairly homogeneous. The Vils reference site is equipped with a more dense network of currently 5 soil moisture measuring stations as it is the focus of flight campaigns and studies of scaling issues. THE UPPER DANUBE SOIL MOISTURE VALIDATION SITE: MEASUREMENTS AND ACTIVITIES

Synoptic typing and its application to the investigation of weather - air pollution relationships in Kuwait

Abstract: Principal components analysis and cluster analysis of surface meteorological data were used to derive the different air mass types for Kuwait. The air mass types were analysed in terms of their mean meteorological and associated weather chart characteristics in order to relate them to their different synoptic situations. The air mass types were subsequently analysed with air pollutant concentration data. Here we report on the identified air mass types, their seasonal dependence and their pollution characteristics. Analysis of the air mass types according to pollutant mean and extreme values helps to identify the different meteorological and transport conditions influencing pollution in this region.

The European heat wave 2003: early indicators from multisensoral microwave remote sensing?

Abstract: An extreme heat wave affected large parts of Europe in 2003 with severe socioeconomic impacts. The extreme warm weather conditions lasted over a couple of months with positive temperature anomalies of 5°C for large parts of Europe. Simulations of the event using regional climate models revealed that a pronounced precipitation deficit in the beginning of the year, together with an early onset of the vegetation, resulted in a severe deficit of the soil water content. This amplified the course of the heat wave due to an increasing sensible heat flux from the land surface.

Microseismic activity analysis for the study of the rupture mechanisms in unstable rock masses (Matterhorn, North-western Alps)

Abstract: Abstract. Rockfalls are common instabilities in alpine areas and can cause significant damage. Since high mountains have been affected by an increasing number of these phenomena in the last years, a possible correlation with permafrost degradation induced by climate change has been hypothesized. To investigate this topic, a monitoring system, made of 5 triaxial geophones and 1 thermometer, was installed in 2007 at the Carrel hut (3829 m a.s.l., Matterhorn, North-western Alps), in the frame of the Interreg IIIA Alcotra project n. 196 \"Permadataroc\". The preliminary data processing relates to the classification of recorded signals, the identification of the significant microseismic events and the analysis of their distribution in time and space. The first results indicated a possible correlation between clusters of events and temperature trend, and a concentration of events in specific sectors of the rock mass. Research is still in progress. The recording of data for a longer period is planned to fully understand seasonal trends and spatial distribution of microseismic activity, and possible relations with permafrost degradation. Nevertheless, the preliminary observations prove that the monitoring system can detect noises generated by rock slope deformation. Once fully developed, this technique could become a helpful tool for early warning and preliminary stability assessments.

First Results from the International Urban Energy Balance Model Comparison: Model Complexity

Abstract: A great variety of urban energy balance models has been developed. These vary in complexity from simple schemes that represent the city as a slab, through those which model various facets (i.e. road, walls and roof) to more complex urban forms (including street canyons with intersections) and features (such as vegetation cover and anthropogenic heat fluxes). Some schemes also incorporate detailed representations of momentum and energy fluxes distributed throughout various layers of the urban canopy layer. The models each differ in the parameters they require to describe the site and the in demands they make on computational processing power. Many of these models have been evaluated using observational datasets but to date, no controlled comparisons have been conducted.

Soil moisture retrieval from passive microwave data: A sensitivity study using a coupled SVAT-radiative transfer model at the Upper Danube anchor site.

Abstract: As passive microwave remote sensing data is sensitive to the surface soil moisture, recent satellite mission concepts, like the Soil Moisture and Ocean Salinity (SMOS) mission, to measure the surface soil moisture content with L-band passive microwave sensors will provide global soil moisture information with a high temporal resolution of about 1-3 days. In contrast, the spatial resolution used for the retrieval of the soil moisture from SMOS images will be rather coarse, in the order of tens of kilometres. The provided soil moisture information is therefore integrated over a large area that may be composed of different land covers and soils. Uncertainties of the soil moisture retrieval depend on the accuracy and spatial resolution of ancillary data, like land use information data, which is necessary for the retrieval. The sensitivity of the retrieval to different land cover information datasets is investigated, using a coupled SVAT-radiative transfer-model comparing the standard land use map used within the SMOS Level 2 soil moisture processor with a well established map for the study area. The used approach shows big differences of the retrieval in some parts of the study area while in others the retrieved soil moisture is nearly the same with both land cover maps used.

Surface ocean iron fertilization: the role of airborne volcanic ash and iron-flux into the Pacific Ocean

Abstract: Iron is a limiting micro-nutrient for marine primary production (MPP) in vast areas in the surface ocean. Hence, atmospheric supply of iron to the surface ocean can affect marine biogeochemical cycles, associated oceanatmosphere exchange of CO2 and eventually climate development. Airborne volcanic ash from volcanic eruptions can be an important atmospheric iron-source in the surface ocean by releasing bio-available iron while settling through in the surface ocean. Here we present new data from time-dependent geochemical experiments with pristine (unhydrated) volcanic ash samples and natural seawater by means of Cathodic Stripping Voltammetry. Our results demonstrate that volcanic ash mobilizes significant amounts of soluble Fe within 60 minutes of contact with natural seawater. Depending on the amount of volcanic ash deposited offshore during major volcanic eruptions and the amount of iron that ash can release on contact with seawater, the calculated increase in the surface ocean Fe levels range from several nanomolar up to several hundred nanomolar (nM). Only 2 nM increase in iron concentrations can stimulate massive diatom blooms in the oceanic regions in which MPP is limited by the availability of iron (the iron-limited oceanic areas) (Wells, 2003). Therefore volcanic ash should be able to significantly affect marine phytoplankton growth in an ash fall area, acting as an iron fertilizer. Based on our new iron-release data and marine sediment core data we provide the first estimate of the flux of Fe from volcanic ash into the Pacific Ocean that covers more than 60 percent of the iron-limited oceanic regions. Our calculations show that the flux of Fe from volcanic ash is comparable to the order of magnitude of the flux of Fe from aeolian dust. Our study shows that volcanic ash is a major and so far underestimated atmospheric iron-source for the oceans and therefore an important component in marine biogeochemical iron cycles.

GPR application to historical buildings structural control

Abstract: Preservation of historical buildings requires particular care, as any intervention must conducted in a way which does not alter or damage the style, structure or contents of the edifice. In order to properly plan the restoration of a building, non-destructive techniques can be extensively used to detect structural elements and weaknesses. Ground Penetrating Radar is particularly well adapted to this type of work, as the method is non-invasive, rapid, and provides high resolution images of contrasting subsurface materials. In the present work we show three case-histories on three historical buildings – different in age, structure and geometry – in which GPR technique has been successfully used. To obtain 2D time slices of the investigated area, high frequency bistatic GPR (900 MHz and 1GHz antennas) was applied in each site, acquiring data along several parallel profiles. The first case presented here, is the GPR detection of the fractures and the internal lesions in the architrave of the Porticus Octaviae, a Roman building partially restored, located downtown Rome. The second case shows the application of the GPR to detect the internal structure of the floors above the vaulted ceilings that houses a series of 16th century frescos in the important Zuccari Palace, also located in Rome. Finally, the third case illustrates the application of GPR to reconstruct the geometry and the reinforcement structures of the floors and the inside walls of the Provincial Palace of Pescara, dated back to the Fascist age. These three examples show that GPR technique is a valid support which, in exhaustive way, can highlight the state of conservation of historical buildings. In particular, this technique can produce fundamental information for the restorers, in terms of location, dimension, and geometry of the internal lesions in the structure, helping them in developing the best possible protection plan for an historical building.

Adaptation of the HBV model for the study of drought propagation in European catchments

Abstract: Drought propagation is the conversion of a meteorological drought signal into a hydrological drought (e.g. groundwater and streamflow) as it moves through the subsurface part of the hydrological cycle. The lag, attenuation and possibly pooling of parts of the signal are dependent on climate and catchment characteristics. The understanding of processes underlying drought propagation is still very limited. Our aim is to study these processes in small catchments across Europe with different climate conditions and physical structures (e.g. hard rock, porous rock, flat areas, steep slopes, snow, lakes). As measurements of soil moisture and groundwater storage are normally scarce, simulation of these variables using a lumped hydrological model is needed. However, although a simple model is preferable, many conceptual rainfall-runoff models are not suitable for this purpose because of their focus on fast reactions and therefore unrealistic black box approach of the soil moisture and groundwater system. We studied the applicability of the well-known semi-distributed rainfall-runoff model HBV for drought propagation research. The results show that HBV reproduces observed discharges fairly well. However, in simulating groundwater storage in dry periods, HBV has some conceptual weaknesses: 1) surface runoff is approximated by a quick flow component through the upper groundwater box; 2) the storage in the upper groundwater box has no upper limit; 3) lakes are simulated as part of the lower groundwater box; 4) the percolation from the upper to the lower groundwater box is not continuous, but either zero or constant. So, adaptation of the HBV model structure was needed to be able to simulate realistic groundwater storage in dry periods. The HBV Light model (Seibert et al., 2000) was used as basis for this work. As the snow and soil routines of this model have proven their value in previous (drought) studies, these routines are left unchanged. The lower part of HBV Light, the "response function" that transforms groundwater recharge into discharge, is replaced by a for this study adapted conceptual research model programmed in R. The structure of this conceptual research model is based on a number of coupled reservoirs representing storage in shallow and deep groundwater, and lakes. The recession characteristics of the catchment determine the model elements: i.e. number of reservoirs, linear vs. non-linear reservoirs, in series vs. parallel connections. We used data from Narsjo (Norway), Metuje and Sazava (Czech Republic) to select the proper configuration for the conceptual research model and to test the combined HBV Light-conceptual research model approach. The influence of different model configurations on drought characteristics is presented. Subsequently, the new approach was applied to 4-5 other European catchments with contrasting climate conditions and physical structures (including Nedožery (Slovakia), and Upper-Guadiana (Spain)). Our adapted model approach finally gives a better representation of groundwater storage during drought periods than the original HBV model, which makes it a useful tool for the study of processes underlying drought propagation. Simulated drought characteristics are shown to illustrate drought propagation for the different catchment conditions.

Broom fibre PRB for heavy metals groundwater remediation

Abstract: Soil contamination by heavy metal and, though it, of groundwater represent a serious alteration of original geochemical levels owing to various human activities as: particular industrial processes and their non-correct treatment emission, urban traffic, use of phytosanitary product and mineral fertilizer. Heavy metals are genotoxic contaminants who can be found by environmental matrix analysis or by examination of the genetic damage inducted, after exposition, to sentry organism. In this last case we use a relative quantitation of the gene expression monitoring the mitochondrial oxidative metabolism hepatopancreas’s gene of the organism used by bioindicator. This test is based on consideration that the hepatopancreas is the first internal organ affected by heavy metals or any other pollutant that the organism is exposed. In this work, the organism used by bioindicator to evalutate the pollutant contamination of waste water is Danio rerio (Zebrafish) that is a little tropical fish of 2-3 cm, native on asiatic south-east rivers. This organism has a large use in scientific field because its genoma is almost completely mapped and, above all, because the congenital gene cause in human, if it was mutated in zebrafish, similar damage or almost similar mutation that happens in human being so you can develop a dose – response curve. To do this, after prepared a cadmium solution with a concentration 10 times the Italian normative limit, the organisms have been put in the aquarium to recreate the optimal condition to survival of zebrafish observed by continuous monitoring by web-cam. After one month exposition, that we took little by little sample fish to analyzing, for different exposition time, the hepatopancreas’s fish. First results shows considerable variation of the gene expression by interested gene in mitochondrial oxidative metabolism compared to control, highlighting the mutagenity caused by heavy metals on Danio rerio’s hepatopancreas and, mutatis mutandis, also in human being. One of the most interesting techniques applied in contaminated aquifer by heavy metals is the PRBs (Troisi et al., 2002; Calvin et al., 2006), in particular broom fibers PRB (Troisi et al., 2008). The first results highlight an optimum removal capacity for contaminants underlined from following removal percentage: 98.01% (Cd), 99.95% (Cu), 97.35% (Pb) and 99.53% (Zn). A fundamental parameter for PRB design is the decay coefficient who indicates the removal capacity (degradation, transformation, adsorption/absorption, mass transport, etc.). This parameter has been determined for four heavy metals: Cadmium (Cd), Copper (Cu), Lead (Pb) and Zinc (Zn) carrying out column tests. Besides, for real use of broom fibers PRB same tests have been performed, using flow cells, to estimate a relation between hydraulic conductivity of fiber and its density.

Cosmogenic exposure ages of glacial boulders from the Tibetan Plateau - Age distributions support boulder exhumation/erosion and indicate old glacial deposits.

Abstract: Terrestrial cosmogenic nuclide (TCN) exposure dating has become the most dominant technique for constraining glacial chronologies. This is particularly true for the Tibetan Plateau because of its l ...

Multisource geophysical investigation of the Acıgöl caldera structure (central Turkey): preliminary results

Abstract: Neogene and Quaternary volcanic activity formed the large volume ignimbritic units (about 10 different units, namely Cappadocian ignimbritic field) around Nevsehir, Derinkuyu and Acigol districts. These large volume ignimbrites are mostly caldera-related products but the calderas are partially or totally buried by later pyroclastic and sedimentary cover. Source estimations for the caldera-related pyroclastics in Nevsehir plateau indicate that the calderas concentrate around Derinkuyu and Acigol plains. Geophysical methods (resistivity imaging, self-potential, TDEM and magnetic surveys) were applied around Acigol plain and Mt. Erdas to reveal out the near-surface structural elements related to the Acigol caldera system. Additionally, remote sensing coupled with morphology was used. Preliminary results show that the Acigol caldera complex may have an elongated shape. Possible structural models for the caldera system/complex are explained. Future geophysical studies and a detailed study of the geological relationship between the caldera-related products are necessary to better understand the Acigol caldera system. (Less)

Changes in the North Atlantic Oscillation influence CO2 uptake in the North Atlantic over the past 2 decades

Abstract: Observational studies report a rapid decline of ocean CO2 uptake in the temperate North Atlantic during the last decade. We analyze these findings using ocean physical‐biological numerical simulations forced with interannually varying atmospheric conditions for the period 1979–2004. In the simulations, surface ocean water mass properties and CO2 system variables exhibit substantial multiannual variability on sub‐basin scales in response to wind‐driven reorganization in ocean circulation and surface warming/cooling. The simulated temporal evolution of the ocean CO2 system is broadly consistent with reported observational trends and is influenced substantially by the phase of the North Atlantic Oscillation (NAO). Many of the observational estimates cover a period after 1995 of mostly negative or weakly positive NAO conditions, which are characterized in the simulations by reduced North Atlantic Current transport of subtropical waters into the eastern basin and by a decline in CO2 uptake. We suggest therefore that air‐sea CO2 uptake may rebound in the eastern temperate North Atlantic during future periods of more positive NAO, similar to the patterns found in our model for the sustained positive NAO period in the early 1990s. Thus, our analysis indicates that the recent rapid shifts in CO2 flux reflect decadal perturbations superimposed on more gradual secular trends. The simulations highlight the need for long‐term ocean carbon observations and modeling to fully resolve multiannual variability, which can obscure detection of the long‐term changes associated with anthropogenic CO2 uptake and climate change.

Carbon Cycling in the Arctic Archipelago: The Export of Pacific Carbon to the North Atlantic

Abstract: . The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and is thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as intermediate salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO 2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.

Towards better predictions of snow melt runoffs : measuring snow depth and density using ground penetrating radar

Abstract: Snow melt runoff predictions by hydrological models are essential for efficient hydropower production in the Scandinavian countries, similar to many areas with a substantial amount of snow precipitation. Operational models in Sweden are currently based on precipitation and temperature as the main input variables and calibrated with runoff data, but there is an interest to make better use of new measurement systems for distributed snow data, especially the total amount of snow in the catchment area of interest. The main objective of our project is to investigate the potential improvements in runoff predictions in relation to the choice of model structure and measurement systems, as well as measurement accuracy. This involves comparing different methods for estimating the total amount of snow in a catchment area as well as improving their accuracy. Here we present the result of such comparison based on data from case studies conducted in Sweden. Our approach involves automated single point measurements over a long period in combination with high resolution distributed measurements over a large area during critical periods. Stationary measurements are performed at a snow measurement station, with snow density and wetness estimated with a low-frequency impedance sensor band, snow depth measured using an ultrasonic depth gauge, and temperature measured at several (fixed) snow depths and at the snow surface. The station, located at Lake Korsvattnet in Swedish mountains, operates continuously during the whole winter season. Measurements of snow depth and density over large lateral distances are performed using multi-offset ground penetrating radar (GPR) operated from a snow mobile. These measurements are conducted once a year, in late winter, when the amount of snow is expected to reach its maximum before snow melt begins. Since 2007 and during the duration of the project, yearly measurements have been and will be taken in two Swedish mountain basins important for hydropower, Lake Korsvattnet and Lake Kultsjon. The radar system used is a multi-channel RAMAC/GPR system with shielded 800 and 1600 MHz antennas. The antennas are attached to a snow mobile sledge forming an array, which allows us to use the common midpoint method to calculate both radar propagation velocity and two-way travel time of radar pulses. For dry snow this gives snow density and depth via an empirical formula establishing the relationship between electrical permittivity (i.e. propagation velocity) and snow density. Note that for wet snow additional information about liquid water content in snow is required, which can be estimated, for example, from radar wave attenuation. However, for the purpose of this presentation we assume that the snow is dry. The results of GPR measurements taken from a snow mobile are compared with results obtained by two other methods. The first comparison is with manual measurements taken with traditional snow tubes along a 1000 m measurement profile at the area of Lake Korsvattnet. In this case a log-linear relationship between snow depth and density is used to interpret GPR data (note that this relationship is obtained from analysis of radar data itself). The other comparison is with GPR measurements taken from a helicopter along a 12 km transect in the area of Lake Kultsjon.

Assessment of dam impacts on sediment dynamics and channel geometry in complex anthropogenic systems : feedbacks from comparative study of the Sacramento and the Ain Rivers

Abstract: Numerous studies have demonstrated the complexity of river adjustments downstream dams (Williams and Wolman, 1984; Brandt, 2000; Petts and Gurnell, 2005), depending on many parameters such catchment geology context (Grant et al., 2003), land use, pre-dam sediment supply and transport regime, degree of hydrologic alteration (Church, 1995; Schmidt and Wilcock, 2008), and dam characteristics and operation (Brewer and Lewin, 1998). Dam impact is particularly difficult to evaluate in river systems where human pressures are old and manifold, and where dam-induced impacts can be compounded by other human influences, such as in-channel aggregate mining (Kondolf 1997). In such cases, it may be challenging to sort out the causal links between dam-induced disruptions and resulting channel adjustment. To illustrate these problems, we introduce two complex case studies, the Ain (France) and Sacramento (California) Rivers, both freely meandering rivers regulated since mid-20th century, whose sedimentary and morphologic dynamic have been modified in different ways since the end of the 19th century. Dam impacts can be distinguished from the effects of other factors such as floodplain disconnection by flood-control infrastructure, land-use changes, and artificial meander-bend cutoff. The Ain River evinces a significant sediment deficit, which results in bed degradation, decrease in area of gravel bars , and reduced lateral channel migration. As a result, sediment supply is reduced not only from trapping by upstream reservoirs but also by reduced bank erosion. In the case of the Sacramento, the impact of the dam is not as clear as on the Ain due to major effects of prior pressures on the channel. Using aerial imagery and field measurements (grain-size measurements…), we led a spatiotemporal study of several morphologic parameters (active channel narrowing, gravel bar areas …) to underline the relative contribution of dams to the contemporary channel evolution. These analyses are now used as fundamental basis to define sediment management plans pertinent and adapted to each context. Moreover, in such complex river systems, by underlining dam effects among several potential causes and adjustments, these studies provide strong arguments to involve dam and river managers into river dynamic restoration plans.