Top PDF Influence of proxy data uncertainty on data assimilation for the past climate

Influence of proxy data uncertainty on data assimilation for the past climate

Influence of proxy data uncertainty on data assimilation for the past climate

Abstract. Data assimilation (DA) is an emerging topic in palaeoclimatology and one of the key challenges in this field. Assimilating proxy-based continental mean temperature re- constructions into the MPI-ESM model showed a lack of information propagation to small spatial scales (Matsikaris et al., 2016). Here, we investigate whether this lack of re- gional skill is due to the methodology or to errors in the assimilated reconstructions. Error separation is fundamental, as it can lead to improvements in DA methods. We address the question by performing a new set of simulations, using two different sets of target data; the proxy-based PAGES 2K reconstructions (DA-P scheme), and the HadCRUT3v in- strumental observations (DA-I scheme). Again, we employ ensemble-member selection DA using the MPI-ESM model, and assimilate Northern Hemisphere (NH) continental mean temperatures; the simulated period is 1850–1949 AD. Both DA schemes follow the large-scale target and observed cli- mate variations well, but the assimilation of instrumental data improves the performance. This improvement cannot be seen for Asia, where the limited instrumental coverage leads to er- rors in the target data and low skill for the DA-I scheme. No skill on small spatial scales is found for either of the two DA schemes, demonstrating that errors in the assimilated data are not the main reason for the unrealistic representation of the regional temperature variability in Europe and the NH. It can thus be concluded that assimilating continental mean temper- atures is not ideal for providing skill on small spatial scales.
Mostrar mais

9 Ler mais

The influence of climate change on flood risks in France – first estimates and uncertainty analysis

The influence of climate change on flood risks in France – first estimates and uncertainty analysis

To assess our economic valuation methodology, the ex- pected flood losses per year (from Eq. 11) are summed over the whole territory and over the sub-catchments with sta- tions, in the five loss-ratio cases (Tab. 4). The area over which changes are computed corresponds to 70 % of total damages. This expected cost over France can be compared with the es- timation done by the insurance sector in FFSA (2009), which is around 0.865 billion Euro per year. This figure is quite sim- ilar with the expected costs evaluated in our study, although methodologies are completely different. It is difficult to pro- pose a real validation, since the floods over the last 30-yr – the period during which economic data on flood losses ex- ist – cannot be considered as representative of flood risks in France; for instance, no major flood of the Seine, the Loire or the Garonne occurred during this period.
Mostrar mais

13 Ler mais

Changes in atmospheric variability in a glacial climate and the impacts on proxy data: a model intercomparison

Changes in atmospheric variability in a glacial climate and the impacts on proxy data: a model intercomparison

There are a number of ways in which changes in the exter- nal forcing can affect atmospheric variability.We focus our discussion on ice sheets and greenhouse gases as these ex- hibit larger LGM-PI differences than insolation (see Fig. 1 in Otto-Bliesner et al., 2006). The large Laurentide ice sheet covering North America creates an upstream-blocking sit- uation that may be related to a stronger, but less variable, Atlantic jet at the LGM relative to the PI climate (Li and Battisti, 2008; Donohoe and Battisti, 2009). The reduced variance associated with the leading mode of SLP variability (Fig. 4) is broadly consistent with this change in upper-level jet variability; it could also be linked to the lower greenhouse gas concentrations at the LGM, much as the recent increase in NAO variance is thought be linked to external factors such as increases in greenhouse gas concentrations and/or changes in surface properties (Feldstein, 2002). Our results suggest that surface properties (SST and sea ice), are not important for determining the leading mode of SLP variability, but have some influence on the magnitude and pattern of interannual SLP variability. These findings are qualitatively consistent with the study of Kushnir et al. (2002), in which it is demon- strated that atmospheric variability is more affected by in- ternal atmospheric processes than by the extratropical ocean. Other studies suggest that sea ice anomalies can affect atmo- spheric variability, particularly the phase and amplitude of the NAO (Deser et al., 2000; Seierstad and Bader, 2008).
Mostrar mais

14 Ler mais

Investigating the usefulness of satellite derived fluorescence data in inferring gross primary productivity within the carbon cycle data assimilation system

Investigating the usefulness of satellite derived fluorescence data in inferring gross primary productivity within the carbon cycle data assimilation system

lated from the optimized parameter vector obtained from the calibration step. CCDAS has been widely applied to investigate terrestrial carbon cycling (e.g., Rayner et al., 2005; Scholze et al., 2007) and in particular more recently to (i) estimate the GPP at global scale (Koffi et al., 2012) and (ii) to quantify the uncertainty in the parameters of BETHY by using both CO 2 concentration and flux observational networks (Kaminski

43 Ler mais

Aerosol effective density measurement using scanning mobility particle sizer  and quartz crystal microbalance with the estimation of involved  uncertainty

Aerosol effective density measurement using scanning mobility particle sizer and quartz crystal microbalance with the estimation of involved uncertainty

The above discussions suggest that particle density depends more on particle chemical composition (which changes rapidly while particle growth occurs during the mid- day period) and morphology than on particle size. To further check this hypothesis with the results in this study, we com- pared ambient gaseous composition with observed densities. Figure 5 displays the mean particle effective density ver- sus count mean diameter over the size range 10–478 nm ob- served in mid-day during the sampling days. In each box, the line within the box shows the median effective density value which corresponds to a CMD value, the top and bottom lines of the box show the upper and lower quartiles (the 75th and 25th percentiles) and the top and bottom of the whiskers are set to 90 and 10 percentile. Considering more than 100 scans each day collectively, it was less often evident that the effective density increased with the particle mobility diame- ter, with a mean of 1.12 ± 0.3 g cm −3 at 82.84 ± 6.51 nm and
Mostrar mais

17 Ler mais

Effect of Annealing Time for Quenching CuAl7Fe5Ni5W2Si2 Bronze on the Microstructure and Mechanical Properties

Effect of Annealing Time for Quenching CuAl7Fe5Ni5W2Si2 Bronze on the Microstructure and Mechanical Properties

At this scale of temperature and time (Fig. 9) it is difficult to identify the characteristic changes of the sample temperature, respectively, during the annealing (stage T2 - isothermal annealing), hyperquenching and quenching bronze (stage T3 - cooling in ambient air and T4 stage - cooling in 10% NaCl solution in water). Figure 10 shows representative characteristics of temperature changes during the isothermal annealing bronze sample at a constant temperature of t=1000 °C for 3600 s. There was a decrease of the temperature characteristic bronze samples during the annealing process in the studied range of isothermal annealing time (30, 60 and 120 min.). The presented characteristics t=f(τ) for a sample of bronze in the furnace that, after heating the furnace and the sample to a temperature of 1000 °C, there was a gradual decrease in temperature of the sample to about 996°C. Decrease of the temperature of the sample is associated with absorption of heat by the phase existing in bronze at 1000 °C, necessary for the occurrence of the following diffusion processes:
Mostrar mais

18 Ler mais

An operational approach to high resolution agro-ecological zoning in West-Africa

An operational approach to high resolution agro-ecological zoning in West-Africa

This study demonstrates how a simple approach can generate relevant information on climate vulnerability and how it can be operationally used in rural extension services. In spite of cur- rent opportunities and international commitments in LDCs, governance difficulties, com- pounded by lack of knowledge, information, and sustainable financing still prevent true transformative processes towards integrated and spatially explicit agricultural development. The work performed and the results obtained highlight the opportunity and need of develop- ing tailored software that can quickly, easily, and inexpensively grant access to the full body of agro-ecological knowledge and data to assist food production and environmental sustainabil- ity. This study is the first application of this new AEZ approach and should be complemented by additional research and developments to improve its performance and support potential.
Mostrar mais

16 Ler mais

SOFT PATH WATER MANAGEMENT IN DRY AND ARID REGIONS OF THE ARABIAN PENINSULA BY RAINWATER HARVESTING

SOFT PATH WATER MANAGEMENT IN DRY AND ARID REGIONS OF THE ARABIAN PENINSULA BY RAINWATER HARVESTING

Water management in Saudi Arabia is facing major challenges due to the limited water resources and increasing uncertainties caused by climate change. To investigate the existence of any signs of climatic changes in Saudi Arabia, the rainfall records of the thirty-one years of period (1980-2010) were analyzed for thirteen cities the rainfall trend in the whole Kingdom covering the wide areas of the country. The magnitudes of the rainfall trend were derived from the slope values of the regression lines and were supported by the Durbon- Watson statistic. An increased annual total rainfall trend was observed in six cities while an increasing trend in annual maximum daily rainfall in thirteen cities was observed. These rainfall trends highlight the higher rainfall intensities or rainfall with longer duration in addition to the variability of climate pattern in different cities of the same district and in different months of the years. The resulting floods of short-duration due to increased rain intensities have caused more damage in well-developed cities and urban centers in recent years.
Mostrar mais

8 Ler mais

The application of optical measurements for the determination of accuracy of gear wheels casts manufactured in the RT/RP process

The application of optical measurements for the determination of accuracy of gear wheels casts manufactured in the RT/RP process

Rapid prototyping (RP) and rapid tooling (RT) systems are increasingly used in the production of casting components. RP systems can be used directly for manufacturing casting moulds [1- 9]. The spectrum of rapid prototyping uses can be expanded by the application of the rapid tooling methods. One of the RT techniques is the direct manufacture of casting moulds using the ZCast technology. The accuracy of gear wheels casts made in printed moulds depends on a variety of technological factors [10- 13]. The accuracy of the cast fabrication quality can be assessed with the use of the coordinate optical measuring technique [14- 16]. Literature describes the methods for manufacturing moulds in
Mostrar mais

4 Ler mais

Nitrogen assimilation in Citrus based on CitEST data mining

Nitrogen assimilation in Citrus based on CitEST data mining

Biochemical studies with Pisum sativum showed that AspAT (E.C.2.6.1.1) can exist as distinct isoenzymes. In citrus, this was the only enzyme found in the four analyzed tissues, leaf, fruit, bark and root, with high activity levels in healthy plants at different developmental stages. The activ- ities of various AspAT isoenzymes have been found in dif- ferent tissues and different subcellular locations, such as the cytosol, mitochondria, chloroplasts, glyoxysomes or peroxisomes (Lam et al., 1996). The subcellular com- partmentalization of the AspAT isoenzymes suggest that the different forms of AspAT might serve distinct roles in plant metabolism. It is also important to note that individual AspAT isoenzymes respond differently to environmental conditions and metabolic status, such as light treatment or nitrogen starvation, which suggests that they serve distinct roles (Lam et al., 1996). It was observed in citrus that sick and stressed plants had highly reduced expression of AspAT. In the C3 plant Arabidopsis, the entire gene family of AspAT isoenzymes has been characterized (Schultz and Coruzzi, 1995) and five different AspAT cDNA clones [ASP1-4 and ASP5 (formally AAT1)] were obtained, in- cluding those encoding the mitochondrial, plastidic, pero- xisomal and cytosolic forms. Even though two of the five ASP genes encode cytosolic forms of AspAT (ASP2 and ASP4), only ASP2 is expressed at high levels, especially in roots (Schultz and Coruzzi, 1995), and this is probably the AspAT form found in citrus root. The ASP1 and ASP3 genes, which encode a mitochondrial and a peroxisomal form of AspAT, respectively, are each expressed at rela- tively high levels in all organs examined (Schultz and Coruzzi, 1995) and are probably the forms present in the other citrus tissues.
Mostrar mais

9 Ler mais

The Influence Of CSR Awareness On Consumer Purchase Decision Of A Telecommunication Network In Ghana A Case Of La Nkwantanag Madina Municipality

The Influence Of CSR Awareness On Consumer Purchase Decision Of A Telecommunication Network In Ghana A Case Of La Nkwantanag Madina Municipality

on overall company evaluations‖. Murray and Vogel (1997) have investigated the effect of associated CSR practices on consumers and presented similar findings. The CSR activities mentioned in the research are, for instance, environmental protection practices (energy conservation), engagement in acts to promote human welfare, corporate social marketing (electric safety education for schoolchildren), contribution to the economic development of the region, and consumer protection program. Their research found that CSR programs lead to improved customer attitudes towards the firm, including beliefs about the company‘s honesty, consumer responses, and increased support for the firm in labor or government disputes. Mohr et al. (2001) conducted a consumer interview project for investigating the impact of firms‘ CSR on consumer behavior. How well are consumers aware of the CSR level of individual firms? Are the purchase decisions of consumers affected by a firm‘s CSR, and how much? How do consumers think about firms‘ motivation for being socially responsible? Mohr et al. (2001) found that consumers are positive to business in general. It is not wrong to pursue economic interests. Consumers expect firms to be socially responsible. The attitudes of consumers toward socially responsible firms are more positive than toward irresponsible firms. Consumers are aware that socially responsible firms are helping themselves by practicing CSR. But this perception of consumers does not harm the positive consumer evaluations toward socially responsible firms. The study of Mohr et al. (2001) is enlightening for researchers, managers and policy makers. For managers specifically, it is clear that consumers do care about a firm‘s CSR and act accordingly. Some consumers are highly ethical in
Mostrar mais

9 Ler mais

Effects of model chemistry and data biases on stratospheric ozone assimilation

Effects of model chemistry and data biases on stratospheric ozone assimilation

analyses in GOATS. Adaptive photochemistry reduces the mismatches between ozone observations and the photochem- ical reference states (Fig. 15), which in turn reduce mean O−Fs (Fig. 14). Thus, as suggested by Geer et al. (2007), when the original photochemical reference states are biased high or low, adaptive photochemistry should improve ozone analyses at higher altitudes when assimilating largely unbi- ased ozone (and temperature) data. However, our results re- veal a disadvantage of adaptive photochemistry when assim- ilating biased ozone data. In this case, the adaptive photo- chemistry incorporates this observational bias into its refer- ence states (Fig. 15), and hence into the ozone forecasts, so that the final ozone analysis fields retain some of the obser- vational biases (Fig. 14). By contrast, earlier GOATS ex- periments that used an internal unbiased photochemical ref- erence state were able to correct these observational biases during the forecast stage to yield a more unbiased ozone analysis (see Figs. 7, 8a and 14). Thus, systems continu- ally assimilating ozone and temperature data that are prone to sudden offsets or slow drifts may be better off using non- adaptive photochemistry to maintain forecast reliability, and using mean O−Fs to monitor the system for these input data biases as in Fig. 14. On the other hand, systems assimilat- ing ozone and temperature data whose precision and accu- racy are both high and stable may benefit by using adaptive photochemistry schemes. All these results reinforce the gen- eral point made by Geer et al. (2007) and others (e.g., Rood, 2005; Dee, 2005) that biases in either the ozone observations or the ozone forecast model can affect the performance of an ozone assimilation system.
Mostrar mais

19 Ler mais

Turbulent viscosity optimized by data assimilation

Turbulent viscosity optimized by data assimilation

The eciency of the optimal control method to optimize time-constant viscosity distributions in 1-D vertical models has already been underlined (Yu and O'Brien, 1991; Panchang and Richardson, 1993). In these studies, initial and boundary conditions are assumed to be well known, the variational formulation of the dynamic model acting as a strong constraint. In the case of 1-D advection-di€usion equation (Leredde et al., 1998) it has been shown that, with such a strong constraint formulation, the simultaneous optimization of the initial conditions, the boundary conditions and the space and time distributed viscosity coecient becomes rather dicult. This is due to the fact that a single solution for all the controls is not ensured if no penalization of the ®rst guesses of the controls is included in the cost function. Instead of using this type of strong constraint formulation, Eknes and Evensen (1997) have developed a weak constraint formulation which allows the observational data, the turbulent vertical viscosity, the initial and boundary conditions and also the model equations to be a€ected by errors. This approach involves a sophisticated iterative representer method (Bennett, 1992) and generates a highly non-linear prob- lem whose solution depends on the required ®rst guesses of the control and the error weights. Eknes and Evensen (1997) have used a 1-D Ekman model which is only an approximation of the primitive equations. Their results indicate that model de®ciencies, such as neglected physics, are accounted for through the weak constraint formulation to ensure an inverse solution in agreement with the measurements. In this respect and in the framework of this non-exact model, their ®t is closer to the data than those obtained by the strong constraint formulation (Yu and O'Brien, 1991).
Mostrar mais

15 Ler mais

Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland

Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland

The compacted snow (firn) found in the accumulation zone of the major ice sheets acts as a unique archive of old air, preserving a continuous record of atmospheric composition from the present up to a century back in time (Battle et al., 1996). Sampling of this archive has allowed for reconstruc- tion of the recent atmospheric history of many trace gas species (e.g. Butler et al., 1999; Sturrock et al., 2002; Ay- din et al., 2004; Montzka et al., 2004; Assonov et al., 2007; Martinerie et al., 2009) and their isotopologues (e.g. Francey et al., 1999; Ferretti et al., 2005; Bernard et al., 2006). Be- cause of its temporal range it naturally bridges the age gap between direct atmospheric observations and the ice core record (Etheridge et al., 1998). Firn air analysis has some significant advantages over the ice core technique. First, firn air can be sampled directly using a pumping line (Schwan- der et al., 1993), making an ice extraction step unneces- sary. Second, large sample sizes can be obtained making this method very suited for studying, e.g. recent changes in the isotopic composition of trace gases (Sugawara et al., 2003; R¨ockmann et al., 2003; Ishijima et al., 2007). Third, because bubble occlusion introduces additional smoothing, firn air records can achieve higher temporal resolution than ice cores (Trudinger et al., 2004).
Mostrar mais

19 Ler mais

Uncertainty in geological and hydrogeological data

Uncertainty in geological and hydrogeological data

One of the great and very general challenges within the hy- drological science is to understand the impact of changing scales on various process descriptions and parameter values. The average volume of hydrogeological measurements (also named support volume) is ranging many orders of magnitude depending on the size of volume representing the individual measurements. Spatial heterogeneity as a function of scale is well documented in the literature for saturated hydraulic con- ductivity (Clauser, 1992, S´anchez-Vila et al., 1996; Nilsson et al., 2001). Values of the saturated hydraulic conductivity depend on the volume of substrate sampled by the applied hydraulic testing method. A literature example in coarse- grained fluvial sediments (Bradbury and Muldoon, 1990) is shown in Fig. 2. It is evident that the mean hydraulic conduc- tivity increases as the support volume of the tests increases.
Mostrar mais

11 Ler mais

Hydrological real-time modelling in the Zambezi river basin using satellite-based soil moisture and rainfall data

Hydrological real-time modelling in the Zambezi river basin using satellite-based soil moisture and rainfall data

The performance of the model running in the determinis- tic mode is illustrated in Fig. 5 and compared to the refer- ence method. The modeled discharge agrees in general quite well with the measured flows. For all the applied models the root mean squared error (RMSE) and the Nash-Sutcliffe efficiency are calculated (Tables 2 and 3). The model devel- oped gives better results than the reference method for the Upper Zambezi and the Kafue River basin where both the Nash-Sutcliffe efficiency and the RMSE are slightly higher or lower, respectively. It is clearly visible that the flood maxima are reproduced much better than in the reference method. Obviously the inclusion of rainfall information is most beneficial for the maxima as the correlation between BWI and rainfall deteriorates for large precipitation events. However, for the Luangwa river the model performance was not satisfactory when running in the deterministic mode. It even showed a slightly poorer performance than the reference method which also does not allow for adequate modelling of the situation.
Mostrar mais

10 Ler mais

Influence of supply voltage frequency of induction coil on inoculation efficiency of pure aluminium structure

Influence of supply voltage frequency of induction coil on inoculation efficiency of pure aluminium structure

On the basis of conducted analysis of studies results was affirmed, that rotate electromagnetic field generated by induction coil fed with frequency of supply voltage larger than power network, influences on liquid metal in time of its solidification in mould, guarantees refinement of structure of pure Al without necessity of application of inoculants sort Ti and B. This method of inoculation is important, because Ti and B decrease the degree of purity and electrical conductivity of pure aluminium. Moreover Ti and B are reason of point cracks formation during rolling of ingots. This method of inoculation was been possible to apply in conditions of continuous casting because allows on producing of ingots from aluminium about purity 99,5% with structure without columnar crystals, which are unfavourable from point of view of usable properties.
Mostrar mais

6 Ler mais

Product carbon footprints and their uncertainties in comparative decision contexts.

Product carbon footprints and their uncertainties in comparative decision contexts.

Already in the 1990s were dispersion estimates made for a number of LCI related emission parameters [16,17]. Around the same time, there were also several new methodologies sug- gested for how to include quantitative uncertainties in life cycle inventories (LCIs)[18–21]. To date, however, the uncertainties considered have largely been limited to sensitivity analyses [22], default inventory ranges [23,24], characterization factors for one specific impact category [25,26], or pedigree estimates [27,28]. Pedigree estimates refer to a matrix of data quality indi- cators which evaluate the representativeness of the data used, which later are tentatively quanti- fied using uncertainty factors based upon expert judgment or empirical data [27,29,30]. Statistical testing of outcomes, in the meantime, is rare among LCA studies, and where con- sulted it is largely limited to quotients (A/B) [31]. Table 1 summarizes a selection of LCA stud- ies that take uncertainty into account. The table results show that this is the first study that evaluates empirical LCI uncertainty data, empirical LCIA uncertainty data, in a comparative analysis applying Monte Carlo dependent sampling and a hypothesis based significance test. It is our belief that failure to explicitly and properly deal with uncertainties may result in counterproductive decisions, and that more extensive guidelines will merely reduce the number
Mostrar mais

11 Ler mais

Better constraints on the sea-ice state using global sea-ice data assimilation

Better constraints on the sea-ice state using global sea-ice data assimilation

close to each other. Furthermore, these simulations show the same large scale geo- graphical distribution of ice thickness. However, during ON07, as for the MA07 cam- paign (Figs. 8, 7), ice is thinner in the centre of the Arctic Basin, by up to 70 cm near the North Pole (unobserved area due to satellite orbit) (Fig. 6b, d). The intrusion of thick sea ice in the Beaufort sea is also less pronounced in FB, which is more realistic.

41 Ler mais

The modification process of AlSi21CuNi silumin and its effect on change of mechanical properties of the alloy

The modification process of AlSi21CuNi silumin and its effect on change of mechanical properties of the alloy

Pouring temperature belongs to very important factors in obtainment of correct results of the modification. Hypereutectoid silumins are characteristic of good castability even in temperatures close to liquidus curve, what suggests implementation of low temperature of casting. However, such method of casting creates conditions to easy coarsening of primary crystals of silicon and their non-uniform distribution on microstructure of the casting. Rate of cooling of the alloy poured into mould has also an effect on results of the modification.
Mostrar mais

4 Ler mais

Show all 10000 documents...