Simultaneous Assimilation Research Articles

Inverse modelling of European N<sub>2</sub>O emissions: assimilating observations from different networks

Abstract. We describe the setup and first results of an inverse modelling system for atmospheric N2O, based on a four-dimensional variational (4DVAR) technique and the atmospheric transport zoom model TM5. We focus in this study on the European domain, utilizing a comprehensive set of quasi-continuous measurements over Europe, complemented by N2O measurements from the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration (NOAA/ESRL) cooperative global air sampling network. Despite ongoing measurement comparisons among networks parallel measurements at a limited number of stations show that significant offsets exist among the different laboratories. Since the spatial gradients of N2O mixing ratios are of the same order of magnitude as these biases, the direct use of these biased datasets would lead to significant errors in the derived emissions. Therefore, in order to also use measurements with unknown offsets, a new bias correction scheme has been implemented within the TM5-4DVAR inverse modelling system, thus allowing the simultaneous assimilation of observations from different networks. The N2O bias corrections determined in the TM5-4DVAR system agree within ~0.1 ppb (dry-air mole fraction) with the bias derived from the measurements at monitoring stations where parallel NOAA discrete air samples are available. The N2O emissions derived for the northwest European and east European countries for 2006 show good agreement with the bottom-up emission inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Moreover, the inverse model can significantly narrow the uncertainty range reported in N2O emission inventories for these countries, while the lack of measurements does not allow to reduce the uncertainties of emission estimates in southern Europe. Several sensitivity experiments were performed to test the robustness of the results. It is shown that also inversions without detailed a priori spatio-temporal emission distributions are capable to reproduce major regional emission patterns within the footprint of the existing atmospheric network, demonstrating the strong constraints of the atmospheric observations on the derived emissions.

Assimilation of multiresolution radiation products into a downwelling surface radiation model: 2. Posterior ensemble implementation

Satellite‐derived radiation products are used to condition a high‐resolution estimate (space and time) of total downwelling radiation within a data assimilation (DA) framework. The prior ensemble (part 1 of this study) is conditioned using existing, multiresolution radiation products in an ensemble‐based DA scheme to yield a high‐resolution posterior ensemble. The resulting posterior ensemble implicitly captures the complex spatiotemporal uncertainties inherent in satellite‐derived radiative flux estimation. In addition, application of the DA framework reduces these uncertainties while simultaneously downscaling coarse‐scale spatial information content from the existing, multiresolution radiation products. Results suggest that the magnitude of the gain matrix is greatest when longwave (LW) estimates assimilate LW measurements and shortwave (SW) estimates assimilate SW measurements. Correlations in space are less pronounced between broadband fluxes of different type. The greatest reduction in uncertainty was achieved via simultaneous assimilation of North American Land Data Assimilation–LW and Pinker‐SW products. Comparison of the conditioned posterior ensemble against a network of independent, ground‐based radiometer observations in the Southern Great Plains of the United States during the 14 month study period showed a maximum reduction of 8 W m−2 (∼32%) in LW uncertainty and 2 W m−2 (∼6%) in SW uncertainty. The posterior (conditioned) ensemble could eventually be used as forcing in distributed terrestrial hydrologic model applications or land data assimilation systems with the goal of better understanding and characterizing the variability and uncertainty of the hydrologic response at the land surface.

Timescales of magma differentiation from basalt to andesite beneath Hekla Volcano, Iceland: Constraints from U-series disequilibria in lavas from the last quarter-millennium flows

Measurements of 238U– 230Th– 226Ra disequilibria, Sr–Nd–Pb–Hf isotopes and major-trace elements have been conducted for lavas erupted in the last quarter-millennium at Hekla volcano, Iceland. The volcanic rocks range from basalt to dacite. Most of the lavas (excluding dacitic samples) display limited compositional variations in radiogenic Sr–Nd–Pb–Hf isotopes ( 87Sr/ 86Sr = 0.70319–0.70322; 143Nd/ 144Nd = 0.51302–0.51305; 206Pb/ 204Pb = 19.04–19.06; 207Pb/ 204Pb = 15.53–15.54; 208Pb/ 204Pb = 38.61–38.65; 176Hf/ 177Hf = 0.28311–0.28312). All the samples possess ( 230Th/ 238U) disequilibrium with 230Th excesses, and they show systematic variations in ( 230Th/ 232Th) and ( 238U/ 232Th) ratios. The highest 226Ra excesses occur in the basalt and most differentiated andesite lavas, while some basaltic-andesite lavas have ( 226Ra/ 230Th) ratio that are close to equilibrium. The 238U– 230Th– 226Ra disequilibria variations cannot be produced by simple closed-system fractional crystallization with radioactive decay of 230Th and 226Ra in a magma chamber. A closed-system fractional crystallization model and assimilation and fractional crystallization (AFC) model indicate that the least differentiated basaltic andesites were derived from basalt by fractional crystallization with a differentiation age of ∼24 ± 11 kyr, whereas the andesites were formed by assimilation of crustal material and fractionation of the basaltic-andesites within 2 kyr. Apatite is inferred to play a key role in fractionating the parent–daughter nuclides in 230Th– 238U and 226Ra– 230Th to make the observed variations. Our proposed model is that several batches of basaltic-andesite magmas that formed by fractional crystallization of a basaltic melt from a deeper reservoir, were periodically injected into the shallow crust to form individual magma pockets, and subsequently modifying the original magma compositions via simultaneous assimilation and fractional crystallization. The assimilant is the dacitic melt, which formed by partial melting of the crust.

Simultaneous shape-contrast and global assimilation effects in the perception of aspect ratio

Simultaneous shape-contrast and global assimilation effects in the perception of aspect ratio

Particle filters for structural system identification using multiple test and sensor data: A combined computational and experimental study

The problem of structural system identification when measurements originate from multiple tests and multiple sensors is considered. An offline solution to this problem using bootstrap particle filtering is proposed. The central idea of the proposed method is the introduction of a dummy independent variable that allows for simultaneous assimilation of multiple measurements in a sequential manner. The method can treat linear/nonlinear structural models and allows for measurements on strains and displacements under static/dynamic loads. Illustrative examples consider measurement data from numerical models and also from laboratory experiments. The results from the proposed method are compared with those from a Kalman filter-based approach and the superior performance of the proposed method is demonstrated. Copyright (C) 2009 John Wiley & Sons, Ltd.

Soil model parameter estimation with ensemble data assimilation

AbstractA parameter estimation problem in context of ensemble data assimilation is addressed. In an example using a one‐point soil temperature model, the parameters corresponding to the emissivity and to the effective depth between the surface and the lowest atmospheric model level are estimated together with the initial conditions for temperature. The nonlinear synthetic observations representing various fluxes are assimilated using the Maximum Likelihood Ensemble Filter (MLEF). The results indicate a benefit of simultaneous assimilation of initial conditions and parameters. The estimated uncertainties are in general agreement with actual uncertainties. Copyright © 2009 Royal Meteorological Society

A multi-component data assimilation experiment directed to sulphur dioxide and sulphate over Europe

Fine particulate matter (PM) is relevant for human health and its components are associated with climate effects. The performance of chemistry transport models for PM, its components and precursor gases is relatively poor. The use of these models to assess the state of the atmosphere can be strengthened using data assimilation. This study focuses on simultaneous assimilation of sulphate and its precursor gas sulphur dioxide into the regional chemistry transport model LOTOS–EUROS using an ensemble Kalman filter. The process of going from a single component setup for SO 2 or SO 4 to an experiment in which both components are assimilated simultaneously is illustrated. In these experiments, solely emissions, or a combination of emissions and the conversion rates between SO 2 and SO 4 were considered uncertain. In general, the use of sequential data assimilation for the estimation of the sulphur dioxide and sulphate distribution over Europe is shown to be beneficial. However, the single component experiments gave contradicting results in direction in which the emissions are adjusted by the filter showing the limitations of such applications. The estimates of the pollutant concentrations in a multi-component assimilation have found to be more realistic. We discuss the behavior of the assimilation system for this application. The model uncertainty definition is shown to be a critical parameter. The increased complexity associated with the simultaneous assimilation of strongly related species requires a very careful specification of the experiment, which will be the main challenge in the future data assimilation applications.

Data assimilation in a system with two scales—combining two initialization techniques

An ensemble Kalman filter (EnKF) is used to assimilate data onto a non-linear chaotic model, coupling two kinds of variables. The first kind of variables of the system is characterized as large amplitude, slow, large scale, distributed in eight equally spaced locations around a circle. The second kind of variables are small amplitude, fast, and short scale, distributed in 256 equally spaced locations. Synthetic observations are obtained from the model and the observational error is proportional to their respective amplitudes. The performance of the EnKF is affected by differences in the spatial correlation scales of the variables being assimilated. This method allows the simultaneous assimilation of all the variables. The ensemble filter also allows assimilating only the large-scale variables, letting the small-scale variables to freely evolve. Assimilation of the large-scale variables together with a few small-scale variables significantly degrades the filter. These results are explained by the spurious correlations that arise from the sampled ensemble covariances. An alternative approach is to combine two different initialization techniques for the slow and fast variables. Here, the fast variables are initialized by restraining the evolution of the ensemble members, using a Newtonian relaxation toward the observed fast variables. Then, the usual ensemble analysis is used to assimilate the large-scale observations.

Digital Game Involvement

This article proposes a conceptual model for understanding game involvement and immersion on a variety of experiential dimensions corresponding to six broad categories of game features. The article ends with a proposal to replace the metaphor of immersion with one of incorporation. This reconceptualization seeks to replace the unidirectional plunge of player into game space implied by the term immersion with one of simultaneous assimilation of the digital environment and presence to others within it.

Simulating Visual Pattern Detection and Brightness Perception Based on Implicit Masking

A quantitative model of implicit masking, with a front-end low-pass filter, a retinal local compressive nonlinearity described by a modified Naka-Rushton equation, a cortical representation of the image in the Fourier domain, and a frequency-dependent compressive nonlinearity, was developed to simulate visual image processing. The model algorithm was used to estimate contrast sensitivity functions over 7 mean illuminance levels ranging from 0.0009 to 900 trolands, and fit to the contrast thresholds of 43 spatial patterns in the Modelfest study. The RMS errors between model estimations and experimental data in the literature were about 0.1 log unit. In addition, the same model was used to simulate the effects of simultaneous contrast, assimilation, and crispening. The model results matched the visual percepts qualitatively, showing the value of integrating the three diverse perceptual phenomena under a common theoretical framework.

Petrogenesis of the Kunavaram alkaline complex and the tectonothermal evolution of the neighboring Eastern Ghats Belt granulites, SE India

Geochemical and geochronological study of the Kunavaram alkaline rocks near the craton–Eastern Ghats Belt (EGB) contact in SE India indicates that alkaline magma was emplaced at ∼1384Ma along a NE–SW Mesoproterozoic rift at the cratonic margin. This paleo-rift can be delineated by the several Mesoproterozoic alkaline intrusives at the cratonic margin (e.g. Khariar, Kunavaram, Jojuru, Elchuru and others). The geochemical variations in the Kunavaram alkaline suite can be explained by an assimilation-fractional crystallization (AFC) process dominated by the fractionation of clinopyroxene–amphibole, apatite, titanite, zircon and allanite and the simultaneous assimilation of bulk upper crustal material from the craton. The alkaline complex and other craton margin rocks and the marginal granulites of the EGB were overprinted by an amphibolite facies tectonothermal event during the Neoproterozoic–Paleozoic (611–484Ma) when Pan-African tectonism thrust the EGB granulites westward over the cratonic foreland along a number of northwest-vergent shear zones. The Pan-African thrust stacking has the cratonic boundary and the alkaline rocks in the footwall and the EGB granulites in the hanging wall. The continuous nature of the Pan-African shear fabric across the craton–EGB contact near Kunavaram implies that the two crustal segments shared a common boundary during the Neoproterozoic–Paleozoic. Prior to the Pan-African event, the evolutionary history of the EGB is characterized by the presence of an early Neoproterozoic (1017–1087Ma) granulite-facies tectonometamorphic overprint during the Grenvillian orogeny, evidence for which is lacking in the alkaline and other craton margin rocks. The craton–EGB contact thus represents a rifted Mesoproterozoic margin deformed during Pan-African collisional tectonics.

Energy‐constrained open‐system magmatic processes 3. Energy‐Constrained Recharge, Assimilation, and Fractional Crystallization (EC‐RAFC)

Geochemical data for igneous rock suites provide conclusive evidence for the occurrence of open‐system processes within thermally and compositionally evolving magma bodies. The most significant processes include magma Recharge (with possible enclave formation and magma mixing), Assimilation of anatectic melt derived from wallrock partial melting and formation of cumulates by Fractional Crystallization (RAFC). In this study, we extend the Energetically Constrained Assimilation and Fractional Crystallization (EC‐AFC) model [Spera and Bohrson, 2001; Bohrson and Spera, 2001] to include the addition of compositionally and thermally distinct recharge melt during simultaneous assimilation and fractional crystallization. Energy‐Constrained Recharge, Assimilation, and Fractional Crystallization (EC‐RAFC) tracks the trace element and isotopic composition of melt, cumulates and enclaves during simultaneous recharge, assimilation and fractional crystallization. EC‐RAFC is formulated as a set of 3 + t + i + s coupled nonlinear differential equations, where the number of trace elements and radiogenic and stable isotope ratios modeled are t, i, and s, respectively. Solution of the EC‐RAFC equations provides values for the average wallrock temperature (Ta), mass of melt within the magma body (Mm), mass of cumulates (Mct) and enclaves (Men), mass of wallrock involved in the thermal interaction (Mao), mass of anatectic melt assimilated (M*a), concentration of t trace elements and i + s isotopic ratios in melt (Cm), cumulates (Cct), enclaves (Cen), and anatectic melt (Ca) as a function of magma temperature (Tm). Input parameters include the equilibration temperature (Teq), the initial temperature and composition of pristine melt (Tmo, Cmo, εmo), recharge melt (Tro, Cro, εro), and wallrock (Tao, Cao, εao), temperature‐dependent trace element distribution coefficients (Dm, Dr, Da), heats of transition for wallrock (Δha), pristine melt (Δhm), and recharge melt (Δhr), and the isobaric specific heat capacity of assimilant (Cp,a), pristine melt (Cp,m), and recharge melt (Cp,r). The magma recharge mass function, Mr(Tm), is specified a priori and defines how recharge magma is added to standing magma. The present EC‐RAFC simulator incorporates a weak coupling to major element mass balance and phase relations based on laboratory experiments or Gibbs Energy minimization [e.g., Ghiorso, 1997]. EC‐RAFC can be applied to a variety of magmatic systems including volcanic suites that show evidence of magma mixing, layered mafic intrusions, and granitoid plutons. Predictions for masses, as well as compositions of magmatic products, are part of the EC‐RAFC solution. The “systems” approach provides an opportunity to quantitatively assess the roles of assimilation, fractional crystallization, and magma recharge in magma evolution using trace element and isotopic constraints together with energy conservation.

The petrogenesis of Tertiary cone-sheets in Ardnamurchan, NW Scotland: petrological and geochemical constraints on crustal contamination and partial melting

Abundant cone sheets form one of the last magmatic stages in the Tertiary central complex on the Scottish peninsula of Ardnamurchan and can be grouped into a younger inner and an older outer suite relative to a gabbro intrusion. Most of the cone-sheets consist of tholeiitic to transitional basalt with MgO contents between 7.5% and 4%, although more evolved rocks also occur (to 0.5% MgO). The mafic samples are slightly enriched in the light rare earth elements (Chondrite-normalized La/Sm ∼1.1), the enrichment increases in the more evolved rocks. The compositional variation of the basaltic rocks is mainly due to crystal fractionation of olivine and clinopyroxene at depths of ∼10 km but trace elements show simultaneous assimilation of Archean Lewisian granulite crust. The andesitic to rhyolitic lavas formed by fractional crystallization from the contaminated basaltic magma coupled with assimilation of Proterozoic Moine metasediments at uppermost crustal levels. The occurrence of composite cone-sheets with basaltic and rhyolitic parts and mixtures between these magmas implies that the melts ascended successively but within a short period of time. The parental magmas of the Ardnamurchan cone-sheets must have formed at relatively shallow depths in the mantle and are comparable to the youngest tholeiitic lavas from the neighbouring island of Mull.

Simultaneous assimilation and contrast effects in judgments of self and others.

Simultaneous assimilation and contrast effects in judgments of self and others.

Sr, Nd, and Pb isotope systematics of granitic rocks in the central Ogcheon Belt, Korea.

The source characteristics and magmatic evolution history of granitic rocks in the central Ogcheon Belt, Korea, were investigated based upon Sr-Nd-Pb isotope systematics. The granitic rocks are divided into three types; the Permian to Triassic granites distributed near the Boeun area (PTG), the Daebo granitic batholith (DBG), and Cretaceous Sogrisan Granite (SOGR). Well fitted Rb-Sr whole rock isochrons of the PTG yield geologically significant ages (256 Ma for the Baegrock Granodiorite (BRGD), 230 Ma for the Boeun Granite (BOGR), and 216 Ma for the Chungsan Granite (CHGR)). Rb-Sr isotope data of the DBG do not form isochrons of geologically reasonable ages, suggesting that the batholith was formed by discrete magmatic events. Variation of initial Sr and Nd isotope ratios in the PTG can be explained by a simultaneous assimilation and fractional crystallization (AFC) model. The BRGD has the most primitive Sr-Nd-Pb isotopic signature among the PTG. Based on mass balance calculation, the relatively high but strongly negative eNd(t) of the BRGD is difficult to explain by an interaction of mantle-derived melt with crustal materials. Field observation and low initial 87Sr/86Sr ratios of the BRGD contradict the possibility of its derivation exclusively from the upper crustal source region. The isotopic signature of the BRGD is taken to be largely inherited from the continental lower crust. Primitive BRGD samples have relatively higher eNd(t) values than the other granites, indicating that the crustal formation age of the lower crust is younger than that of the upper crust. Less radiogenic Sr and Pb isotope ratios of the BRGD indicate that Rb, U, and Th (and other large ion lithophile elements ?) depletion has been maintained in the lower crust for a geologically long time. eNd(t) values of the DBG are strongly related to their locality, indicating local heterogeneity in the source region. Inconsistent variation of the DBG in eNd(t) vs. eSr(t) plot precludes a mixing model between primitive melt and upper crustal materials. Relatively constant eNd(t) and variable esr(t) of the SOGR reflects the effect of simultaneous assimilation and fractional crystallization of feldspars. Ranges of initial Sr, Nd and Pb isotopic compositions of the SOGR are quite similar to those of the other, older granites, which implies a similarity of source materials between them.

Simultaneous assimilation and contrast effects in judgments of self and others.

Judgments of self and referent others tend to be positively related, as evident in the false consensus effect, but others may also be contrasted from the self, as noted in the false uniqueness literature. In 3 studies that examined the domains of attitudes and traits, evidence of both assimilative and contrastive associations between self- and other-judgements were noted, depending on the form of judgment (objective vs. subjective) and the relevant judgment scale anchor (self vs. others). When self-judgments were made first, objective appraisals of reference groups were contrasted from subjective self-appraisals (after controlling for individual differences in participants' behavioral reports). When judgments of others were made first, objective self-ratings were contrasted from subjective other-judgments. Implications for the false consensus literature and the shifting standards model (M. Biernat, M. Manis, & T. E. Nelson, 1991) are discussed.

Successive Correction of the Mean Sea Surface Height by the Simultaneous Assimilation of Drifting Buoy and Altimetric Data

Abstract A simultaneous assimilation model of drifting buoy and altimetric data is proposed to determine the mean sea surface height (SSH) as well as the temporal evolution of the surface circulation on synoptic scales. To demonstrate the efficiency of our assimilation model, several identical twin experiments for the double-gyre circulation system are performed using a 11/2-layer primitive equation model. An optimal interpolation for the multivariate is used for the assimilation scheme that assumes the geostrophic relationship between the error fields of the velocity and the interface depth. To identify the nature of the assimilation of the buoy-derived velocities into the dynamical ocean model, the authors first conduct the assimilation experiment using the drifting buoy data alone. The result shows that realistic buoy deployment (32 in a 40° square) can effectively constrain the model variables; that is, both the absolute (mean plus time varying) velocity and SSH (interface depth) fields are significan...

Inorganic Carbon-Stimulated O2 Photoreduction Is Suppressed by NO2- Assimilation in Air-Grown Cells of Synechococcus UTEX 625.

The effect of NO2- assimilation on O2 exchange and CO2 fixation of the cyanobacterium, Synechococcus UTEX 625, was studied mass spectrometrically. Upon addition of 1 mM inorganic carbon to the medium, inorganic carbon pools developed and accelerated O2 photoreduction 5-fold when CO2 fixation was inhibited. During steady-state photosynthesis at saturating light, O2 uptake represented 32% of O2 evolution and balanced that portion of O2 evolution that could not be accounted for by CO2 fixation. Under these conditions, NO2- assimilation reduced O2 uptake by 59% but had no influence on CO2 fixation. NO2- assimilation decreased both CO2 fixation and O2 photoreduction at low light and and increased net O2 evolution at all light intensities. The increase in net O2 evolution observed during simultaneous assimilation of carbon and nitrogen over carbon alone was due to a suppression of O2 photoreduction by NO2- assimilation. When CO2 fixation was precluded, NO2- assimilation inhibited O2 photoreduction and stimulated O2 evolution. When the electron supply was limiting (low light), competition among O2, CO2, and NO2- for electrons could be observed, but when the electron supply was not limiting (saturating light), O2 photoreduction and/or NO2- reduction caused electron transport that was additive to that for maximum CO2 fixation.

Feasibility of AFC models for the petrogenesis of calc-alkaline magma series

One of the most popular petrogenetic concepts is that of simultaneous assimilation and fractional crystallisation (AFC). The equations governing these processes are well known and widely applied. The power and attraction of the model are that, with the minimum of constraints, petrogenetic schemes can be erected for essentially any group of rocks. These models are usually based on the observed variations in a small number of trace elements and/or isotopic systems. In this paper we have generated well-constrained AFC models for the Variscan, calc-alkaline Querigut complex in the French Pyrenees. Our models are based on geological constraints on the identities of the parent magma and candidate assimilants, and the Sm-Nd and Rb-Sr isotope systematics of the rocks. The modelling is successful in mimicking the isotope array for the actual rocks. However, the results are massively inconsistent with those produced using the major- and trace-element concentrations. Our major conclusion is that AFC modelling should be undertaken only with robust initial constraints on the compositions of the parent magma and the proposed assimilant, with due respect for crystal-liquid partition coefficients, in so far as they are known. The results should then be accepted only if the isotope-based model parameters are consistent with those derived from major- and trace-element variations.

Photosynthetic Nitrite Reduction as Influenced by the Internal Inorganic Carbon Pool in Air-Grown Cells of Synechococcus UTEX 625.

Photosynthetic reduction of NO2- was studied in air-grown cells of a cyanobacterium, Synechococcus UTEX 625. Addition of NO2- resulted in significant amounts of chlorophyll a fluorescence quenching both in the absence and presence of CO2, fixation inhibitors, glycolaldehyde or iodoacetamide. The degree of NO2- quenching was insensitive to the O2 concentration in the medium. Addition of 100 [mu]M inorganic carbon in the presence of glycolaldehyde and O2, leading to formation of the carbon pool within the cells, resulted in pronounced fluorescence quenching. Removal of O2 from the medium restored the fluorescence yield completely, and the subsequent addition of NO2- quenched 36% of the variable fluorescence. From the response to added 3-(3,4-dichlorophenyl)-1,1-dimethylurea, the quenching by NO2- appeared to be photochemical quenching, and nonphotochemical quenching did not seem to be present. The reduction of NO2- observed on its addition to inorganic carbon-depleted cells remained uninfluenced by O2 or glycolaldehyde. The internal inorganic carbon pool in the cells stimulated NO2- reduction, both in the presence and absence of O2, by 4.8-fold. An increase in NO2- reduction by 0.5-fold was also observed in the presence of O2 during simultaneous assimilation of carbon and nitrogen in inorganic carbon-depleted cells. Contrary to this, under anaerobiosis, NO2- reduction was suppressed when carbon and nitrogen assimilation occurred together.