A Time Monte Carlo method for addressing uncertainty in land-use change models

One of the main objectives of land-use change models is to explore future land-use patterns. Therefore, the issue of addressing uncertainty in land-use forecasting has received an increasing attention in recent years. Many current models consider uncertainty by including a randomness component in their structure. In this paper, we present a novel approach for tuning uncertainty over time, which we refer to as the Time Monte Carlo (TMC) method. The TMC uses a specific range of randomness to allocate new land uses. This range is associated with the transition probabilities from one land use to another. The range of randomness is increased over time so that the degree of uncertainty increases over time. We compare the TMC to the randomness components used in previous models, through a coupled logistic regression-cellular automata model applied for Wallonia (Belgium) as a case study. Our analysis reveals that the TMC produces results comparable with existing methods over the short-term validation period (2000–2010). Furthermore, the TMC can tune uncertainty on longer-term time horizons, which is an essential feature of our method to account for greater uncertainty in the distant future.     

Luftelektrische Tagesgänge und Massenaustausch im Hochgebirge der Alpen

Zusammenfassung Es wird über die Ergebnisse luftelektrischer Untersuchungen auf dem Jungfraujoch (Schweiz) und ihre Deutung berichtet. Während zweier Meßperioden von je mehrwöchiger Dauer wurden das luftelektrische Potentialgefälle und der vertikale Leitungsstrom registriert; bearbeitet sind zunächst die Tagesgänge an klaren Tagen mit Hochdruckwetter. Die Tagesvariationen der drei luftelektrischen Elemente: Potentialgefälle, Vertikalstrom und Leitfähigkeit zeigen, daß auf dem Jungfraujoch im Sommer und im Herbst zwei ganz verschiedene Typen des luftelektrischen Verhaltens zu erkennen sind: Im Sommer herrscht auch an dieser Höhenstation der von den Tieflandstationen bekannte Typ vor, bei dem das Potentialgefälle angenähert invers zur Leitfähigkeit und zum Vertikalstrom verläuft. Im Herbst dagegen verlaufen Potentialgefälle und Vertikalstrom im wesentlichen gleichsinnig bei gegensinniger, aber schwächer ausgeprägter Tagesvariation der Leitfähigkeit. Im Sommer herrscht also auch in Jungfrauhöhe in den Alpen derkontinentale Typ, während sich im Herbst die Verhältnisse demozeanischen Typ annähern. Eine genauere Analyse ergibt, daß im Sommer die Tagesvariation desSäulenwiderstandes (columnar resistance) über dem Jungfraujoch in enger Korrelation zum örtlichen Widerstand der Luft an der Meßstelle (Reziprokwert der Leitfähigkeit) steht, während dies im Herbst nicht mehr der Fall ist.Zur Deutung dieser Feststellungen ist folgendes anzunehmen: Im Hochsommer wirkt die Tagesschwankung des vertikalen Massenaustausches aerosolverändernd bis in die Höhe des Alpenkammes, erkennbar daran, daß die Steuerung der luftelektrischen Tagesvariationen im wesentlichen von den unteren Schichten her erfolgt. Im Herbst dagegen ist dieser Einfluß in Kammhöhe der Alpen nahezu geschwunden; die Austauschvariation dringt nicht mehr bis in diese Höhen vor. Die verbleibenden Variationen der Leitfähigkeit deuten auf advektiven Luftaustausch hin. Das Verhalten des Dampfdruckes auf dem Jungfraujoch im Sommer und Herbst stützt diese Deutung.

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Summary The present paper gives an account of researches on atmospheric electricity carried out at Jungfraujoch (Switzerland). During two periods of several weeks each the potential gradient and the vertical air-earth current have been recorded. In the first place the diurnal variations on fine days at high pressure weather situation are elaborated. The daily variations of the three elements: potential gradient, vertical current, and conductivity, show that in summer and autumn two different types of the conditions of atmospheric electricity can be discerned: In summer the well-known type of the lowland stations is predominating also at this high altitude station, the type where the potential gradient is very nearly inverse to conductivity and vertical current. In autumn on the contrary the potential gradient and the vertical current are essentially parallel since the conductivity shows a slight diurnal variation in contrary sense. Thus, in summer prevails at the altitude of Jungfraujoch in the Alps thecontinental type, whilst in autumn the conditions approach to theoceanic type. It results from a rigorous analysis that in summer the diurnal variation of thecolumnar resistance on Jungfraujoch is in close correlation to the local air resistance (the reciprocal figure of conductivity) at the measuring point, whereas in autumn this is no longer the case.To explain these results we must assume as follows: In midsummer the diurnal variation of vertical mass exchange produces alterations of the aerosol up to the altitude of the crest of the Alps, which is perceptible from the fact that diurnal variations of atmospheric electricity start essentially from the lower layers. In autumn this influence has almost disappeared in the summit altitude of the Alps, as the daily variation of exchange does not advance to this altitude. The remaining variations of the conductivity point at an advective exchange of air. The behaviour of vapour pressure in summer and autumn at Jungfraujoch gives support to this interpretation.

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Résumé L'article traite des résultats de recherches d'électricité atmosphérique au Jungfraujoch (Suisse) et de leur interprétation. Deux périodes de mesures de plusieurs semaines chacune ont été consacrées à l'enregistrement du gradient de potentiel et du courant vertical. On décrit tout d'abord la variation diurne lors des jours sereins de temps anticyclonique. On distingue an Jungfraujoch en été et en automne respectivement deux types très différents de la marche diurne du gradient de potentiel, du courant vertical et de la conductibilité. En été le type bien connu des stations de plaine pour lequel le gradient de potentiel varie à peu près inversement à la conductibilité et au courant vertical s'observe aussi au Jungfraujoch. Par contre en automne le gradient de potentiel et le courant vertical varient en général dans le même sens, tandis que la conductibilité varie, elle, en sens contraire, bien que faiblement. Il y a donc à l'altitude du Jungfraujoch en été le «type continental», alors qu'en automne les conditions se rapprochent du «type océanique». Une analyse plus détaillée montre qu'en été la variation diurne de la «résistance tubulaire» (columnar resistance) au-dessus du Jungfraujoch est en liaison étroite avec la résistance locale de l'air au point de mesure (inverse de la conductibilité), tandis qu'en automne ce n'est plus le cas.Pour interpréter ces résultats il faut admettre ce qui suit: En été la variation diurne de l'échange vertical turbulent modifie les aérosols jusqu'au niveau de la crête alpine, ce que l'on reconnaît au fait que les variations diurnes des phénomènes d'électricité atmosphérique sont largement conditionnés par les couches basses. En automne par contre cet effet a disparu sur les Alpes, car la variation de l'échange turbulent n'a plus d'influence à ce niveau. La variation de la conductibilité qui subsiste suggère un échange d'air par advection. L'allure de la pression de vapeur d'eau au Jungfraujoch en été et en automne confirme cette hypothèse.

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Mit 11 Textabbildungen.     

Zur Entwicklung der luftelektrischen Grundanschauungen

Zusammenfassung Die luftelektrischen Grundanschauungen haben im Laufe der Entwicklung mehrfach erhebliche Wandlungen durchgemacht. Auf die Entwicklungsperiode, in der man die auffallenden Parallelen im Verhalten luftelektrischer und meteorologischer Größen aufzuklären sich bestrebte — sie findet etwa mitF. Exner ihr Ende—, folgt eine Phase bewußter Emanzipation der luftelektrischen Forschung, während der man in den meteorologischen Einflüssen nur Störungen sieht. Etwa in den zwanziger Jahren beginnt dann eine Reaktion gegen dieses Isolationsbestreben und mit der früher lange vergeblich versuchten Aufklärung des luftelektrischen Grund- und Existenzproblems leitet sich eine neue Entwicklungsphase ein, die man sinngemäß als korrelative Phase bezeichnen möchte. Nach einer eingehenden und nach den inneren gründen dieser mehrmaligen Schwenkung suchenden Darstellung wird im zweiten Teil der vorliegenden Arbeit das Problem der luftelektrischen Tagesgänge behandelt und als Beweis für die komplexe elektro-meteorologische Arbeits- und Betrachtungsweise in seinen neuesten Entwicklungen kurz dargestellt. Die enge Verbindung zwischen dem luftelektrischen Geschehen und dem vertikalen atmosphärischen Massenaustausch legt die Benutzung luftelektrischer Untersuchungen in der Austausch-und Luftkörperforschung nahe.

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Summary In the course of the development the fundamental notions about atmospheric electricity have experienced considerable changes. In a first period expiring about withF. Exner, one tried to explain the striking parallels of electrical and meteorological phenomena; then follows a period with a distinct emancipation of atmospheric electricity, where meteorological influences were admitted but as perturbations. In the twenties begins a reaction to this isolationist views and a new evolution starts which might be called correlative phase. The author analyses and explains these repeated changes, and in a second part he discusses the problem of the diurnal variation of atmospheric electricity and shows the complexity of electro-meteorological relations. The close connexion between the phenomena of atmospheric electricity and the turbulent vertical exchange urges to employ investigations of atmospheric electricity for investigations in exchange and air-mass research.

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Résumé En matière d'électricité atmosphérique les points de vue ont souvent varié considérablement. Dans une première période allant jusqu'àF. Exner environ, on a essayé d'expliquer le parallélisme évident entre les phénomènes électriques et météorologiques; puis on a envisagé les premiers pour eux-mêmes, indépendamment des influences météorologiques considérées alors comme des «perturbations». Autour des années 1920, une réaction se dessine contre cette discrimination, et une nouvelle phase commence que l'on pourrait appeler corrélative. Après une analyse approfondie de ces fluctuations de la théorie, l'auteur aborde dans la deuxième partie de son étude le problème des variations diurnes des phénomènes électriques et montre la complexité des relations les unissant à ceux de l'atmosphère ellemême. La liaison étroite entre les phénomènes de l'électricité atmosphérique et les échanges turbulents de masse dans la verticale prouve l'utilité des recherches électriques pour l'étude de cet échange et pour celle des masses d'air de l'atmosphère.

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Mit 14 Textabbildungen.

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Herrn Prof. Dr.H. Benndorf zum 80. Geburtstag gewidmet.     

Climate variability and trends in downscaled high-resolution simulations and projections over Metropolitan France

In order to fulfill the society demand for climate information at the spatial scale allowing impact studies, long-term high-resolution climate simulations are produced, over an area covering metropolitan France. One of the major goals of this article is to investigate whether such simulations appropriately simulate the spatial and temporal variability of the current climate, using two simulation chains. These start from the global IPSL-CM4 climate model, using two regional models (LMDz and MM5) at moderate resolution (15–20 km), followed with a statistical downscaling method in order to reach a target resolution of 8 km. The statistical downscaling technique includes a non-parametric method that corrects the distribution by using high-resolution analyses over France. First the uncorrected simulations are evaluated against a set of high-resolution analyses, with a focus on temperature and precipitation. Uncorrected downscaled temperatures suffer from a cold bias that is present in the global model as well. Precipitations biases have a season- and model-dependent behavior. Dynamical models overestimate rainfall but with different patterns and amplitude, but both have underestimations in the South-Eastern area (Cevennes mountains) in winter. A variance decomposition shows that uncorrected simulations fairly well capture observed variances from inter-annual to high-frequency intra-seasonal time scales. After correction, distributions match with analyses by construction, but it is shown that spatial coherence, persistence properties of warm, cold and dry episodes also match to a certain extent. Another aim of the article is to describe the changes for future climate obtained using these simulations under Scenario A1B. Results are presented on the changes between current and mid-term future (2021–2050) averages and variability over France. Interestingly, even though the same global climate model is used at the boundaries, regional climate change responses from the two models significantly differ.     

Climate and climate change in western canada as simulated by the Canadian regional climate model

Abstract

A þrst climate simulation performed with the novel Canadian Regional Climate Model (CRCM) is presented. The CRCM is based on fully elastic non‐hydrostatic þeld equations, which are solved with an efþcient semi‐implicit semi‐Lagrangian (SISL) marching algorithm, and on the parametrization package of subgrid‐scale physical effects of the second‐generation Canadian Global Climate Model (GCMII). Two 5‐year integrations of the CRCM nested with GCMII simulated data as lateral boundary conditions are made for conditions corresponding to current and doubled CO₂ scenarios. For these simulations the CRCM used a grid size of 45 km on a polar‐stereographic projection, 20 scaled‐height levels and a time step of 15 min; the nesting GCMII has a spectral truncation of T32, 10 hybrid‐pressure levels and a time step of 20 min. These simulations serve to document: (1) the suitability of the SISL numerical scheme for regional climate modelling, (2) the use of GCMII physics at much higher resolution than in the nesting model, (3) the ability of the CRCM to add realistic regional‐scale climate information to global model simulations, and (4) the climate of the CRCM compared to that of GCMII under two greenhouse gases (GHG) scenarios.     

Particulate content of savanna fire emissions

As part of the FOS-DECAFE experiment at Lamto (Ivory Coast) in January 1991, various aerosol samples were collected at ground level near prescribed fires or under local background conditions, to characterize the emissions of particulate matter from the burning of savanna vegetation. This paper deals with total aerosol (TPM) and carbon measurements. Detailed trace element and polycyclic hydrocarbon data are discussed in other papers presented in this issue.Near the fire plumes, the aerosols from biomass burning are primarily of a carbonaceous nature (C%70% of the aerosol mass) and consist predominantly of submicron particles (more than 90% in mass.) They are characterized by their organic nature (black to total carbon ratio Cb/Ct in the range 3–20%) and their high potassium content (K/Cb0.6). These aerosols undergo aging during their first minutes in the atmosphere causing slight alterations in their size distribution and chemical composition. However, they remain enriched in potassium (K/Cb=0.21) and pyrene, a polycyclic aromatic hydrocarbon, such that both of these species may be used as tracers of savanna burning aerosols. We show that during this period of the year, the background atmosphere experiences severe pollution from both terrigenous sources and regional biomass burning (44% of the aerosol). Daynight variations of the background carbon concentrations suggest that fire ignition and spreading occur primarily during the day. Simultaneous TPM and CO₂ real-time measurements point to a temporal and spatial heterogeneity of the burning so that the ratio of the above background concentrations (TPM/CO₂) varies from 2 to 400 g/kg C. Smoldering processes are intense sources of particles but particulate emissions may also be important during the rapidly spreading heading fires in connection with the generation of heavy brown smoke. We propose emission factor values (EF) for aerosols from the savanna biomass burning aerosols: EF (TPM)=11.4±4.6 and 69±25 g/kg C_{dry plant} and EF(Ct)=7.4±3.4 and 56±16 g C/kg C_{dry plant} for flaming and smoldering processes respectively. In these estimates, the range of uncertainty is mostly due to the intra-fire variability. These values are significantly lower than those reported in the literature for the combustion of other types of vegetation. But due to the large amounts of vegetation biomass being burnt in African savannas, the annual flux of particulate carbon into the atmosphere is estimated to be of the order of 8 Tg C, which rivals particulate carbon emissions from anthropogenic activities in temperate regions.     

Investigating the Halogen Chemistry From High-Latitude Nighttime Stratospheric Measurements of OClO and NO2

Two cases of simultaneous nighttime measurements of NO₂ and OClO in the winter polar stratosphere are analyzed in order to test our present knowledge of halogen chemistry in the presence of high amount of NO₂ at low temperature. Comparisons with Lagrangian model calculations using several hypotheses are performed. First simulations, using the admitted constant rates of chemical reaction, strongly underestimate the measured OClO while the NO₂ profiles are correctly reproduced. If uncertainties in actinic fluxes calculations are taken into account, simulation results do not show a significant reduction of the underestimation. A better agreement can be achieved if the formation of unstable isomers of ClONO₂ and of BrONO₂ occurs in the cold conditions of the polar stratosphere. An approximate value of the branching ratios of the channels leading to ClONO₂ and ClOONO, and to BrONO₂ and BrOONO, necessary to reproduce both OClO and NO₂ is given and discussed.