Geo–ecology and management of sensitive montane landscapes

Montane (alpine) areas are generally of high value for nature conservation. Such environments and the habitats they support are dynamic and often fragile. They are vulnerable to disturbance from a range of human activities and are responsive to climate changes over short and long timescales. Biodiversity and conservation values are closely linked to geological history, geomorphological processes and soils, and it is crucial that management systems are based on understanding these links.
There are many similarities between the Cairngorm Mountains (Scotland), the Giant Mountains (Czech Republic) and Abisko Mountains (Sweden) in terms of geology, geomorphology, ecology, links with biodiversity and high conservation importance. Comparable pressures and management issues involve, to varying degrees, a history of human use and impacts from deforestation, pasturing, grazing, recreation and atmospheric pollution. Landscape change therefore involves a complex interplay between natural and anthropogenic factors. Managing such change requires better understanding of the geo–ecological processes involved and the factors that determine landscape sensitivity. This is illustrated through a simple framework and examples from the three areas. Comparison of landscape sensitivity between similar montane areas, but in different geographic locations and climatic environments, should allow more informed management planning and a precautionary approach in advance of further changes in human activity and from predicted global warming scenarios.     

The influence of sea waves on the wind profile

From wind profile and wave measurements performed during the JONSWAP II experiment, relations between the dimensionless profile slope and the significant wave height are derived. It is shown that the wind profile is distorted by the waves especially in the vicinity of the water surface. The wave influence on the profile seems to be restricted to heights below about three wave heights. Above this level, the dimensionless profile slope is an approximately constant value corresponding to a drag coefficient of about 1.15 × 10^–3.     

Nitric oxide profiles measured in situ during the Globus '85 campaign

Nitric oxide profiles obtained from three flights of chemiluminescent instruments during the Globus '85 campaign held in France in the autumn of 1985 are reported. When the profile obtained in the early morning of 20 September is compared with the flight made the previous afternoon, an average morning to midday NO ratio of 0.7 for the region between 26 and 33 km is obtained. This value is in good agreement with theoretical studies involving the photolysis of N₂O₅ and the establishment of the NO₂–NO equilibrium.     

On the predictability of decadal changes in the North Pacific

 The predictability of decadal changes in the North Pacific is investigated with an ocean general circulation model forced by simplified and realistic atmospheric conditions. First, the model is forced by a spatially fixed wind stress anomaly pattern characteristic for decadal North Pacific climate variations. The time evolution of the wind stress anomaly is chosen to be sinusoidal, with a period of 20 years. In this experiment different physical processes are found to be important for the decadal variations: baroclinic Rossby waves dominate the response. They move westward and lead to an adjustment of the subtropical and subpolar gyre circulations in such a way that anomalous temperatures in the central North Pacific develop as a delayed response to the preceding wind stress anomalies. This delayed response provides not only a negative feedback but also bears the potential for long-term predictions of upper ocean temperature changes in the central North Pacific. It is shown by additional experiments that once these Rossby waves have been excited, decadal changes of the upper ocean temperatures in the central North Pacific evolve without any further anomalous atmospheric forcing. In the second part, the model is forced by surface heat flux and wind stress observations for the period 1949–1993. It is shown that the same physical processes which were found to be important in the simplified experiments also govern the evolution of the upper ocean in this more realistic simulation. The 1976/77 cooling can be mainly attributed to anomalously strong horizontal advection due to the delayed response to persistent wind stress curl anomalies in the early 1970s rather than local anomalous atmospheric forcing. This decadal change could have been predicted some years in advance. The subsequent warming in the late 1980s, however, cannot be mainly explained by advection. In this case, local anomalous atmospheric forcing needs to be considered. Received: 6 July 1998 / Accepted: 16 October 1999     

Estimation of Sensible Heat Flux from Surface Temperature Wave and One-Time-of-Day Air Temperature Observation

By means of the algorithm presented here, the temporal course H(t) and the daily mean H¯ of the sensible heat flux H can be estimated from measurements of the thermodynamic surface temperature (as a function of time) and from a one-time-of-day air temperature observation. In addition to these temperatures, one needs estimates for daily mean wind speed, for the roughness lengths of momentum and heat transfer, and for the displacement height. First, a quite general solution of the equation for heat conductance (equation for the vertical profile of potential temperature (z,t)) in the dynamic sublayer will be presented. The undetermined parameters in this solution will be defined with the aid of the above mentioned measurements. The influence of horizontal advection will be taken into account. After that, the sensible heat flux can be evaluated from the temperature difference between surface and air with the well known resistance formulae. In this paper the algorithm is derived for areas with homogeneous surfaces, i.e., with uniform surface temperatures. Finally, the method will be verified by measurements taken during the field campaigns HIBE 89 (Hildesheimer Börde in Germany) and EFEDA 91 (Spain). The root mean square errors (RMSE) for the comparison between measurement and model with regard to the temperature difference of surface and air amount to one or two degrees Kelvin, and the error of H¯ reaches 10 to 25 per cent. The method can be used to determine the sensible heat flux from measurements of surface temperatures by satellites (e.g., METEOSAT), but can also be applied to ground based measurements. For instance, horizontal temperature advection can be estimated from measurements at a single location, especially if more than one near-surface air temperature is available. The procedure can be generalized for larger areas, which consist of various surface types with different surface temperatures. This generalization of the algorithm is in progress and will be addressed in a subsequent paper. It will allow us to improve the estimates for H(t) by means of temperature measurements from, e.g., NOAA/AVHRR or LANDSAT/TM, taking into account the heterogeneity of the area that is contained in one METEOSAT pixel.     

A Three-Dimensional Global Model Study of Carbonyl Sulfide in the Troposphere and the Lower Stratosphere

Global distributions of carbonyl sulfide and carbon disulfide have been calculated with a three-dimensional global model of the atmospheric general circulation (ECHAM). The model calculates a global sink strength for carbonyl sulfide of 0.3 Tg S yr^-1, with vegetation uptake being the largest sink. With this sink strength, the sources have to be close to the lower limit of the present estimate in the literature. The calculated mixing ratios are higher in the Southern Hemisphere than in the Northern Hemisphere. This interhemispheric gradient is the opposite of what is observed demonstrating that the present knowledge of the distribution of sinks and sources is not fully adequate. The model calculations support the idea that the open oceans could act as a net sink of carbonyl sulfide. The calculated stratospheric photolysis of carbonyl sulfide constitutes about 4% of the total sink of carbonyl sulfide. A stratospheric production of sulfate from carbonyl sulfide of 0.013 Tg S yr^-1 is obtained, which is 3 to 12 times less than what is needed to maintain the stratospheric sulfate aerosol layer. Although these results are associated with uncertainties, due to the low upper boundary and coarse vertical resolution of the model, they support recent findings of a low stratospheric production of sulfate from carbonyl sulfide. Instead, sulfur dioxide transported from the troposphere is calculated to be the most important precursor for the stratospheric sulfate aerosol layer.     

Der Einfluß der Temepratur auf das atmosphärische Ozon

Zusammenfassung A. undE. Vassy haben 1941 versucht, den atmosphärischen Ozongehalt (Gesamtozon) aus den entsprechenden Variationen der Stratosphärentemperatur und der eingestrahlten Sonnenenergie vollständig zu erklären. Sie machten zu diesem Zweck den Ansatze/J=f (T), und zeigten, daß die auf diesem Weg empirisch gefundene Funktionf (T) näherungsweise mit der Temperaturabhängigkeit der für das Ozongleichgewicht wesentlichen Reaktionskonstantenk (T) übereinstimmt. Im Gegensatz dazu kamen andere Autoren (Schröer, Dütsch undCraig), die unabhängig voneinander die photochemische Ozontheorie weiter ausbauten, zum Schluß, daß die gemessenen atmosphärischen Ozonbeträge keine rein photochemischen Gleichgewichtswerte sein können.Zur Aufklärung dieser Differenz wird der von A. undE. Vassy aufgestellte und als erste Näherung bezeichnete Ansatz hier auf Grund der photochemischen Theorie, die noch einmal knapp entwickelt wird, untersucht, wobei vor allem folgende Mängel festgestellt werden: Der Ansatz von A. undE. Vassy bringt eine enorme Überschätzung des Temperatureinflusses auf das Gesamtozon mit sich, was anhand von zwei, nach der photochemischen Theorie durchgerechneten Zahlenbeispielen belegt wird; wegen der Hereinahme der Tageslänge in den Ansatz zur Berechnung vonJ, welches Vorgehen der photochemischen Auffassung widerspricht, wird auch der Einfluß des wechselnden Sonnenstandes falsch eingeschätzt. Auf Grund der hier durchgeführten Untersuchung muß daher die von A. undE. Vassy aufgestellte Hypothese abgelehnt werden.

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Summary In 1941 A. andE. Vassy made an attempt to explain the atmospheric ozone content (total amount of ozone) fully from the corresponding variations of the temperature of the stratosphere and the total incoming solar energy. They started from the equatione/J=f (T) and showed that this empirically established functionf (T) depends on temperature approximately in the same manner as the reaction constantk (T) which is essential for the ozone equilibrium. In opposition to themSchröer, Dütsch andCraig enlarging the photochemical theory of ozone independent of each other infered that the measured total amounts of ozone cannot be explained by purely photochemical equilibrium conditions.An attempt is made here to clear up this difference by examining the formula, put forward by A. andE. Vassy as a first approximation. It is made along the lines of the photochemical theory, which is briefly explained. In this connection some shortcomings of theVassy theory are stated: The formula of A. andE. Vassy comprises a considerable overestimation of the influence of temperature exerted on the total amount of ozone, which criticism is supported by two numerical instances computed according to the photochemical theory. Owing to the fact that the length of the day is also considered in the formula for the calculation ofJ, which proceeding is in plain contradiction to the photochemical conception, the influence of the changing solar position is estimated erroneously as well. On the basis of the examination carried out here the hypothesis set out by A. andE. Vassy must be refused.

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Résumé A. etE. Vassy ont essayé en 1941 d'expliquer la teneur en ozone de l'atmosphère à l'aide des variations correspondantes de la température de la stratosphère et de l'énergie solaire rayonnée. Ils ont à cet effet posé que:e/J=f (T), et ils ont prétendu que la fonctionf (T) trouvée ainsi empiriquement correspond à peu près à celle qui lie la constante de réactionk (T) pour l'équilibre de l'ozone avec la températureT. Par contre trois auteurs (Schröer, Dütsch etCraig) qui indépendamment l'un de l'autre ont élaboré la théorie photochimique de l'ozone ont conclu que les teneurs observées ne peuvent correspondre à un équilibre photochimique pur.Pour expliquer ces divergences, on examine ici l'hypothèse de E. etA. Vassy dans le cadre de la théorie photochimique brièvement rappelée. On constate que cette hypothèse conduit à surestimer fortement le rôle de la température dans la quantité totale de l'ozone, fait confirmé par deux exemples numériques fondés sur la théorie photochimique; en introduisant la longueur du jour dans le calcul deJ — ce qui est contraire au point de vue photochimique — on tient faussement compte de l'effet de la variation de la hauteur solaire. La conclusion de cette étude est que l'hypothèse de E. etA. Vassy doit être rejetée.

     

Buchbesprechungen

Ohne Zusammenfassung     

Beiträge zu einer elektrischen Tornadotheorie

Zusammenfassung Ein VorschlagB. Vonneguts, elektrische Tornadotheorien wieder in Betracht zu ziehen, wird aufgegriffen und es wird gezeigt, daß die Gewittertheorie mit der elektromagnetischen Induktion als Grundlage auch auf das Tornadoproblem anwendbar ist. Dadurch finden nicht nur mehrere Eigenschaften des Tornados eine zwanglose Erklärung, vielmehr wird darüber hinaus auch die Wahrscheinlichkeit der Brauchbarkeit der Gewittertheorie bedeutend erhöht. Das beste Argument für die Wirksamkeit der elektromagnetischen Induktion dürfte in der Beobachtung einer rhombusförmigen, mehrere Tornados erzeugenden Gewitterwolke zu sehen sein, die durch das Raumgitter einer Dipolwolke befriedigend erklärt werden kann.Summary Following a suggestion byB. Vonnegut to reconsider electrical torando theories, the author shows that the thunderstorm theory based on electromagnetic induction is also applicable to the tornado problem. Several characteristics of the tornado are easily explained, adding evidence of the validity of the thunderstorm theory. The strongest argument in favour of the effectiveness of electromagnetic induction may be considered the observation of a rhomb-shaped thunderstorm cloud which generated several tornadoes. Such a cloud can be explained by the spacial distribution of its dipole elements.

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Résumé L'auteur se réfère à la proposition deB. Vonnegut de reconsidérer la théorie électrique des tornades. Il démontre que la théorie des orages, basée sur l'induction électro-magnétique, est également applicable au problème des tornades. Non seulement on explique aisément par ce moyen plusieurs propriétés des tornades, mais encore la probabilité de la valeur d'application de la théorie des orages en est sensiblement renforcée. Le meilleur argument en faveur de l'activité de l'induction électro-magnétique est certes l'observation d'un nuage d'orage en losange qui engendra plusieurs tornades. Cette formation peut s'expliquer de façon satisfaisante par la grille spaciale d'un nuage en dipole.

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Mit 6 Textabbildungen

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Dem Gedenken an Priv.-Doz. Dr.Fritz Rossmann gewidmet.