Buchbesprechungen

Ohne Zusammenfassung     

Paleolimnological assessment of human impacts in Lake Blanca, SE Uruguay

Paleolimnological techniques were used to assess human impacts onLake Blanca, a small (0.6 km²), coastal fresh waterbodyin southern Uruguay, which is the drinking water source for 100,000 localresidents. We retrieved a core that extends to about 1100 ¹⁴Cyr BP. ²¹⁰Pb ages, organic mater, CO₃, totalcarbon, nutrients, fossil pigments and diatoms allowed us to establishlimnological conditions before and after cultural impacts. Soil removal(1880–1960) and intensive cattle and sheep grazing (1943–1966) ledto gully formation in the catchment. This watershed erosion resulted inincreased sedimentation rates. The aquatic system appeared to be mesotrophicwith dominance of epibenthic diatoms until 1966, at which timeeutrophication intensified with forestry activities. Increases in nutrients, aswell as blooms of planktonic diatoms, were observed. During the last decade,tourist/urban development as well as high drinking water demand caused areduction in lake area. Subsequent marked increases in rainfall led to furtherphytoplankton blooms and macrophyte proliferation.     

Zur Frage des Einflusses der Land-und Meerverteilung auf die Lage der quasistationären Tröge in einer atmosphärischen Zonalzirkulation

Zusammenfassung Zur Erklärung der Lage der großen quasistationären Tröge wird einem Rechnungsgang vonCharney undEliassen folgend, neben dem Einfluß der Erhebung der Erdoberfläche auch noch derjenige der Wärmeaufnahme und-abgabe herangezogen, der sich noch größer als der erstgenannte erweist. Erst nach seiner Berücksichtigung steht das Resultat in befriedigender Übereinstimmung mit den beobachteten Werten.

---

Summary In order to explain the position of the great quasi-stationary troughs and ensuing a computation ofCharney andEliassen, the author takes into consideration, apart from the influence of the upheavals of the earth's surface, also the supply and loss of heat. The latter influence proves to be more powerful than the first one, and taking it into consideration the result is in satisfactory agreement with the observed values.

---

Résumé Afin d'expliquer la situation des grands creux quasistationnaires sont pris en considération, en suivant une méthode deCharney etEliassen, à part l'influence des élévations de la surface terrestre, celle due à l'apport et la perte de chaleur, qui se révèle encore plus efficace que la première. Seulement en en tenant compte le résultat correspond d'une façon satisfaisante aux conditions observées.

---

Mit 3 Textabbildungen.     

Das mittlere meridionale Temperaturprofil in der Troposphäre als Effekt von vertikalen und horizontalen Austauschvorgängen und Kondensationswärme

Summary A theoretical account is given for the mean meridional temperature profile in the troposphere (up to 11 km) by the aid of the theorem of turbulent heat conduction introducing the vertical and horizontal coefficients of exchange (Austausch) which show a different order of magnitude. It is necessary, however, to take into consideration the heat of condensation, liberated by condensation of the mean yearly precipitation on the earth and thereby supplied to the troposphere in the different latitudes, in order to obtain a theoretical solution capable of completely explaining the mean meridional temperature profile deduced from former observations in the free atmosphere. The mean temperature distribution on ground has been assumed to be known as it is established by the radiation balance of the ground showing the determined and wellknown zonal distribution. Furthermore, some noticeable details resulting from the theory and concerning the vertical structure of temperature in the troposphere and its state of equilibrium are derived. It is made clear how a temperature gradient <1° C/100 m comes about. Thus the mean meridional temperature profile is shown to be a determined state of equilibrium between vertical and horizontal exchange (Austausch) phenomena and processes of condensation taking place in the troposphere. These latter ones being confined to a certain layer of the lower atmosphere are of essential importance for the upper limitation of the troposphere.

---

Résumé On donne une explication théorique du profil méridien moyen de température dans la troposphère (jusqu'à 11 km.) en s'appuyant sur le théorème de la conductibilité turbulente et en introduisant les coefficients d'échange turbulent dont l'ordre de grandeur n'est pas le même dans la verticale et dans l'horizontale. Il faut tenir compte de la chaleur de condensation libérée par les précipitations annuelles moyennes et qui est fournie à la troposphère aux différentes latitudes; alors seulement on arrive à une solution en accord complet avec le profil méridien de température, tel que le fournissent les observations aérologiques. On a considérée comme connue la distribution moyenne de la température au niveau du sol, celle-ci étant déterminée par le bilan radiatif du sol et présentant la répartition zonale bien connue. On expose ensuite thermique verticale de la troposphère et son équilibre, ainsi que l'établissement d'un gradient inférieur à un degré par cent mètres. Le profil méridien moyen de température apparaît alors comme le résultat d'un équilibre entre les processus d'échange turbulent verticaux et horizontaux et des phénomènes de condensation se produisant dans la troposphère. Le fait que ces derniers sont limités à une certaine couche basse de l'atmosphère est une des raisons pour lesquelles la troposphère présente une limite supérieure.

---

---

Mit 4 Textabbildungen.     

A Lee wave cloud climatology for pincher creek,Alberta

Abstract

The annual, monthly and diurnal frequencies and durations of wave clouds are summarized from twelve years of observations at Pincher Creek, Alberta. Wave clouds occur on an average of 141 days annually. There is a distinct winter maximum anda summer minimum of occurrence. Wave clouds occur on 50% or more of the days during October and February, the most active months. Wave clouds persist for longer periods in the cooler half of the year. There appears to be a marked diurnal variation in wave cloudfrequency with maxima in the afternoon, however, this may be due to decreased visibility at sunrise and sunset.     

Numerical simulation of the development of vortices over the Qinghai-Xizang (Tibet) Plateau

Summary Some of the vortices which develop over the Tibetan plateau during summer give rise to severe weather over eastern China. These weather developments can be difficult to forecast, but have been simulated successfully in a recently developed numerical model. It will be shown that different vortices respond differently to topographic effects, to nonlinear processes and to sensible and latent heating in their formation, maintenance, and motion. Elevated terrain appears to enhance the influence of thermodynamic processes, block airflow, and increase frictional dissipation.Sensible heating sometimes collaborates with topography in blocking cold air intrusions and is not only a function of terrain elevation but also of the synoptic situation. Without the input of latent heating, vortices over the eastern part of the Tibetan plateau tend to degenerate.

---

Numerische Simulation von Wirbelbildungen über dem Hochland von Tibet

Zusammenfassung Einige der sich im Sommer über dem Hochland von Tibet entwickelnden Wirbel verursachen Unwetter in Ostchina. Die Vorhersage dieser Entwicklung kann schwierig sein, sie werden aber von einem kürzlich vorgestellten numerischen Modell erfolgreich simuliert. Es wird gezeigt, daß verschiedene Wirbel verschieden auf die Orographie, auf nichtlineare Vorgänge sowie auf fühlbare und latente Wärme in ihrer Entstehung, Erhaltung und Bewegung reagieren. Ein Hochland scheint den Einfluß thermodynamischer Vorgänge zu verstärken, Strömungen zu blockieren und die Reibungsdissipation zu steigern.Die fühlbare Wärme verhindert manchmal gemeinsam mit der Topographie Kaltlufteinbrüche, hängt aber nicht nur von der Hochland-sondern auch von der synoptischen Situation ab. Ohne latente Wärme neigen Wirbel über dem Ostteil des Hochlandes von Tibet zur Degeneration.

---

---

With 22 Figures     

Assessment of hydrological alterations on wandering beetle assemblages (coleoptera: Carabidae and Tenebrionidae) in coastal wetlands of arid Mediterranean systems

Changes in wandering beetle assemblages (Carabidae and Tenebrionidae) of different habitats situated in coastal wetlands of a Mediterranean arid area (Mar Menor, SE Spain) were analysed in 1984, 1992 and 2003 by pitfall trapping. Over two decades, the increase in irrigated lands at watershed scale led to rising water tables in the Mar Menor wetlands, which affected their beetle communities. These hydrological changes caused an increase in the carabid population, particularly in the sites most affected by flooding, where halobionts and halophiles, which were practically absent in 1984 and 1992, had become dominant by 2003. In contrast, tenebrionid assemblages simplified with time and by 2003 were dominated by one or two generalist species.