Modeled differences in predicted effects are increasingly used to help quantify the uncertainty of these effects. Here, we examine modeled differences in the aerosol indirect effect in a series of experiments that help to quantify how and why model-predicted aerosol indirect forcing varies between models. The experiments start with an experiment in which aerosol concentrations, the parameterization of droplet concentrations and the autoconversion scheme are all specified and end with an experiment that examines the predicted aerosol indirect forcing when only aerosol sources are specified. Although there are large differences in the predicted liquid water path among the models, the predicted aerosol first indirect effect for the first experiment is rather similar, about −0.6Wm−2 to −0.7Wm−2. Changes to the autoconversion scheme can lead to large changes in the liquid water path of the models and to the response of the liquid water path to changes in aerosols. Adding an autoconversion scheme that depends on the droplet concentration caused a larger (negative) change in net outgoing shortwave radiation compared to the 1st indirect effect, and the increase varied from only 22% to more than a factor of three. The change in net shortwave forcing in the models due to varying the autoconversion scheme depends on the liquid water content of the clouds as well as their predicted droplet concentrations, and both increases and decreases in the net shortwave forcing can occur when autoconversion schemes are changed. The parameterization of cloud fraction within models is not sensitive to the aerosol concentration, and, therefore, the response of the modeled cloud fraction within the present models appears to be smaller than that which would be associated with model “noise”. The prediction of aerosol concentrations, given a fixed set of sources, leads to some of the largest differences in the predicted aerosol indirect radiative forcing among the models, with values of cloud forcing ranging from −0.3Wm−2 to −1.4Wm−2. Thus, this aspect of modeling requires significant improvement in order to improve the prediction of aerosol indirect effects.

Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (tau a) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. cloud droplet number concentration (N d) compares relatively well to the satellite data at least over the ocean. The relationship between (tau a) and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and tau a as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld–tau a relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between tau a and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - tau a relationship show a strong positive correlation between tau a and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of tau a, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clearand cloudy-sky forcings with estimates of anthropogenic tau a and satellite-retrieved Nd–tau a regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5Wm−2, with a total estimate of −1.2±0.4Wm−2.

Der Anbau von schnellwachsenden Baumarten im Kurzumtrieb auf landwirtschaftlichen Flächen ist eine spezielle Produktionsrichtung in der landwirtschaftlichen Pflanzenproduktion. Im zwei- bis zwanzigjährigen Umtrieb werden Schwachholzsortimente erzeugt, die als Brennstoff oder Industrieholz verwendet werden können. Diese Form des Anbaus unterscheidet sich von der forstlichen Nutzung durch wesentlich höhere Stammzahlen pro Hektar, geringere Stammdurchmesser und Stammeinzelgewichte. In der Fachbroschüre wird ein Überblick von der Pflanzung über Pflege- und Schutzmaßnahmen, die Umweltwirkung bis zur Ernte von schnellwachsenden Baumarten auf Kurzumtriebsplantagen gegeben. Gleichzeitig wird über Fragen der stofflichen und energetischen Verwertung als nachwachsender Rohstoff sowie der Wirtschaftlichkeit informiert.

Um statistische Zusammenhänge zwischen Lufttemperatur und Wassertemperatur zu analysieren, wurden zunächst in einer Vorstudie alle kurzfristig verfügbaren Temperaturmessungen in Oberflächengewässern sowie im Boden-, Sicker- und Grundwasser gesammelt, fehlerbereinigt und in Datenbanken zusammengeführt. Die erzeugten 600.000 Datensätze können direkt mit Daten zu Lufttemperatur, Sonnenscheindauer oder globaler Strahlung aus naheliegenden Wetterstationen verknüpft und somit für künftige Auswertungen genutzt werden. Die Prüfung unterschiedlicher Wassertemperaturmodelle hat gezeigt, dass sich für eine sachsenweite Analyse zur Abschätzung der Auswirkung des Klimawandels auf Wassertemperaturen die einfacheren statistischen Methoden aufgrund ihrer Datenverfügbarkeit eher eignen als die fachlich genauer erscheinenden komplexen Modelle mit Berechnungen zu Energiehaushalt und Wärmeaustausch von Gewässern. In Heft 40/2011 der Schriftenreihe werden die Zusammenhänge der klimawandelbedingten Lufttemperaturänderungen auf die Wassertemperaturen analysiert und detailliert dargestellt.

Zugl.: Mainz, Univ., Diss.

Universiẗat-Gesamthochsch., Diss.--Paderborn, 1997.

University, Diss., 2004--Bremen. / Enth. 3 Sonderabdr. aus verschiedenen Zeitschr.

Techn. University, Diss., 2005--München.

Universiẗat, Diss., 2004--Würzburg. / Erscheinungsjahr an der Haupttitelstelle: 2003.

Thesis (doctoral)--Christian-Albrechts-Universität zu Kiel, 1999.