University of Potsdam

About: University of Potsdam is a education organization based out in Potsdam, Germany. It is known for research contribution in the topics: Population & Computer science. The organization has 9629 authors who have published 26740 publications receiving 759745 citations. The organization is also known as: Universität Potsdam.

BEEHAVE: a systems model of honeybee colony dynamics and foraging to explore multifactorial causes of colony failure

Abstract: A notable increase in failure of managed European honeybee Apis mellifera L. colonies has been reported in various regions in recent years. Although the underlying causes remain unclear, it is likely that a combination of stressors act together, particularly varroa mites and other pathogens, forage availability and potentially pesticides. It is experimentally challenging to address causality at the colony scale when multiple factors interact. In silico experiments offer a fast and cost-effective way to begin to address these challenges and inform experiments. However, none of the published bee models combine colony dynamics with foraging patterns and varroa dynamics.We have developed a honeybee model, BEEHAVE, which integrates colony dynamics, population dynamics of the varroa mite, epidemiology of varroa-transmitted viruses and allows foragers in an agent-based foraging model to collect food from a representation of a spatially explicit landscape.We describe the model, which is freely available online (www.beehave-model.net). Extensive sensitivity analyses and tests illustrate the model's robustness and realism. Simulation experiments with various combinations of stressors demonstrate, in simplified landscape settings, the model's potential: predicting colony dynamics and potential losses with and without varroa mites under different foraging conditions and under pesticide application. We also show how mitigation measures can be tested.Synthesis and applications. BEEHAVE offers a valuable tool for researchers to design and focus field experiments, for regulators to explore the relative importance of stressors to devise management and policy advice and for beekeepers to understand and predict varroa dynamics and effects of management interventions. We expect that scientists and stakeholders will find a variety of applications for BEEHAVE, stimulating further model development and the possible inclusion of other stressors of potential importance to honeybee colony dynamics.

Optical and microphysical characterization of biomass-burning and industrial-pollution aerosols from multiwavelength lidar and aircraft measurements.

Abstract: [1] During the Lindenberg Aerosol Characterization Experiment (LACE 98) simultaneous measurements with ground-based and airborne lidars and with two aircraft equipped with aerosol in situ instrumentation were performed. From the lidar measurements, particle backscatter coefficients at up to eight wavelengths between 320 and 1064 nm and particle extinction coefficients at 2–3 wavelengths between 292 and 532 nm were determined. Thus, for the first time, an extensive set of optical particle properties from several lidar platforms was available for the inversion into particle microphysical quantities. For this purpose, two different inversion algorithms were used, which provide particle effective radius, volume, surface-area, and number concentrations, and complex refractive index. The single-scattering albedo follows from Mie-scattering calculations. The parameters were compared to the ones from airborne measurements of particle size distributions and absorption coefficients. Two measurement cases were selected. During the night of 9–10 August 1998 measurements were taken in a biomass-burning aerosol layer in the free troposphere, which was characterized by a particle optical depth of about 0.1 at 550 nm. Excellent agreement between remote-sensing and in situ measurements was found. In the center of this plume the effective radius was approximately 0.25 μm, and all methods showed rather high complex refractive indices, ranging from 1.56–1.66 in real part and from 0.05–0.07i in imaginary part. The single-scattering albedo showed low values from 0.78–0.83 at 532 nm. The second case, taken on 11 August 1998, presents the typical conditions of a polluted boundary layer in central Europe. Optical depth was 0.35 at 550 nm, and particle effective radii were 0.1–0.2 μm. In contrast to the first case, imaginary parts of the refractive index were below 0.03i. Accordingly, the single-scattering albedo ranged from 0.87–0.95.

The Convective and Orographically-induced Precipitation Study (COPS): the scientific strategy, the field phase, and research highlights

Abstract: Within the framework of the international field campaign COPS (Convective and Orographically induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. This includes networks of in situ and remote-sensing systems such as the Global Positioning System as well as a synergy of multi-wavelength passive and active remote-sensing instruments such as advanced radar and lidar systems. The COPS field phase was performed from 01 June to 31 August 2007 in a low-mountain area in southwestern Germany/eastern France covering the Vosges mountains, the Rhine valley and the Black Forest mountains. The collected dataset covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase until their decay. Eighteen Intensive Observations Periods with 37 operation days and eight additional Special Observations Periods were performed, providing a comprehensive dataset covering different forcing conditions. In this article, an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS research provides new insight into key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of quantitative precipitation forecasting by the assimilation of new observations, and in the performance of ensembles of convection-permitting models in complex terrain.

How to avoid potential pitfalls in recurrence plot based data analysis

Abstract: Recurrence plots and recurrence quantification analysis have become popular in the last two decades. Recurrence based methods have on the one hand a deep foundation in the theory of dynamical systems and are on the other hand powerful tools for the investigation of a variety of problems. The increasing interest encompasses the growing risk of misuse and uncritical application of these methods. Therefore, we point out potential problems and pitfalls related to different aspects of the application of recurrence plots and recurrence quantification analysis.