Marieke A. Frassl

Use of a weather generator for simulating climate change effects on ecosystems

We present a new vector-autoregressive weather generator developed to generate meteorological time series for climate impact studies on ecosystems.As an example, the weather generator was applied in combination with a hydrodynamic-ecological lake model (DYRESM-CAEDYM). The effects of a warmer and more variable climate on hydrodynamics and phytoplankton in large monomictic lakes were analysed.The weather generator reproduced dependency structures of measured meteorological data. Variability was altered at a time scale similar to lengths of synoptic disturbances, resulting in longer than day-to-day fluctuation changes.Sensitivity of spring bloom development towards a warmer climate, increased climate variability and a combination of both was addressed. For this purpose, 500 meteorological time series per scenario were generated as input for the lake model. We found that onset and maximum of phytoplankton spring bloom are sensitive towards spring weather conditions and that an increase in variability favours early as well as late blooms. Display Omitted We developed a weather generator for scenarios with changed mean and/or variability.The scenarios were used as input for a coupled hydrodynamic-ecological lake model.The effect on stratification and plankton phenology was examined.Increase in mean temperature shifts distribution of blooming dates.Increase in variability favours earlier as well as later blooms.

Virtual geographic environments for water pollution control

ABSTRACT Due to extensive water pollution in Chinese rivers and lakes, large efforts have to be made to improve the quality of drinking water and manage the sewage water treatment process. We propose a general workflow for integrating a large number of heterogeneous data sets relating to various hydrological compartments into a Virtual Geographic Environment (VGE). This allows both researchers and stakeholders to easily access complex data collections in a unified context, find interrelations or inconsistencies between data sets and evaluate simulation results with respect to other observations or simulations in the same region. A prototype of such a VGE has been set up for the region around Chao Lake, containing more than 20 spatial data sets and collections as well as first simulation result. The prototype has been successfully presented to researchers and stakeholders from China and Germany.