Ildikó Pieczka

Analysis of regional climate change modelling experiments for the Carpathian Basin

In the last decade, Regional Climate Models (RCMs) nested in Global Climate Models (GCMs) have become essential tools to make climate projections with fine spatial resolution. In this paper, control runs of the RCMs RegCM and PRECIS are discussed and compared for the Central/Eastern European region. Both RCMs are three-dimensional, sigma-coordinate, primitive equation models, for the control experiments (1961-1990), they use initial and lateral boundary conditions from the European Centre for Medium-range Weather Forecast (ECMWF) reanalysis data sets (ERA-40). For the validation, monthly data sets of the Climatic Research Unit (CRU) of the University of East Anglia are used. According to the results, the model RegCM generally underestimates the temperature, while the model PRECIS overestimates it. The precipitation is generally overestimated by the RegCM simulations, and underestimated by the PRECIS simulations. In the case of PRECIS, a model experiment for the Central/Eastern European region for the 2071-2100 period is completed using the HadCM3 GCM outputs (A2 scenario) as boundary conditions. The results suggest that the significant temperature increase expected in the Carpathian Basin may considerably exceed the global warming rate. The climate of this region is expected to become wetter in winter and drier in the other seasons.

Advanced Numerical Methods for Complex Environmental Models: Needs and Availability

The understanding of lakes physical dynamics is crucial to provide scientifically credible information foron lakes ecosystem management. We show how the combination of in-situ dataobservations, remote sensing observationsdata and three15 dimensional hydrodynamic (3D) numerical simulations is capable of deliveringresolving various spatio-temporal scales involved in lakes dynamics. This combination is achieved through data assimilation (DA) and uncertainty quantification. In this study, we presentdevelop a flexible framework forby incorporating DA into lakes three-dimensional3D hydrodynamic lake models. Using an Ensemble Kalman Filter, our approach accounts for model and observational uncertainties. We demonstrate the framework by assimilating in-situ and satellite remote sensing temperature data into a three-dimensional3Dl hydrodynamic 20 model of Lake Geneva. Results show that DA effectively improves model performance over a broad range of spatio-temporal scales and physical processes. Overall, temperature errors have been reduced by 54 %. With a localization scheme, an ensemble size of 20 members is found to be sufficient to derive covariance matrices leading to satisfactory results. The entire framework has been developed for the constraintswith a goal of near real-time operational systems and near real-time operations (e.g. integration into meteolakes.ch). 25

Dynamical Downscaling of Projected 21st Century Climate for the Carpathian Basin

According to the Working Group I contributions (Solomon et al., 2007) to the Fourth Assessment Report of the Intergovermental Panel on Climate Change (IPCC), the key processes influencing the European climate include increased meridional transport of water vapour, modified atmospheric circulation, reduced winter snow cover (especially, in the northeastern regions), more frequent and more intense dry conditions of soil in summer in the Mediterranean and central European regions. Future projections of IPCC for Europe suggest that the annual mean temperature increase will likely to exceed the global warming rate in the 21st century. The largest increase is expected in winter in northern Europe (Benestad, 2005), and in summer in the Mediterranean area. Minimum temperatures in winter are very likely to increase more than the mean winter temperature in northern Europe (Hanssen-Bauer et al., 2005), while maximum temperatures in summer are likely to increase more than the mean summer temperature in southern and central Europe (Tebaldi et al., 2006). Concerning precipitation, the annual sum is very likely to increase in northern Europe (Hanssen-Bauer et al., 2005) and decrease in the Mediterranean area. On the other hand, in central Europe, which is located at the boundary of these large regions, precipitation is likely to increase in winter, while decrease in summer. In case of the summer drought events, the risk is likely to increase in central Europe and in the Mediterranean area due to projected decrease of summer precipitation and increase of spring evaporation (Pal et al., 2004; Christensen & Christensen, 2004). As a consequence of the European warming, the length of the snow season and the accumulated snow depth are very likely to decrease over the entire continent (Solomon et al., 2007). Coarse spatial resolution of global climate models (GCMs) is inappropriate to describe regional climate processes; therefore, GCM outputs of typically 100-300 km may be misleading to compose regional climate change scenarios for the 21st century (Mearns et al., 2001). In order to determine better estimations of regional climate conditions, fine resolution regional climate models (RCMs) are widely used. RCMs are limited area models nested in GCMs, i.e., the initial and the boundary conditions of RCMs are provided by the GCM outputs (Giorgi, 1990). Due to computational constrains the domain of an RCM evidently does not cover the entire globe, and sometimes not even a continent. On the other hand, their horizontal resolution may be as fine as 5-10 km. In Europe, the very first comprehensive and coordinated effort for providing RCM projections was the project PRUDENCE (Prediction of Regional scenarios and Uncertainties

Climate change scenarios for hungary based on numerical simulations with a dynamical climate model

Climate models are systems of partial differential equations based on the basic laws of physics, fluid motion, and chemistry The use of high resolution model results are essential for the generation of national climate change scenarios Therefore we have adapted the model PRECIS (Providing REgional Climates for Impacts Studies), which is a hydrostatic regional climate model HadRM3P developed at the UK Met Office, Hadley Centre, and nested in HadCM3 GCM It uses 25 km horizontal resolution transposed to the Equator and 19 vertical levels with sigma coordinates. First, the validation of the model (with two different sets of boundary conditions for 1961–1990) is accomplished Results of the different model experiments are compared to the monthly climatological data sets of the Climatic Research Unit (CRU) of the University of East Anglia as a reference Significance of the seasonal bias fields is checked using Welchs t-test Expected future changes — in mean values, distributions and extreme indices — are analysed for the period 2071–2100 The results suggest that the significant temperature increase expected in the Carpathian Basin may considerably exceed the global warming rate The climate of this region is expected to become wetter in winter and drier in the other seasons.

Sensitivity analysis of different parameterization schemes using RegCM4.3 for the Carpathian region

In order to quantify the impact of the use of different parameterization schemes on regional climate model outputs, hindcast experiments have been completed applying the Regional Climate Model version 4.3 (RegCM4.3) for the Carpathian region and its surroundings at 10-km horizontal resolution with three different cumulus convection schemes. Besides, the sensitivity of outputs for subgrid-scale processes is also studied by activating the subgrid Biosphere-Atmosphere Transfer Scheme (BATS) model within other RegCM experiments. Among the analyzed factors, RegCM is most sensitive to the applied convection scheme. The impact of closure assumption related to the used convective parameterization is secondary, while the use of subgridding has less influence on the outputs. RegCM4.3 results show improved performance over our previous model simulations but still have larger amplitude for annual precipitation cycle than the measurement-based reference data. Our validation results for temperature and precipitation suggest that for the selected region, the overall best performance is achieved when using the mixed Grell-Emanuel scheme together with Fritsch and Chappell closure.

Expected trends of regional climate change for the Carpathian Basin for the 21st century

The Regional Climate Models (RCMs) nested into Global Climate Models (GCMs) are expected to improve the regional climate change scenarios for the European subregions. This paper discusses the RCM experiments for the end of the 21st century using the model Providing REgional Climates for Impact Studies (PRECIS) for the Carpathian Basin. Expected future changes in mean values, distributions and empirical probabilities are analysed for the period 2071–2100 (compared to 1961–1990, as a reference period). Significant warming and annual drying is projected, together with substantial changes in the distribution of daily mean temperature and monthly mean precipitation.

Computational Analysis of Expected Climate Change in the Carpathian Basin Using a Dynamical Climate Model

For analyzing the possible regional climate change in the Carpathian Basin, model PRECIS has been adapted, which is the hydrostatic regional climate model HadRM3P developed at the UK Met Office, Hadley Centre, and nested in HadCM3 GCM. First, control run simulations (1961-1990) of the PRECIS model (with two different sets of boundary conditions) are analyzed. In the validation, seasonal temperature and precipitation mean values from the CRU datasets are used. According to the results, model PRECIS slightly overestimates the temperature and underestimates the precipitation. Then, model results for the periods 2071-2100 (using SRES A2 scenario) and 1961-1990 (as the reference period) are compared. The results suggest that the temperature increase expected in the Carpathian Basin may considerably exceed the global warming rate. The climate of this region is expected to become wetter in winter and drier in the other seasons.