Analysis of Climate Model Outputs Using Linear and Nonlinear Statistical Techniques

Regional climate models (RCMs) are currently one of regularly applied tools for localization of global climate models (GCMs) outcomes. This study is focused on analyses of mean daily temperature and precipitation using linear and nonlinear statistical techniques. 48 grid points of the regional climate models HIRHAM and RCAO and 29 meteorological stations of the Czech Republic were compared in the period 1961-1990. Mean annual courses of mean daily temperature and precipitation in the period 20712100 were analyzed at selected HIRHAM and RCAO grid points for A2 and B2 emission scenarios [IPCC, 2007]. Furthermore, time-delayed average mutual information (AMI) and autocorrelation function were analyzed. AMI and autocorrelation function were calculated for one selected time series of each grid point of the Czech Republic and Europe with a time lag varying from 1 to 10 days. The values of average mutual information were compared with values of autocorrelation function. Introduction Climate models have four types of uncertainties [Räisännen, 2007] – initial conditions, boundary conditions, parametrization of the processes, the scale of which is smaller than model resolution, and model design (used mathematical equations and numerical methods of their solutions). Lots of studies are focused on these uncertainties and study reliability of the models on the basis of three criteria: 1. ability of the model to simulate recent climate using comparison of model and real data, 2. conformity of different models by simulation of climate change in the future and 3. ability of the model to simulate climate changes in the past [Räisännen, 2007]. Bloh et al. [2005] compared outputs of climate models with Climate Research Unit data. Tebaldi and Knutti [2007] tried to compensate uncertainties using multi-model ensembles; many other studies were focused on this problem: Giorgi and Mearns [2002], Forest et al. [2000, 2001, 2002], Webster et al. [2003], Santer et al. [1990], Maining and Petit [2005]. Data and methods Six model runs of regional models RCAO and HIRHAM were obtained from PRUDENCE project (http://prudence.dmi.dk/data) in netCDF format. NetCDF format is currently used for systematic archivation of climate model’s results. I focused on grid points in the Czech Republic and in surrounding areas. The reference period was 1961-1990, experiments were analyzed for two IPCC emission scenarios A2 and B2 [IPCC, 2007] in the period 2071-2100. Mean daily air temperature in two meters above ground and mean daily precipitation were analyzed for each model run. The model Figure 1. Location of the grid points of models HIRHAM (left) and RCAO (right). 235 WDS'09 Proceedings of Contributed Papers, Part III, 235–240, 2009. ISBN 978-80-7378-103-3 © MATFYZPRESS