Spectral diagonal ensemble Kalman filters

A new type of ensemble Kalman filter is developed, which is based on replacing the sample covariance in the analysis step by its diagonal in a spectral basis. It is proved that this technique improves the aproximation of the covariance when the covariance itself is diagonal in the spectral basis, as is the case, e.g., for a second-order stationary random field and the Fourier basis. The method is extended by wavelets to the case when the state variables are random fields, which are not spatially homogeneous. Efficient implementations by the fast Fourier transform (FFT) and discrete wavelet transform (DWT) are presented for several types of observations, including high-dimensional data given on a part of the domain, such as radar and satellite images. Computational experiments confirm that the method performs well on the Lorenz 96 problem and the shallow water equations with very small ensembles and over multiple analysis cycles.Comment: 15 pages, 4 figure

INTERNET ADDICTION: A REVIEW OF THE FIRST TWENTY YEARS

Easy access to communication and information technologies has increased our dependence on technology for various aspects of our lives. Nevertheless, this remarkable growth of Internet Usage has been inextricably paired with a rise of excessive and dysfunctional Internet use. Conceptualized around 1996, a few years after the inception of the World Wide Web, Internet addiction has developed into a global issue influencing varying segments of the population at different levels. Despite heated debates on its addictive nature, consensus is emerging regarding the existence of this problematic behavior. In this paper we provide a comprehensive overview of the literature on Internet addiction in last 20 years. Purpose of this paper is to present crucial findings on Internet addiction to health profession. Besides numerous benefits of Internet use, the virtual environment brings various risks in every age group. The Internet is very significant in the everyday activities of children and youth and professional interventions with this age group should be specific considering their developmental characteristics. Exposure to online risks can have long-lasting and intense negative effects. Effective programs in prevention and treatment should include a multi-sectoral and interdisciplinary approach. Detail review of the symptomatology, diagnosis model an possibilities of treatment can be multiple beneficial to the health professionals and other helping professions due to actual needs for interventions in the field of the internet addiction treatment. Internet addiction is slowly becoming a societal concern as it particularly affects adolescents and children, who are more exposed and consequently more vulnerable. Findings presented in the paper can benefit in practice of treatment internet addiction and also as framework for further researches in the field

Data Assimilation of Satellite Fire Detection in Coupled Atmosphere-Fire Simulation by WRF-SFIRE

Currently available satellite active fire detection products from the VIIRS and MODIS instruments on polar-orbiting satellites produce detection squares in arbitrary locations. There is no global fire/no fire map, no detection under cloud cover, false negatives are common, and the detection squares are much coarser than the resolution of a fire behavior model. Consequently, current active fire satellite detection products should be used to improve fire modeling in a statistical sense only, rather than as a direct input. We describe a new data assimilation method for active fire detection, based on a modification of the fire arrival time to simultaneously minimize the difference from the forecast fire arrival time and maximize the likelihood of the fire detection data. This method is inspired by contour detection methods used in computer vision, and it can be cast as a Bayesian inverse problem technique, or a generalized Tikhonov regularization. After the new fire arrival time on the whole simulation domain is found, the model can be re-run from a time in the past using the new fire arrival time to generate the heat fluxes and to spin up the atmospheric model until the satellite overpass time, when the coupled simulation continues from the modified state.Comment: 9 pages, VII International Conference on Forest Fire Research, Coimbra, Portugal, November 17-20, 201

Identifying causal gateways and mediators in complex spatio-temporal systems

J.R. received support by the German National Academic Foundation (Studienstiftung), a Humboldt University Postdoctoral Fellowship, and the German Federal Ministry of Science and Education (Young Investigators Group CoSy-CC2, grant no. 01LN1306A). J.F.D. thanks the Stordalen Foundation and BMBF (project GLUES) for financial support. D.H. has been funded by grant ERC-CZ CORES LL-1201 of the Czech Ministry of Education. M.P. and N.J. received funding from the Czech Science Foundation project No. P303-14-02634S and from the Czech Ministry of Education, Youth and Sports, project No. DAAD-15-30. J.H. was supported by the Czech Science Foundation project GA13-23940S and Czech Health Research Council project NV15-29835A. We thank Mary Lindsey from the National Oceanic and Atmospheric Administration for her kind help with Fig. 4e. NCEP Reanalysis data provided by NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their web site at http://www.esrl.noaa.gov/psd/.Peer reviewedPublisher PD

Online System for Fire Danger Rating in Colorado

A method for the data assimilation of fuel moisture surface observations has been developed for the purpose of incorporation in wildfire forecasting and fire danger rating. In this work, we describe the method itself and also an online computer system that implements the method and combines it with the Real-Time Mesoscale Analysis to track local weather conditions and estimate the fuel moisture content in the state of Colorado. We discuss the construction of the system and future development