6.  Belu, R. and D. Koračin: Regional analysis of wind velocity patterns in complex terrain.

Wind energy is a weather and climate-dependent energy resource with natural spatio-temporal variabilities at time scales ranging from fraction of seconds to seasons and years, while at spatial scales it is strongly affected by the terrain and vegetation. To optimize wind energy systems and maximize the energy extraction, wind measurements on various time scales as well as wind energy forecasts are required and needed. This study focuses on spatio-temporal characteristics of the wind velocity in complex terrain, relevant to wind energy assessment, operation, and grid integration, using data collected at 11 towers ranging from 40 to 80 m tall over a 12-year period in complex terrain of western-central and northern Nevada, USA. The autocorrelation analysis, Detrended Fluctuation Analysis (DFA) and Detrended Cross-Correlation Analysis (DCCA) showed strong coherence between the wind speed and direction with slowly decreasing amplitude of the multi-day periodicity with increasing lag periods. Besides pronounced diurnal periodicity at all locations, statistical analysis and DFA also showed significant seasonal and annual periodicities, long-memory persistence with similar characteristics at all sites and towers with a relatively narrow range of the Weibull parameters. The DCCA indicates similar wind patterns at each tower, and strong correlations between measurement sites in spite of separations of about 300 km across the towers' setup. The northern Nevada area exhibits higher wind resource potential and higher wind persistence compared to the western-central region. Overall, the DFA and DCCA results suggest higher degree of complementarity among wind data at measurement sites compared to previous standard statistical analysis.

Keywords: wind towers, wind energy, wind resource assessment, detrended fluctuation analysis, wind regime, autocorrelation analysis, detrended cross-correlation analysis

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7.  Jędruszkiewicz, J. and J. Wibig: General overview of the potential effect of extreme temperature change on society and economy in Poland in the 21st century.

This work gives an overview on how the projected changes in the extremes in Poland might impact human health and economy. For that purpose, statistically corrected data from 7 regional climate models were used. A significant increase of extreme hot events (i.e. heat waves, tropical nights) is projected for Central and Southern Poland for the end of the 21st century which might seriously affect a society living in large urban areas. Less extreme cold events improve thermal comfort in winter. The negative impact of the warming will affect energy systems with higher demand for electricity in summer and agriculture: an earlier beginning of the growing season and flower blooming will enhance the risk of frost damages in spring, whereas excessive heat will reduce yields in summer. Polish tourism should benefit from higher thermal comfort (except for hot July and August in the far future and warming in the winter season bringing snow cover depletion in the near future).

Keywords: cold wave, heat wave, heating season, meteorological growing season, Poland, temperature extremes

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8.  Imashev, S., M. Mishchenko and M. Cheshev: Fractal analysis of seismoacoustic signals of near-surface sedimentary rocks in Kamchatka.

We studied, by the mono- and multifractal detrended fluctuation analysis (DFA), time fluctuations in the dynamics of seismoacoustic data, recorded in Karymshina site, which is located in a seismic area of Kamchatka. We took a series of seismoacoustic responses to the regional seismic events with the magnitudes M>4 for the period 2017-2018. The series was divided into three groups (high, medium and low) based on the amplitude of recorded seismoacoustic response. Background noise segments of the signals demonstrated monofractal behavior similar to white noise by almost constant values of generalized Hurst exponent Hq≈0.5 and very small width of the multifractal spectrum Δα≈0.1. Analysis of the high amplitude seismoacoustic signals with clear P-, S- and coda waves showed that P- and S-waves demonstrate wider multifractal spectrum (ΔαP=0.37, ΔαS=0.35) and range of generalized Hurst exponents Hq in comparison with coda wave, characterized by almost constant Hq and minimal width of multifractal spectrum (ΔαCODA=0.13). We showed that the properties of the multifractal spectrum could be used in detection of seismic wave arrival, estimation its duration and separation of P-, S- and coda waves. Application of the monofractal DFA in a sliding window showed that the acoustic signal transits from monofractal and uncorrelated background noise (Hurst exponent equals to 0.5) into the long-range dependent state during seismic waves arrival, that is helpful in analysis of the signals, particularly in case of low amplitude acoustic responses, usually demonstrating an unclear waveform. Difference in multifractal spectrum width between the original low amplitude signal and its surrogates, obtained by random shuffling showed that the multifractality in the signal is dominantly due to long-range correlations.

Keywords: seismoacoustic signal, monofractal, Hurst exponent, multifractal, detrended fluctuation analysis/span>

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