An Application of Low-Order Arma and Garch Models for Sea Level FluctuationsThe paper presents th... more An Application of Low-Order Arma and Garch Models for Sea Level FluctuationsThe paper presents the analysis of geographically-dependent irregular sea level fluctuations, often referred to as residual terms around deterministic signals, carried out by means of stochastic low-order autoregressive moving average (ARMA) and generalised autoregressive conditional heteroscedastic (GARCH) models. The gridded sea level anomaly (SLA) time series from TOPEX/Poseidon (T/P) and Jason-1 (J-1) satellite altimetry, commencing on 10th January 1993 and finishing on 14th July 2003, has been examined. The aforementioned models, limited to low-orders being combinations of 0,1 and 2, have been fitted to the SLA data. The root mean square and the Shapiro-Wilk test for the normal distribution have been used to calculate statistics of the residuals from these models. It has been found that autoregressive (AR) models as well as ARMA ones serve well the purpose of adequate modelling irregular sea level fluct...
ABSTRACT Systematic differences of pole coordinates determined by the very long baseline interfer... more ABSTRACT Systematic differences of pole coordinates determined by the very long baseline interferometry (VLBI) and satellite laser ranging (SLR) from Lageos techniques in 1984-86 have been investigated especially in the short periodic part of the spectrum of their variations. Short periodic variations of pole motion detected by the maximum entropy spectral analysis in the VLBI and SLR data which were computed with the Ormsby filter are in good agreement, indicating the existence of real short periodic oscillations of determined motion of the instantaneous pole. Elimination of the computed deterministic part of short periodic variations of pole coordinates diminishes standard deviations of pole coordinates. Similar short periodic oscillations were found in pole coordinates computed by the atmospheric excitation function.
<p>Nowadays, huge number of regions spread around the World are struggling ... more <p>Nowadays, huge number of regions spread around the World are struggling with the problem of water availability. Hence, the quality and quantity of continental water resources must be regularly controlled. Currently, land water components are monitored, among others by measuring their weight, type and density or analyzing the level of water in the stilling wells. However, due to the time-consuming nature of such measurements, information on each components monitoring is lacking in many areas. For 15 years, the information about global hydrological changes has been regularly examined using monthly gravity fields provided by Gravity Recovery and Climate Experiment (GRACE) mission. GRACE mission ended in October 2017 and almost a year later, the GRACE Follow‐On (GRACE-FO) mission was launched in May 2018. Bridging the gap between both GRACE missions is currently a large challenge. In the following study, we propose a new bridging approach based on remove-restore technique combined with an autoregressive model (AR); the latter is utilized for residuals. The residuals are obtained as differences between GRACE/GRACE-FO data and climatology defined by Total Water Storage (TWS) parameter for Global Land Data Assimilation System (GLDAS) hydrological model. Residual annual sine-curve and its 3 overtones are then subtracted with the use of Least Squares Estimation (LSE) method. We predict missing TWS values using backward-forward AR approach. We conduct the TWS forecasting in two stages: (1) based only on the values before the gap (forward approach) and (2) the values available after the gap (backward approach). In our study, to test the adopted approach, we generate artificial 11 months gap. Comparing TWS values from our technique to values from original GRACE data in testing gap, we obtain differences within ±90 cm with median equal to -8 cm. The extreme values are observed in Amazon, Southern Asia or Alaska. The analysis of ratio between GRACE minus GLDAS and GRACE minus predicted values shows that our approach is better than the hydrological model standalone for more than 70% of continental areas. In the case of natural gap between both GRACE generation mission, the misclosures in backward-forward prediction calculated between TWS values predicted by forward and backward approach is 10 cm. This represents approximately 20% of total signal for observed TWS in 53% areas of the World. The presentation will include a discussion on regional analysis upon the areas characterized with extreme water changes occurred in natural observation gap. Analysis shows that presented method is able to capture the occurrence of droughts or floods, but does not reflect its magnitude. The obtained results indicate that presented remove-restore AR approach can be utilized to forecast geophysical changes much better for regions characterized with insignificant seasonal hydrological effect.</p>
Earth’s crust deforms in various time and spatial resolutions. To estimate them, geodetic observa... more Earth’s crust deforms in various time and spatial resolutions. To estimate them, geodetic observations are widely employed and compared to geophysical models. In this research, we focus on the Earth’s crust deformations resulting from hydrology mass changes, as observed by GRACE (Gravity Recovery and Climate Experiment) gravity mission and modeled using WGHM (WaterGAP Global Hydrological Model) and GLDAS (Global Land Data Assimilation System), hydrological models. We use the newest release of GRACE Level-2 products, i. e. RL06, provided by the CSR (Center for Space Research, Austin) analysis center in the form of a mascon solution. The analysis is performed for the European area, divided into 29 river basins. For each basin, the average signal is estimated. Then, annual amplitudes and trends are calculated. We found that the eastern part of Europe is characterized by the largest annual amplitudes of hydrology-induced Earth’s crust deformations, which decrease with decreasing distanc...
The atmospheric surface pressure time series of Madras, Darwin, and Tahiti together with non-tida... more The atmospheric surface pressure time series of Madras, Darwin, and Tahiti together with non-tidal length-of-day (LODR) variations and axial component of atmospheric angular momentum (AAM) were analyzed by wavelet transform as well as the combination of the Fourier transform band pass filter with the Hilbert transform (FTBPF + HT) to detect interannual and intra-seasonal oscillations in them. It was found that annual oscillations in the atmospheric surface pressure variations of Darwin and Tahiti stations are in phase and are about 180o out of phase in the atmospheric surface pressure variations of Madras station. The phase of the annual oscillation in atmospheric surface pressure variations of Madras station is slightly greater (~ 20o) than the phase of the annual oscillation in the LODR time series. The amplitude and phase variations of the annual and semi-annual oscillations computed by the FTBPF + HT combination in LODR and the axial component of AAM are very similar. The mean a...
The Earth orientation parameters (EOP) are determined by space geodetic techniques with very high... more The Earth orientation parameters (EOP) are determined by space geodetic techniques with very high accuracy. However, the accuracy of their prediction, even for a few days in the future, is several times lower and still unsatisfactory for practical use. The main problem of each prediction technique is to predict simultaneously long and short period oscillations of the EOP. It has been shown that the combination of the prediction methods which are different for deterministic and stochastic components of the EOP can provide the best accuracy of prediction. Several prediction techniques, e.g. combination of the least-squares with autoregressive and autocovariance methods as well as combination of wavelet transform decomposition and autocovariance prediction, were used to predict x, y pole coordinates in polar coordinate system and UT 1− UTC or length of day (∆) data. Different prediction algorithms were compared considering the difference between the EOP data and their predictions at di...
Gridded sea level anomaly time series from TOPEX/Poseidon and Jason-1 satellite altimetry have be... more Gridded sea level anomaly time series from TOPEX/Poseidon and Jason-1 satellite altimetry have been processed in order to detect nonlinearity of sea level change in the period 1993-2003. Basic statistics, such as standard deviation, skewness and kurtosis, along with testing hypothesis served well the purpose of statistical evaluation. The data obtained by both satellites have been merged by applying the offset between two time series, separately for each location grid. In order to infer nonlinear features of sea level variation, four specific terms (linear trend, annual oscillation, semiannual component and alias-type 62-days oscillation) have been removed from the merged time series for each grid. It has been shown that the particularly meaningful departures from the normal distribution of sea level change are present within the equatorial zone in the Pacific and Indian Oceans. This finding has been associated with the asymmetry between strengths of El Niño and La Niña episodes. Th...
The problems related to sea level fluctuations are in the scope of Global Geodetic Observing Syst... more The problems related to sea level fluctuations are in the scope of Global Geodetic Observing System (GGOS) project. The essential and highly unpredictable reason of regional sea level change in the equatorial Pacific is El Nino/Southern Osciallation (ENSO). El Nino event causes an increase in sea level in the vicinity of the east equatorial Pacific, whereas La Nina phenomenon leads to the decrease in the sea level in this region. We examined the sea level anomaly (SLA) data from TOPEX/Poseidon altimetry in the period 1992-2002. The study focuses on forecasting SLA data in the rectangular area: 20 S - 20 N, 70 W - 130 W covering the equatorial sections of west coasts of South, Middle, and North America. First, the polynomial-harmonic least-squares model (LS) consisted of annual, semiannual oscillations and the linear trend was extrapolated. Second, the above mentioned extrapolation was combined with the autoregressive prediction (LS+AR) of stochastic SLA residuals. The second approac...
The mean observational error of UT1-UTC is now of the order of 0.006 ms, which corresponds to abo... more The mean observational error of UT1-UTC is now of the order of 0.006 ms, which corresponds to about 2.8 mm on the Earth’s surface. Usually the prediction error even for a few days in the future is several times greater than the observational error. In this paper different stochastic prediction techniques including autocovariance, autoregressive, autoregressive moving average, and neural networks were applied to predict UT1-UTC IERS EOPC04 data (IERS 2004). All known effects such as leap seconds and solid Earth zonal tides (McCarthy and Petit 2003) were first removed from the observed values of UT1-UTC. To predict the LODR time series the combination of the least-squares (LS) extrapolation with different stochastic prediction methods was applied. The results of the combination of the LS extrapolation with different stochastic prediction techniques were compared with the results of the UT1-UTC prediction method currently used by the IERS Rapid Service/Prediction Centre.
The summary of research activities concerning general theory and methodology performed in Poland ... more The summary of research activities concerning general theory and methodology performed in Poland in the period of 2015–2018 is presented as a national report for the 27th IUGG (International Union of Geodesy and Geophysics) General Assembly. It contains the results of research on new or improved methods and variants of robust parameter estimation and their application, especially to control network analysis. Reliability analysis of the observation system and an integrated adjustment approach are also given. The identifiability (ID) index as a new measure for minimal detectable bias (MDB) in the observation system of a network, has been introduced. A new method of covariance function parameter estimation in the least squares collocation has been developed. The robustified version of the Shift-Msplit estimation, termed as Shift-M*split estimation, which enables estimation of parameter differences (robustly), without the need of prior estimation of the parameters, has been introduced. ...
The non-tidal LOD data are analysed (data span 01.01.1962-09.01.2008) in order to provide the pro... more The non-tidal LOD data are analysed (data span 01.01.1962-09.01.2008) in order to provide the probabilistic characteristics of the Earth rotation rate fluctuations. The skewness of the LOD probability distribution is of -0.31 indicating that the probability distribution is asymmetrical. Moreover, the residual non-tidal LOD data is considered (after removal of the semiannual, annual, 9.3-years, and 18.6-years oscillations, and linear trend). The skewness of this residual data equals to -0.64 and indicates an increased asymmetry in the distribution. For the non-transformed LOD data the kurtosis is of 2.31 and it shows that the distribution is flattened. The kurtosis for the residuals is 5.64 indicating that the distribution is more peaked than a normal distribution. For the non-transformed LOD data, the Jonhson SB distribution provides the best fit. For the residual LOD data, the Johnson SU distribution is found to be the most appropriate model. Both the LOD and it’s residual time ser...
In this paper the three spectro-temporal analyses: the Fourier Transform Band Pass Filter (FTBPF)... more In this paper the three spectro-temporal analyses: the Fourier Transform Band Pass Filter (FTBPF), the Wavelet Transform (WT) and Harmonic Wavelet Transform (HWT) are compared on short period Earth Rotation Parameters (ERP) and the Atmospheric Angular Momentum (AAM) data. The computed time variable and time-frequency spectra of length of day (LOD) data reveal various effects of changing the time and frequency resolution in the FTBPF and frequency resolution in the HWT spectra.
The x, y pole coordinates model data were computed by numerical integration of differential equat... more The x, y pole coordinates model data were computed by numerical integration of differential equation of polar motion using equatorial components of atmospheric, ocean, hydrologic excitation functions and their sums. Other x, y pole coordinates model data were obtained by summing different frequency components determined by the discrete wavelet transform band pass filter (DWTBPF). The IERS pole coordinates data and the pole coordinates model data were then predicted by the combination of the least-squares (LS) model extrapolation and autoregressive (AR) prediction (LS+AR). Comparison of the prediction errors of the IERS pole coordinates data and the pole coordinates model data, computed at different starting prediction epochs, has enabled examination of the influence of wide-band oscillations present in the IERS pole coordinates data as well as the fluid excitation functions on the prediction errors of the IERS pole coordinates data.
ZARYS TREŚCI: Prognozy parametrów orientacji Ziemi potrzebne są do wyznaczenia w czasie rzeczywis... more ZARYS TREŚCI: Prognozy parametrów orientacji Ziemi potrzebne są do wyznaczenia w czasie rzeczywistym transformacji pomiędzy niebieskim i ziemskim układem odniesienia. W pracy przedstawione zostały różne metody prognozowania współrzędnych x, y bieguna ziemskiego i czasu UT1 – UTC, takie jak metoda najmniejszych kwadratów (LS), autoregresji (AR), autoregresji i średniej ruchomej (ARMA), autokowariancji (AC), sieci neuronowych (NN), a także kombinacje metody LS z metodami AR, ARMA, AC i NN. Przedstawiona została także metoda prognozowania współrzędnych bieguna ziemskiego w układzie współrzędnych biegunowych. Najwyższą dokładność prognozy współrzędnych bieguna ziemskiego uzyskuje się poprzez zastosowanie kombinacji metody LS z metodą AR (LS+AR). Błędy prognozy współrzędnych bieguna ziemskiego są mniejsze niż dla metody prognozowania obecnie stosowanej przez IERS Rapid Service/Prediction Centre w USNO. Prognozy metodą LS+AR współrzędnych bieguna ziemskiego są raz na tydzień automatycznie...
An Application of Low-Order Arma and Garch Models for Sea Level FluctuationsThe paper presents th... more An Application of Low-Order Arma and Garch Models for Sea Level FluctuationsThe paper presents the analysis of geographically-dependent irregular sea level fluctuations, often referred to as residual terms around deterministic signals, carried out by means of stochastic low-order autoregressive moving average (ARMA) and generalised autoregressive conditional heteroscedastic (GARCH) models. The gridded sea level anomaly (SLA) time series from TOPEX/Poseidon (T/P) and Jason-1 (J-1) satellite altimetry, commencing on 10th January 1993 and finishing on 14th July 2003, has been examined. The aforementioned models, limited to low-orders being combinations of 0,1 and 2, have been fitted to the SLA data. The root mean square and the Shapiro-Wilk test for the normal distribution have been used to calculate statistics of the residuals from these models. It has been found that autoregressive (AR) models as well as ARMA ones serve well the purpose of adequate modelling irregular sea level fluct...
ABSTRACT Systematic differences of pole coordinates determined by the very long baseline interfer... more ABSTRACT Systematic differences of pole coordinates determined by the very long baseline interferometry (VLBI) and satellite laser ranging (SLR) from Lageos techniques in 1984-86 have been investigated especially in the short periodic part of the spectrum of their variations. Short periodic variations of pole motion detected by the maximum entropy spectral analysis in the VLBI and SLR data which were computed with the Ormsby filter are in good agreement, indicating the existence of real short periodic oscillations of determined motion of the instantaneous pole. Elimination of the computed deterministic part of short periodic variations of pole coordinates diminishes standard deviations of pole coordinates. Similar short periodic oscillations were found in pole coordinates computed by the atmospheric excitation function.
<p>Nowadays, huge number of regions spread around the World are struggling ... more <p>Nowadays, huge number of regions spread around the World are struggling with the problem of water availability. Hence, the quality and quantity of continental water resources must be regularly controlled. Currently, land water components are monitored, among others by measuring their weight, type and density or analyzing the level of water in the stilling wells. However, due to the time-consuming nature of such measurements, information on each components monitoring is lacking in many areas. For 15 years, the information about global hydrological changes has been regularly examined using monthly gravity fields provided by Gravity Recovery and Climate Experiment (GRACE) mission. GRACE mission ended in October 2017 and almost a year later, the GRACE Follow‐On (GRACE-FO) mission was launched in May 2018. Bridging the gap between both GRACE missions is currently a large challenge. In the following study, we propose a new bridging approach based on remove-restore technique combined with an autoregressive model (AR); the latter is utilized for residuals. The residuals are obtained as differences between GRACE/GRACE-FO data and climatology defined by Total Water Storage (TWS) parameter for Global Land Data Assimilation System (GLDAS) hydrological model. Residual annual sine-curve and its 3 overtones are then subtracted with the use of Least Squares Estimation (LSE) method. We predict missing TWS values using backward-forward AR approach. We conduct the TWS forecasting in two stages: (1) based only on the values before the gap (forward approach) and (2) the values available after the gap (backward approach). In our study, to test the adopted approach, we generate artificial 11 months gap. Comparing TWS values from our technique to values from original GRACE data in testing gap, we obtain differences within ±90 cm with median equal to -8 cm. The extreme values are observed in Amazon, Southern Asia or Alaska. The analysis of ratio between GRACE minus GLDAS and GRACE minus predicted values shows that our approach is better than the hydrological model standalone for more than 70% of continental areas. In the case of natural gap between both GRACE generation mission, the misclosures in backward-forward prediction calculated between TWS values predicted by forward and backward approach is 10 cm. This represents approximately 20% of total signal for observed TWS in 53% areas of the World. The presentation will include a discussion on regional analysis upon the areas characterized with extreme water changes occurred in natural observation gap. Analysis shows that presented method is able to capture the occurrence of droughts or floods, but does not reflect its magnitude. The obtained results indicate that presented remove-restore AR approach can be utilized to forecast geophysical changes much better for regions characterized with insignificant seasonal hydrological effect.</p>
Earth’s crust deforms in various time and spatial resolutions. To estimate them, geodetic observa... more Earth’s crust deforms in various time and spatial resolutions. To estimate them, geodetic observations are widely employed and compared to geophysical models. In this research, we focus on the Earth’s crust deformations resulting from hydrology mass changes, as observed by GRACE (Gravity Recovery and Climate Experiment) gravity mission and modeled using WGHM (WaterGAP Global Hydrological Model) and GLDAS (Global Land Data Assimilation System), hydrological models. We use the newest release of GRACE Level-2 products, i. e. RL06, provided by the CSR (Center for Space Research, Austin) analysis center in the form of a mascon solution. The analysis is performed for the European area, divided into 29 river basins. For each basin, the average signal is estimated. Then, annual amplitudes and trends are calculated. We found that the eastern part of Europe is characterized by the largest annual amplitudes of hydrology-induced Earth’s crust deformations, which decrease with decreasing distanc...
The atmospheric surface pressure time series of Madras, Darwin, and Tahiti together with non-tida... more The atmospheric surface pressure time series of Madras, Darwin, and Tahiti together with non-tidal length-of-day (LODR) variations and axial component of atmospheric angular momentum (AAM) were analyzed by wavelet transform as well as the combination of the Fourier transform band pass filter with the Hilbert transform (FTBPF + HT) to detect interannual and intra-seasonal oscillations in them. It was found that annual oscillations in the atmospheric surface pressure variations of Darwin and Tahiti stations are in phase and are about 180o out of phase in the atmospheric surface pressure variations of Madras station. The phase of the annual oscillation in atmospheric surface pressure variations of Madras station is slightly greater (~ 20o) than the phase of the annual oscillation in the LODR time series. The amplitude and phase variations of the annual and semi-annual oscillations computed by the FTBPF + HT combination in LODR and the axial component of AAM are very similar. The mean a...
The Earth orientation parameters (EOP) are determined by space geodetic techniques with very high... more The Earth orientation parameters (EOP) are determined by space geodetic techniques with very high accuracy. However, the accuracy of their prediction, even for a few days in the future, is several times lower and still unsatisfactory for practical use. The main problem of each prediction technique is to predict simultaneously long and short period oscillations of the EOP. It has been shown that the combination of the prediction methods which are different for deterministic and stochastic components of the EOP can provide the best accuracy of prediction. Several prediction techniques, e.g. combination of the least-squares with autoregressive and autocovariance methods as well as combination of wavelet transform decomposition and autocovariance prediction, were used to predict x, y pole coordinates in polar coordinate system and UT 1− UTC or length of day (∆) data. Different prediction algorithms were compared considering the difference between the EOP data and their predictions at di...
Gridded sea level anomaly time series from TOPEX/Poseidon and Jason-1 satellite altimetry have be... more Gridded sea level anomaly time series from TOPEX/Poseidon and Jason-1 satellite altimetry have been processed in order to detect nonlinearity of sea level change in the period 1993-2003. Basic statistics, such as standard deviation, skewness and kurtosis, along with testing hypothesis served well the purpose of statistical evaluation. The data obtained by both satellites have been merged by applying the offset between two time series, separately for each location grid. In order to infer nonlinear features of sea level variation, four specific terms (linear trend, annual oscillation, semiannual component and alias-type 62-days oscillation) have been removed from the merged time series for each grid. It has been shown that the particularly meaningful departures from the normal distribution of sea level change are present within the equatorial zone in the Pacific and Indian Oceans. This finding has been associated with the asymmetry between strengths of El Niño and La Niña episodes. Th...
The problems related to sea level fluctuations are in the scope of Global Geodetic Observing Syst... more The problems related to sea level fluctuations are in the scope of Global Geodetic Observing System (GGOS) project. The essential and highly unpredictable reason of regional sea level change in the equatorial Pacific is El Nino/Southern Osciallation (ENSO). El Nino event causes an increase in sea level in the vicinity of the east equatorial Pacific, whereas La Nina phenomenon leads to the decrease in the sea level in this region. We examined the sea level anomaly (SLA) data from TOPEX/Poseidon altimetry in the period 1992-2002. The study focuses on forecasting SLA data in the rectangular area: 20 S - 20 N, 70 W - 130 W covering the equatorial sections of west coasts of South, Middle, and North America. First, the polynomial-harmonic least-squares model (LS) consisted of annual, semiannual oscillations and the linear trend was extrapolated. Second, the above mentioned extrapolation was combined with the autoregressive prediction (LS+AR) of stochastic SLA residuals. The second approac...
The mean observational error of UT1-UTC is now of the order of 0.006 ms, which corresponds to abo... more The mean observational error of UT1-UTC is now of the order of 0.006 ms, which corresponds to about 2.8 mm on the Earth’s surface. Usually the prediction error even for a few days in the future is several times greater than the observational error. In this paper different stochastic prediction techniques including autocovariance, autoregressive, autoregressive moving average, and neural networks were applied to predict UT1-UTC IERS EOPC04 data (IERS 2004). All known effects such as leap seconds and solid Earth zonal tides (McCarthy and Petit 2003) were first removed from the observed values of UT1-UTC. To predict the LODR time series the combination of the least-squares (LS) extrapolation with different stochastic prediction methods was applied. The results of the combination of the LS extrapolation with different stochastic prediction techniques were compared with the results of the UT1-UTC prediction method currently used by the IERS Rapid Service/Prediction Centre.
The summary of research activities concerning general theory and methodology performed in Poland ... more The summary of research activities concerning general theory and methodology performed in Poland in the period of 2015–2018 is presented as a national report for the 27th IUGG (International Union of Geodesy and Geophysics) General Assembly. It contains the results of research on new or improved methods and variants of robust parameter estimation and their application, especially to control network analysis. Reliability analysis of the observation system and an integrated adjustment approach are also given. The identifiability (ID) index as a new measure for minimal detectable bias (MDB) in the observation system of a network, has been introduced. A new method of covariance function parameter estimation in the least squares collocation has been developed. The robustified version of the Shift-Msplit estimation, termed as Shift-M*split estimation, which enables estimation of parameter differences (robustly), without the need of prior estimation of the parameters, has been introduced. ...
The non-tidal LOD data are analysed (data span 01.01.1962-09.01.2008) in order to provide the pro... more The non-tidal LOD data are analysed (data span 01.01.1962-09.01.2008) in order to provide the probabilistic characteristics of the Earth rotation rate fluctuations. The skewness of the LOD probability distribution is of -0.31 indicating that the probability distribution is asymmetrical. Moreover, the residual non-tidal LOD data is considered (after removal of the semiannual, annual, 9.3-years, and 18.6-years oscillations, and linear trend). The skewness of this residual data equals to -0.64 and indicates an increased asymmetry in the distribution. For the non-transformed LOD data the kurtosis is of 2.31 and it shows that the distribution is flattened. The kurtosis for the residuals is 5.64 indicating that the distribution is more peaked than a normal distribution. For the non-transformed LOD data, the Jonhson SB distribution provides the best fit. For the residual LOD data, the Johnson SU distribution is found to be the most appropriate model. Both the LOD and it’s residual time ser...
In this paper the three spectro-temporal analyses: the Fourier Transform Band Pass Filter (FTBPF)... more In this paper the three spectro-temporal analyses: the Fourier Transform Band Pass Filter (FTBPF), the Wavelet Transform (WT) and Harmonic Wavelet Transform (HWT) are compared on short period Earth Rotation Parameters (ERP) and the Atmospheric Angular Momentum (AAM) data. The computed time variable and time-frequency spectra of length of day (LOD) data reveal various effects of changing the time and frequency resolution in the FTBPF and frequency resolution in the HWT spectra.
The x, y pole coordinates model data were computed by numerical integration of differential equat... more The x, y pole coordinates model data were computed by numerical integration of differential equation of polar motion using equatorial components of atmospheric, ocean, hydrologic excitation functions and their sums. Other x, y pole coordinates model data were obtained by summing different frequency components determined by the discrete wavelet transform band pass filter (DWTBPF). The IERS pole coordinates data and the pole coordinates model data were then predicted by the combination of the least-squares (LS) model extrapolation and autoregressive (AR) prediction (LS+AR). Comparison of the prediction errors of the IERS pole coordinates data and the pole coordinates model data, computed at different starting prediction epochs, has enabled examination of the influence of wide-band oscillations present in the IERS pole coordinates data as well as the fluid excitation functions on the prediction errors of the IERS pole coordinates data.
ZARYS TREŚCI: Prognozy parametrów orientacji Ziemi potrzebne są do wyznaczenia w czasie rzeczywis... more ZARYS TREŚCI: Prognozy parametrów orientacji Ziemi potrzebne są do wyznaczenia w czasie rzeczywistym transformacji pomiędzy niebieskim i ziemskim układem odniesienia. W pracy przedstawione zostały różne metody prognozowania współrzędnych x, y bieguna ziemskiego i czasu UT1 – UTC, takie jak metoda najmniejszych kwadratów (LS), autoregresji (AR), autoregresji i średniej ruchomej (ARMA), autokowariancji (AC), sieci neuronowych (NN), a także kombinacje metody LS z metodami AR, ARMA, AC i NN. Przedstawiona została także metoda prognozowania współrzędnych bieguna ziemskiego w układzie współrzędnych biegunowych. Najwyższą dokładność prognozy współrzędnych bieguna ziemskiego uzyskuje się poprzez zastosowanie kombinacji metody LS z metodą AR (LS+AR). Błędy prognozy współrzędnych bieguna ziemskiego są mniejsze niż dla metody prognozowania obecnie stosowanej przez IERS Rapid Service/Prediction Centre w USNO. Prognozy metodą LS+AR współrzędnych bieguna ziemskiego są raz na tydzień automatycznie...
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