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Short-term prediction of UT1-UTC and LOD via Dynamic Mode Decomposition and combination of least-squares and vector autoregressive model

Michalczak Maciej, Ligas Marcin

Reports on Geodesy and Geoinformatics

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2024

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Vol. 117

45--54

EN

This study presents a short-term forecast of UT1-UTC and LOD using two methods, i.e. Dynamic Mode Decomposition (DMD) and combination of Least-Squares and Vector Autoregression (LS+VAR). The prediction experiments were performed separately for yearly time spans, 2018-2022. The prediction procedure started on January 1 and ended on December 31, with 7-day shifts between subsequent 30-day forecasts. Atmospheric Angular Momentum data (AAM) were used as an auxiliary time series to potentially improve the prediction accuracy of UT1-UTC and LOD in LS+VAR procedure. An experiment was also conducted with and without elimination of effect of zonal tides from UT1-UTC and LOD time series. Two approaches to using the best steering parameters for the methods were applied:. First, an adaptive approach, which observes the rule that before every single forecast, a preliminary one must be performed on the pre-selected sets of parameters, and the one with the smallest prediction error is then used for the final prediction; and second, an averaged approach, whereby several forecasts are made with different sets of parameters (the same parameters as in adaptive approach) and the final values are calculated as the averages of these predictions. Depending on the method and data combination mean absolute prediction errors (MAPE) for UT1-UTC vary from 0.63 ms to 1.43 ms for the 10th day and from 3.07 ms to 8.05 ms for the 30th day of the forecast. Corresponding values for LOD vary from 0.110 ms to 0.245 ms for the 10th day and from 0.148 ms to 0.325 ms for the 30th day.

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Wzrost i kwitnienie czosnku (Allium L.) ‘Ivory Queen’ pędzonego w warunkach sztucznego oświetlenia

Krzymińska A., Śmigielska M., Juszczyk R.

Polish Journal for Sustainable Development

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2017

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T. 21, cz. 2

77--82

PL

Celem doświadczenia było określenie wpływu barwy światła na pędzenie czosnku ‘Ivory Queen’. Chłodzenie cebul rozpoczęto 18 października 2007 roku. Po 11,5 tygodniach cebule posadzono do doniczek i kontynuowano chłodzenie. Łączny czas chłodzenia cebul wynosił 20 tygodni. Rośliny przeniesiono do pokoju wzrostowego 6 marca 2008 roku i ustawiono na regałach oświetlanych światłem białym, niebieskim, zielonym, żółtym i czerwonym przez 6 lub 12 godzin dziennie. Natężenie napromienienia kwantowego wynosiło 12,5 μmol m-2 s-1. Wyniki wskazują, że czosnek ‘Ivory Queen’ można pędzić w doniczkach stosując światło niebieskie przez 12 godzin dziennie.

EN

The purpose of the following study was to determine the influence of the light colour onto the forcing of Allium ‘Ivory Queen’. The bulbs cooling was commenced on the 18th of October 2007. After 11.5 weeks the bulbs were planted into pots and the cooling continued. Joint cooling time was 20 weeks. The plants were transferred to the growth room on the 6th March 2008 and were placed on the shelves under the white, blue, green, yellow and red colour light for 6 or 12 hours a day. The quantum irradiance was 12,5 μmol m-2 s-1. The obtained results indicate that Allium ‘Ivory Queen’ can be forced in pots under the blue light for 12 hours a day.

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Ecological importance of seed dimorphism in corn spurry (Spergula arvensis L.) 1. The effects of day length on seed germinability

Kucewicz M., Gojło E.

Polish Journal of Ecology

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2013

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Vol. 61, nr 4

665--673

EN

Spergula arvensis L. (corn spurry) is a heteromorphic species of the Caryophyllaceae family, that produces two types of seeds with a smooth (non papillate, NP) or papillate (P) coat. The plant flowers and produces fruit between May and September, a period marked by a gradual decrease in day length. The objective of this study was to determine the effects of day length on the germinability of heteromorphic seeds. In addition, we examined the frequencies of non papillate and papillate seeds in four populations. Germination tests were performed on seeds harvested from plants grown in a greenhouse under conditions simulating long days (17 hour photoperiod) and short days (12 hour photoperiod). Heteromorphic seeds incubated in water at various temperatures (10–30°C) over a period of 4 weeks remained dormant. Corn spurry seeds had different responses to the addition of nitrate after four weeks of pre-treatment. Both seed morphs kept at a temperature of 10–20°C did not germinate or their germination rates did not exceed 6%. Seeds incubated at 25°C and 30°C broke dormancy. NP seeds from plants growing under long- and short-day photoperiods were characterized by higher germinability than P seeds at both temperatures. The above-mentioned results indicate that variations in light exposure during plant growth and development do not contribute to somatic heteromorphism of S. arvensis seeds. Day length has no significant effect on the germination of heteromorphic seeds.The populations were heteromorphic with respect to plants having papillate seeds and plants having non papillate seeds. The majority of individuals were monomorphic and produced capsules containing only one type of seed. Heteromorphic individuals produced capsules containing: a) NP seeds, and b) P seeds, and c) mixed seeds. The analyzed populations were characterized by a predominance of P seeds in the overall seed pool.