Analyses of zonal atmospheric excitation functions and their correlation with polar motion excitation functions

International audienceThe atmospheric influence on the Earth's, rotation can be described by the effective atmospheric angular momentum (EAAM) functions. In this study we focus on the analysis of short period variations of the equatorial components of the zonal EAAM excitation functions ?1 and ?2 and their influence on similar variations of polar motion. The global objective analysis data of the Japanese Meteorological Agency for the period 1986?1992 were used to compute the EAAM excitation functions in different latitude belts. Time- and latitude-variable amplitude spectra of variations of these functions with periods shorter than 150 days, containing pressure, pressure with the inverted barometric correction, and wind terms were computed. The spectra show distinct latitude and time variations of the prograde and retrograde oscillations which reach their maxima mainly in mid-latitudes. Prograde and retrograde oscillations with periods of about 40?60 days and about 110?120 days are seen in the spectra of pressure terms of the equatorial components of the zonal EAAM excitation functions. Additionally, correlation coefficients and cross-spectra between variations of the geodetic polar motion and equatorial components of the zonal EAAM excitation functions were computed to identify the latitude belts of the globe over which atmospheric circulation changes are correlated mostly with short period variations of the polar motion excitation functions. The correlation coefficients vary in time and latitude and reach maximum values in the northern latitudes from 50°N to 60°N. In the cross-spectra between the polar motion excitation functions and pressure terms of the zonal EAAM excitation functions there are peaks of common prograde oscillations with the periods around 20, 30, 40?50, 60 and 80?150 days and of common retrograde oscillations around 20, 30, 40 and 50?70 days

Status of Women in Astronomy: A need for advancing inclusivity and equal opportunities

Women in the Astronomy and STEM fields face systemic inequalities throughout their careers. Raising awareness, supported by detailed statistical data, represents the initial step toward closely monitoring hurdles in career progress and addressing underlying barriers to workplace equality. This, in turn, contributes to rectifying gender imbalances in STEM careers. The International Astronomical Union Women in Astronomy (IAU WiA) working group, a part of the IAU Executive Committee, is dedicated to increasing awareness of the status of women in Astronomy and supporting the aspirations of female astronomers globally. Its mission includes taking concrete actions to advance equal opportunities for both women and men in the field of astronomy. In August 2021, the IAU WiA Working Group established a new organizing committee, unveiling a comprehensive four-point plan. This plan aims to strengthen various aspects of the group's mission, encompassing: (i) Awareness Sustainability: Achieved through surveys and data collection, (ii) Training and Skill Building: Focused on professional development, (iii) Fundraising: To support key initiatives, and (iv) Communication: Dissemination of results through conferences, WG Magazines, newsletters, and more. This publication provides an overview of focused surveys that illuminate the factors influencing the careers of women in Astronomy, with a particular focus on the careers of mothers. It highlights the lack of inclusive policies, equal opportunities, and funding support for women researchers in the field. Finally, we summarize the specific initiatives undertaken by the IAU WiA Working Group to advance inclusivity and equal opportunities in Astronomy.Comment: 5 pages, 2 figure

Free polar motion of a triaxial and elastic body in Hamiltonian formalism: Application to the Earth and Mars

The purpose of this paper is to show how to solve in Hamiltonian formalism the equations of the polar motion of any arbitrarily shaped elastic celestial body, i.e. the motion of its rotation axis ( or angular momentum) with respect to its figure axis. With this aim, we deduce from canonical equations related to the rotational Hamiltonian of the body, the analytical solution for its free polar motion which depends both on the elasticity and on its moments of inertia. In particular, we study the influence of the phase angle delta, responsible for the dissipation, on the damping of the polar motion. In order to validate our analytical equations, we show that, to first order, they are in complete agreement with those obtained from the classical Liouville equations. Then we adapt our calculations to the real data obtained from the polar motion of the Earth (polhody). For that purpose, we characterize precisely the differences in radius J - chi and in angle l - theta between the polar coordinates (chi, theta) and ( J, l) representing respectively the motion of the axis of rotation of the Earth and the motion of its angular momentum axis, with respect to an Earth-fixed reference frame, after showing the influence of the choice of the origin on these coordinates, and on the determination of the Chandler period as well. Then we show that the phase lag delta responsible for the damping for the selected time interval, between Feb. 1982 and Apr. 1990, might be of the order of delta approximate to 6degrees, according to a numerical integration starting from our analytical equations. Moreover, we emphasize the presence in our calculations for both. and., of an oscillation with a period T(Chandler)/2, due to the triaxial shape of our planet, and generally not taken into account. In a last step, we apply our analytical formulation to the polar motion of Mars, thus showing the high dependence of its damping on the poorly known value of its Love number k. Moreover we emphasize the large oscillations of Mars' polar motion due to the triaxiality of this planet

Short periodic variations of polar motion and hemispheric atmospheric angular momentum excitation functions in the period 1984-1992

Short periodic oscillations with the periods from 10 up to 110 days of the hemispheric components of effective atmospheric angular momentum (EAAM) excitation function and their correlation with polar motion excitation function have been analyzed. The EAAM data of the Japan Meteorological Agency (JMA) computed for the two hemispheres and the very long baseline interferometry (VLBI) polar motion NGS 92 R01 data (NGS 1992), determined by the National Geodetic Survey were applied. The distinct oscillations with periods of about 28, 35-55 and 60-80 days were detected in the χy-component of both polar motion excitation function and northern EAAM excitation functions containing wind and pressure, with and without inverted barometric correction terms. The χy-component of the polar motion excitation function is significanly correlated (correlation coefficient equal to 0.55-0.75) with the χy-components of the northern EAAM excitation functions mentioned above, which are mostly induced by the atmospheric circulation over lands. No meaningful correlation between polar motion excitation function and the southern EAAM excitation functions was found. The χx-components of the EAAM and polar motion excitation functions are not significantly correlated. The strong short periodic variation of the length of day (LOD) and χy in the early 1988 seems to be caused by the above-mentioned 35-55 days oscillations of the northern hemisphere atmosphere. This variation can be related to the rapid passing from the El Niño to the La Niña phenomenon or from the minimum to the maximum in the Southern Oscillation Index in 1987-1989

Short periodic variations of polar motion and hemispheric atmospheric angular momentum excitation functions in the period 1984-1992

Short periodic oscillations with the periods from 10 up to 110 days of the hemispheric components of effective atmospheric angular momentum (EAAM) excitation function and their correlation with polar motion excitation function have been analyzed. The EAAM data of the Japan Meteorological Agency (JMA) computed for the two hemispheres and the very long baseline interferometry (VLBI) polar motion NGS 92 R01 data (NGS 1992), determined by the National Geodetic Survey were applied. The distinct oscillations with periods of about 28, 35-55 and 60-80 days were detected in the χ<sub><i>y</i></sub>-component of both polar motion excitation function and northern EAAM excitation functions containing wind and pressure, with and without inverted barometric correction terms. The χ<sub><i>y</i></sub>-component of the polar motion excitation function is significanly correlated (correlation coefficient equal to 0.55-0.75) with the χ<sub><i>y</i></sub>-components of the northern EAAM excitation functions mentioned above, which are mostly induced by the atmospheric circulation over lands. No meaningful correlation between polar motion excitation function and the southern EAAM excitation functions was found. The χ<sub><i>x</i></sub>-components of the EAAM and polar motion excitation functions are not significantly correlated. The strong short periodic variation of the length of day (<i>LOD</i>) and χ<sub><i>y</i></sub> in the early 1988 seems to be caused by the above-mentioned 35-55 days oscillations of the northern hemisphere atmosphere. This variation can be related to the rapid passing from the El Niño to the La Niña phenomenon or from the minimum to the maximum in the Southern Oscillation Index in 1987-1989

Chronology of Developments of Geodynamic Investigations in XIX and XX Centuries

There were big developments of geodynamic investigations in the XX century. In the paper the scope of the chronology of developments of geodynamic investigations from the end of XIX century until the beginning of XXI century is presented. It is presented in the following six areas: 1. Theory 2. Establishment of definitions and models 3. Analysis of observations 4. Celestial reference frames 5. Terrestrial reference frames 6. Organizations of investigation

GRACE signal filtering as a means of determining equivalent water thickness in Poland

In the paper an Equivalent Water Thickness (EWT) determination as a way of observing gravity variations is described. Since raw data acquired directly from Gravity Recovery and Climate Experiment – GRACE satellites is unsuitable for analysis due to stripes occurrence, a filtering algorithm must be used. In this paper, authors are testing two isotropic (Gauss, CNES/GRGS) filters and two anisotropic filters (Wiener-Kolomogorov, ANS). Correlation, amplitude ratio, and modification were determined as well as maps were generated

Local equivalent water thickness determination as a source of data for flood phenomenon observation

In the paper a flood phenomenon is analyzed. For this purpose data from GRACE satellites (Gravity Recovery and Climate Experiment) was used. Filtered data presented in a form of millimeters of Equivalent Water Thickness (EWT) was interpolated in places where flood in 2010 had happened (south of Poland). On a basis of graph where time series of EWT were presented, some conclusions were made. For the thesis confirmation meteorological WGHM and hydrological NOAA models were added to the GRACE model

Analyses of zonal atmospheric excitation functions and their correlation with polar motion excitation functions

The atmospheric influence on the Earth's, rotation can be described by the effective atmospheric angular momentum (EAAM) functions. In this study we focus on the analysis of short period variations of the equatorial components of the zonal EAAM excitation functions χ1 and χ2 and their influence on similar variations of polar motion. The global objective analysis data of the Japanese Meteorological Agency for the period 1986–1992 were used to compute the EAAM excitation functions in different latitude belts. Time- and latitude-variable amplitude spectra of variations of these functions with periods shorter than 150 days, containing pressure, pressure with the inverted barometric correction, and wind terms were computed. The spectra show distinct latitude and time variations of the prograde and retrograde oscillations which reach their maxima mainly in mid-latitudes. Prograde and retrograde oscillations with periods of about 40–60 days and about 110–120 days are seen in the spectra of pressure terms of the equatorial components of the zonal EAAM excitation functions. Additionally, correlation coefficients and cross-spectra between variations of the geodetic polar motion and equatorial components of the zonal EAAM excitation functions were computed to identify the latitude belts of the globe over which atmospheric circulation changes are correlated mostly with short period variations of the polar motion excitation functions. The correlation coefficients vary in time and latitude and reach maximum values in the northern latitudes from 50°N to 60°N. In the cross-spectra between the polar motion excitation functions and pressure terms of the zonal EAAM excitation functions there are peaks of common prograde oscillations with the periods around 20, 30, 40–50, 60 and 80–150 days and of common retrograde oscillations around 20, 30, 40 and 50–70 days