Assessing recently improved precession-nutation models 

2021 ◽  
Author(s):  
José M. Ferrándiz ◽  
Miguel A. Juárez ◽  
Santiago Belda ◽  
Tomás Baenas ◽  
Sadegh Modiri ◽  
...  
Keyword(s):  
Working Group ◽  
International Association ◽  
General Assembly ◽  
Fall Meeting ◽  
Individual Analysis ◽  
The Earth ◽  
Joint Working Group ◽  
Semi Empirical

<p>In 2020 new estimations of nutation amplitudes or precession parameters have been published or presented at main meetings. The derivation of corrections to improve the current precession-nutation models was encouraged by Resolution 5 of the 2019 General Assembly of the International Association of Geodesy (IAG). Besides, the GGOS/IERS Unified Analysis Workshop held in October 2019 recommended that effort to be prioritized among the tasks of the current IAU/IAG Joint Working Group on Improving Theories and Models of the Earth’s rotation (JWG ITMER).</p><p>This presentation is intended to present comparisons of some of those new semi-empirical and semi-theorical precession-nutation models developed by different authors from either VLBI solutions of individual analysis centers or combinations of them. The models recently introduced by the authors that were reported at the AGU 2020 Fall Meeting are included in this assessment.</p>

International Geomagnetic Reference Field, 1991 Revision: International Association of Geomagnetism and Aeronomy (IAGA) Division V, Working Group 8: Analysis of the main field and secular variation

Geophysics ◽  
1992 ◽  
Vol 57 (7) ◽  
pp. 956-956 ◽  
Author(s):  
R. A. Langel
Keyword(s):  
Secular Variation ◽  
Working Group ◽  
International Association ◽  
Legendre Function ◽  
Radial Distance ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
The Earth ◽  
International Geomagnetic Reference ◽  
Associated Legendre Function

The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation. Each model consists of a set of spherical harmonic (or Gauss) coefficients, g and h in a series expansion of the geomagnetic potential [Formula: see text], where a is the mean radius of the Earth (6371.2 km); r the radial distance from the center of the Earth; ϕ the east longitude measured from Greenwich; θ the geocentric colatitude; and [Formula: see text] the associated Legendre function of degree n and order m, normalized according to the convention of Schmidt [see, e.g., Langel (1987)]. In principle, N should be ∞ but the Working Group is of the opinion that in practice the available data for most epochs do not justify N greater than 10. This value is chosen to maintain consistency between models at different epochs. The coefficients are in units of nanotesla (nT).

scholarly journals IACS: past, present, and future of the International Association of Cryospheric Sciences

2019 ◽  
Vol 10 (1) ◽  
pp. 97-107
Author(s):  
Ian Allison ◽  
Charles Fierz ◽  
Regine Hock ◽  
Andrew Mackintosh ◽  
Georg Kaser ◽  
...  
Keyword(s):  
International Association ◽  
General Assembly ◽  
Earth System ◽  
10Th Anniversary ◽  
The Earth ◽  
History Of ◽  
New Association ◽  
International Geological ◽  
International Geological Congress ◽  
Key Events

Abstract. The International Association of Cryospheric Sciences (IACS) became the eighth and most recent association of IUGG at the general assembly in Perugia, Italy, in July 2007. IACS was launched in recognition of the importance of the cryosphere within the Earth system, particularly at a time of significant global change. It was the first new association of the union to be formed in over 80 years and IACS celebrated its 10th anniversary only a year before the IUGG centennial. The forbearers of IACS, however, stretch back even further than IUGG, starting with the formation of the Commission Internationale des Glaciers (CIG) by the International Geological Congress in 1894. Here we record the history of the transition from CIG to IACS, the scientific objectives that drove activities and changes, and some of the key events and individuals involved.

scholarly journals 4 Ephemerides (Ephemerides)

1991 ◽  
Vol 21 (1) ◽  
pp. 1-6
Keyword(s):  
Working Group ◽  
Reference System ◽  
Reference Frames ◽  
General Assembly ◽  
Reference Systems ◽  
The Earth ◽  
Astronomical Constants ◽  
Future Reference

This report covers the period from 1 July 1987 to 30 June 1990. The ephemerides that have been published during this period have made use of the system of astronomical constants adopted at the 16th General Assembly of the IAU in Grenoble. At the same time that the use of the FK5 system on the J2000 epoch is increasing and catalogues are becoming available for that system, there is an IAU Working Group on Reference Systems with subgroups on astronomical constants, nutation of the Earth, time and reference frames/origin. The purpose is to define a future reference system and resolve some of the difficulties that occur in the system. It is anticipated that this Working Group will develop recommendations for consideration at the 21st General Assembly of the IAU.

Effects of the observed Earth’s oblateness variation on precession-nutation: A first assessment

2020 ◽  
Author(s):  
José M. Ferrándiz ◽  
Alberto Escapa ◽  
Tomás Baenas ◽  
Santiago Belda ◽  
M. Isabel Vigo
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Time Variation ◽  
Earth Rotation ◽  
Working Group ◽  
International Association ◽  
Time Varying ◽  
Fundamental Issue ◽  
The Earth ◽  
Full Solution

<p>The current IAU2000 nutation theory considers the Earth’s dynamical ellipticity as a constant, whereas the IAU2006 precession theory uses a linear model for it. Apart from the problems of consistency between the two theories, whose full solution was proposed recently, the fundamental issue, namely whether the observed time variation of the Earth’s gravity field can affect the Earth’s rotation to a non-negligible extent or not, remains untreated.</p><p>This presentation is intended to share some preliminary results concerning precession and nutation. The variation of the Earth’s dynamical ellipticity is modelled from one of the time series providing the time-varying Stokes coefficients, and its effects on the longitude are computed following a new method introduced by the authors to that purpose. The found variations are above the accuracy goals of GGOS, the Global Geodetic Observing System of the International Association of Geodesy, adopted by its Joint Working Group on Improving theories and models of the Earth rotation (JWG ITMER).</p>

scholarly journals A Note on the Origin, Objectives and Programme of Project Merit

1980 ◽  
Vol 56 ◽  
pp. 275-276
Author(s):  
George A Wilkins
Keyword(s):  
International Collaboration ◽  
Working Group ◽  
International Association ◽  
General Assembly ◽  
International Council ◽  
Special Programme ◽  
The World ◽  
Draft Proposal ◽  
International Coordination ◽  
Set Up

Project MERIT is a special programme of international collaboration to Monitor Earth-Rotation and Intercompare the Techniques of observation and analysis. It was conceived in 1978 at IAU Symposium No 82 on Time and the Earth’s Rotation and a draft proposal was prepared by a working group set up by the Presidents of IAU Commissions 19 and 31. The proposal was endorsed at the IAU General Assembly at Montreal in 1979 August and at the IUGG General Assembly at Canberra in 1979 December, when the organisation and membership of the Working Group were modified accordingly. The Group is affiliated to the Commission on the International Coordination of Space Techniques for Geodesy and Geodynamics (CSTG), which is sponsored by the International Association of Geodesy (IAG) and by COSPAR. Project MERIT has received the support of the International Council of Scientific Unions and of many national organisations and observatories throughout the world.

scholarly journals On the eve of the 100th anniversary of IAU Commission 19/A2 “Rotation of the Earth”

2018 ◽  
Vol 13 (S349) ◽  
pp. 325-331
Author(s):  
Zinovy Malkin ◽  
Richard Gross ◽  
Dennis McCarthy ◽  
Aleksander Brzeziński ◽  
Nicole Capitaine ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Reference Frames ◽  
International Association ◽  
General Assembly ◽  
Reference Systems ◽  
Standing Committee ◽  
Earth Orientation ◽  
Terrestrial Reference Frames ◽  
The Earth ◽  
Rotation Of The Earth

AbstractIAU Commission 19 began in 1919 with the birth of the IAU at the Brussels Conference, where Standing Committee 19 on Latitude Variations was established as one of 32 standing committees. At the first IAU General Assembly in 1922, Standing Committee 19 became Commission 19 “Variation of Latitude”. In the beginning, the main topic of the Commission was the investigation of polar motion. Later, its activities included observations and theory of Earth rotation and connections between Earth orientation variations and geophysical phenomena. As a result, in 1964 at the XII IAU General Assembly, the Commission was renamed “Rotation of the Earth”. The investigation of Earth orientation variations is primarily based on observations of natural and artificial celestial objects. Therefore, maintenance of the international terrestrial and celestial reference frames, as well as the coordinate transformation between the frames and the improvement of the model of precession/nutation, have always been among the primary Commission topics. In 1987, the IAU through Commissions 19 and 31 “Time” established, jointly with the International Union of Geodesy and Geophysics, what is now known as the International Earth Rotation and Reference Systems Service. Commission 19 continued to work to develop methods to improve the accuracy and understanding of Earth orientation variations and related reference systems and frames as well as theoretical studies of Earth rotation. In 2015, Commission 19 was renewed as Commission A2 “Rotation of the Earth” continuing Commission 19’s functions and linking the astronomical community to other scientific organizations such as the International Association of Geodesy, International VLBI Service for Geodesy and Astrometry, International GNSS Service, International Laser Ranging Service and International DORIS Service. During its entire history, IAU Commission 19/A2 has always worked in close cooperation with these and other related services to improve the accuracy and consistency of the Earth orientation parameters and celestial and terrestrial reference frames.

16th and 17th Workshops of the International Association of Vegetation Science Working Group for the European Vegetation Survey (Rome, Italy, 22-26 March 2007; Brno, Czech Republic, 1-5 May 2008)

2008 ◽  
pp. 131-133
Author(s):  
T. M. Lysenko ◽  
Yu. A. Semenishchenkov
Keyword(s):  
Czech Republic ◽  
Working Group ◽  
International Association ◽  
Botanical Garden ◽  
European Countries ◽  
Vegetation Survey ◽  
Vegetation Science ◽  
The University ◽  
Science Working

22-26 March 2007 in Rome (Italy), in the Botanical garden of the University «La Sapienza» hosted the 16th meeting of the Working group «Review of the Vegetation of Europe» of the International Association of Vegetation Science (IAVS). These meetings are held every spring in one of the European countries and dedicated to various topics.

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