Patterns of atmospheric excitation functions of polar motion from high‐resolution regional sectors

2009 ◽  
Vol 114 (B4) ◽  
Author(s):  
J. Nastula ◽  
D. Salstein ◽  
B. Kolaczek
Keyword(s):  
High Resolution ◽  
Polar Motion ◽  
Excitation Functions ◽  
Atmospheric Excitation

scholarly journals Regional Signals in Atmospheric and Oceanic Excitation of Polar Motion

2000 ◽  
Vol 178 ◽  
pp. 463-472 ◽  
Author(s):  
Jolanta Nastula ◽  
Rui M. Ponte ◽  
David A. Salstein
Keyword(s):  
Atmospheric Pressure ◽  
Polar Motion ◽  
Ocean Model ◽  
Global Ocean ◽  
Relative Role ◽  
Bottom Pressure ◽  
Regional Patterns ◽  
Excitation Functions ◽  
Atmospheric Excitation ◽  
Environmental Prediction

AbstractAtmospheric and oceanic variability have been shown to play a role in the excitation of polar motion. Regional patterns of atmospheric and oceanic excitation are analysed and compared. The equatorial excitation functions, χ1 an χ2, for the ocean are computed using velocity and mass fields from a near-global ocean model, driven by observed surface winds stresses, surface heat and freshwater fluxes, for the period from January 1985 to June 1997. To understand the relative role of the ocean versus the atmosphere, we used atmospheric excitation functions computed from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalyses. We consider regional mass terms [bottom pressure and atmospheric surface pressure with the inverted barometer (IB) correction] and regional motion terms as well (currents and winds). Results here confirm recent findings that oceans supplement the atmosphere as an important source for polar motion excitation. Regional signals in the oceanic bottom pressure terms have comparable amplitudes to those in the atmospheric pressure-IB terms. The regional wind term amplitudes, however, are several times larger than the values for both regional oceanic currents term and atmospheric pressure-IB term. Power in regional oceanic excitation is distributed between seasonal and subseasonal timescales while in the case of atmospheric excitation it is concentrated rather at seasonal timescales.

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

1997 ◽  
Vol 15 (11) ◽  
pp. 1439-1446 ◽  
Author(s):  
J. Nastula ◽  
W. Kosek ◽  
B. Kolaczek
Keyword(s):  
Polar Motion ◽  
Correlation Coefficients ◽  
Analysis Data ◽  
Excitation Functions ◽  
Northern Latitudes ◽  
Atmospheric Excitation ◽  
Short Period ◽  
Amplitude Spectra ◽  
Period Variations ◽  
Polar Motion Excitation

Abstract. 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.

scholarly journals Short-Period Oscillations of Earth Rotation

2000 ◽  
Vol 178 ◽  
pp. 533-544 ◽  
Author(s):  
B. Kołaczek ◽  
W. Kosek ◽  
H. Schuh
Keyword(s):  
Seasonal Variations ◽  
Earth Rotation ◽  
Polar Motion ◽  
Correlation Coefficients ◽  
Data Sets ◽  
Annual Variations ◽  
Geodetic Vlbi ◽  
Atmospheric Excitation ◽  
Short Period ◽  
Seasonal Oscillations

AbstractSub-seasonal variations and especially sub-seasonal oscillations with periods of about 120, 60, 50, 40 days in polar motion and of about 120, 60–90, and 50 days in LOD are presented. Variations of amplitudes of these sub-seasonal oscillations of polar motion are shown. Maxima of these amplitudes are of the order of 2–4 mas. These oscillations are elliptical ones. The correlation coefficients between geodetic and atmospheric excitation functions in this range of the spectrum are variable and have annual variations. Maxima of correlation coefficients are of the order of 0.6–0.8.Modern geodetic VLBI experiments provide very accurate results in polar motion and UT1–UTC with a temporal resolution of 3–7 minutes. Several irregular, quasi-periodic variations were found. In many UT1–UTC data sets, oscillations with periods around 8 hours and between 5 and 7 hours can be seen.

Gamma-ray production in the 170Er(p,n)170Tm nuclear reaction

Open Physics ◽  
2010 ◽  
Vol 8 (4) ◽  
Author(s):  
Alexandru Mihailescu ◽  
Gheorghe Cata-Danil
Keyword(s):  
High Resolution ◽  
Energy Range ◽  
Nuclear Reaction ◽  
Gamma Rays ◽  
Compound Nucleus ◽  
Beam Energy ◽  
Gamma Ray ◽  
Excitation Functions ◽  
Γ Ray ◽  
First Time

AbstractFor the first time discrete gamma-rays following the nuclear reaction 170Er(p,n)170Tm with enriched target were measured with a high resolution GeHP spectrometer. Protons delivered by the Bucharest FN Tandem Van de Graaff accelerator bombarded a thin self-supporting film of enriched erbium. Measured γ-ray energies (Eγ), their relative intensities (Iγ) and corresponding excitation functions for the beam energy range 2.0–3.6 MeV are reported in the present work. The measured excitation functions were fairly well reproduced by compound nucleus calculations based on the Hauser-Feshbach formalism.

scholarly journals Polar motion of the triaxial nonrigid Earth and atmospheric excitation

2011 ◽  
Vol 14 (3) ◽  
pp. 223-229
Author(s):  
Wei Chen ◽  
Wenbin Shen
Keyword(s):  
Polar Motion ◽  
Atmospheric Excitation

High resolution studies of electron excitation VI. Resonance series in helium

1977 ◽  
Vol 352 (1670) ◽  
pp. 441-449 ◽  
Keyword(s):  
Angular Momentum ◽  
High Resolution ◽  
Elastic Scattering ◽  
General Scheme ◽  
Optical Excitation ◽  
Electron Excitation ◽  
Excitation Functions ◽  
High Angular Momentum ◽  
Shape Resonances

We discuss the classification of resonances observed in the optical excitation functions of helium and show that there are series of terms 1s ns 2 2 S and 1s ns n p 2 P. Two other resonances are identified as 1s 3p 2 2 D and possibly 1s 3p 2 2 S and may also be members of series. Strong features in the excitation functions of D states are identified as shape resonances in states of high angular momentum. We draw attention to a number of sharp and weak features which can be seen both in excitation studies and elastic scattering, but which do not fit into the general scheme.

scholarly journals The influence of Antarctic ice loss on polar motion: an assessment based on GRACE and multi-mission satellite altimetry

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Franziska Göttl ◽  
Andreas Groh ◽  
Michael Schmidt ◽  
Ludwig Schröder ◽  
Florian Seitz
Keyword(s):  
Gravity Field ◽  
Polar Motion ◽  
Satellite Altimetry ◽  
Motion Vector ◽  
Ice Sheet ◽  
Position Vector ◽  
Random Errors ◽  
Excitation Functions ◽  
Antarctic Ice Sheet ◽  
The Antarctic

AbstractIncreasing ice loss of the Antarctic Ice Sheet (AIS) due to global climate change affects the orientation of the Earth’s spin axis with respect to an Earth-fixed reference system (polar motion). Here the contribution of the decreasing AIS to the excitation of polar motion is quantified from precise time variable gravity field observations of the Gravity Recovery and Climate Experiment (GRACE) and from measurements of the changing ice sheet elevation from altimeter satellites. While the GRACE gravity field models need to be reduced by noise and leakage effects from neighboring subsystems, the ice volume changes observed by satellite altimetry have to be converted into ice mass changes. In this study we investigate how much individual gravimetry and altimetry solutions differ from each other. We show that due to combination of individual solutions systematic and random errors of the data processing can be reduced and the robustness of the geodetic derived AIS polar motion excitations can be increased. We investigate the interannual variability of the Antarctic polar motion excitation functions by means of piecewise linear trends. We find that the long-term behavior of the three ice sheet subregions: EAIS (East Antarctic Ice Sheet), WAIS (West Antarctic Ice Sheet) and APIS (Antarctic Peninsula Ice Sheet) is quite different. While APIS polar motion excitations show no significant interannual variations during the study period $$2003-2015$$ 2003 - 2015 , the trend of the WAIS and EAIS polar motion excitations increased in 2006 and again in 2009 while it started slightly to decline in 2013. AIS mass changes explain about $$45\%$$ 45 % of the observed magnitude of the polar motion vector (excluding glacial isosatic adjustment). They cause the pole position vector to drift along $$59^{\circ }$$ 59 ∘ East longitude with an amplitude of 2.7 mas/yr. Thus the contribution of the AIS has to be considered to close the budget of the geophysical excitation functions of polar motion.

High resolution studies of electron excitation - I. The 4S states of helium and the energy scale

1973 ◽  
Vol 334 (1596) ◽  
pp. 135-147 ◽  
Keyword(s):  
High Resolution ◽  
Systematic Error ◽  
Electron Excitation ◽  
Energy Scale ◽  
Excitation Functions ◽  
Standard Deviations ◽  
Electron Monochromator ◽  
S States ◽  
Prominent Peak

We describe an electron monochromator using hemispherical deflecting electrodes and its application to the measurement of electron excitation functions. We present excitation functions of the 4 1 S and 4 3 S states of helium for energies within about 1 V of threshold. We find a prominent peak in each function and determine its energy as 4 1 S 23.937 ± 0.007 ± 0.011 eV, 4 3 S 23.939 ± 0.007 ± 0.009 eV, where the first limits represent a systematic error and the second are standard deviations of several determinations.

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