scholarly journals Main Results of Studying the Nature of the Irregularity of the Earth's Rotation

1979 ◽  
Vol 82 ◽  
pp. 61-64 ◽  
Author(s):  
N. S. Sidorenkov
Keyword(s):  
Angular Momentum ◽  
Cross Sections ◽  
Zonal Wind ◽  
Atmospheric Angular Momentum ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Relative Angular Momentum ◽  
Northern And Southern Hemispheres

The variations of the atmospheric angular momentum were investigated (Sidorenkov, 1976). Using the climatic cross-sections of the zonal wind, the values of the relative angular momentum of the atmosphere, h, were calculated for each month. The variations of h during the year are shown in Figure 1, where curve 1 illustrates the sum of h for the entire atmosphere, and curves 2 and 3 illustrate h for the atmospheres of the northern and southern hemispheres respectively.

Irregularities in the Earth’s rotation and the prognosis for the global component of the atmospheric angular momentum

2010 ◽  
Vol 55 (5) ◽  
pp. 217-222
Author(s):  
L. D. Akulenko ◽  
Yu. G. Markov ◽  
V. V. Perepelkin ◽  
I. V. Skorobogatykh
Keyword(s):  
Angular Momentum ◽  
Atmospheric Angular Momentum ◽  
Earth’S Rotation ◽  
Earth's Rotation

Addendum 2020 to ‘Measurement of the Earth’s rotation: 720 BC to AD 2015’

2021 ◽  
Vol 477 (2246) ◽  
pp. 20200776
Author(s):  
L. V. Morrison ◽  
F. R. Stephenson ◽  
C. Y. Hohenkerk ◽  
M. Zawilski
Keyword(s):  
Angular Momentum ◽  
Earth’S Rotation ◽  
The Sun ◽  
Earth's Rotation ◽  
Moon System ◽  
Link Type ◽  
The Earth ◽  
Solar Eclipses ◽  
Rotation Of The Earth

Historical reports of solar eclipses are added to our previous dataset (Stephenson et al. 2016 Proc. R. Soc. A 472 , 20160404 ( doi:10.1098/rspa.2016.0404 )) in order to refine our determination of centennial and longer-term changes since 720 BC in the rate of rotation of the Earth. The revised observed deceleration is −4.59 ± 0.08 × 10 −22  rad s −2 . By comparison the predicted tidal deceleration based on the conservation of angular momentum in the Sun–Earth–Moon system is −6.39 ± 0.03 × 10 −22  rad s −2 . These signify a mean accelerative component of +1.8 ± 0.1 × 10 −22  rad s −2 . There is also evidence of an oscillatory variation in the rate with a period of about 14 centuries.

Flows in a rotating spherical shell: the equatorial case

1994 ◽  
Vol 276 ◽  
pp. 233-260 ◽  
Author(s):  
A. Colin de Verdière ◽  
R. Schopp
Keyword(s):  
Angular Momentum ◽  
Rotation Axis ◽  
Dynamic Pressure ◽  
Vertical Component ◽  
Low Frequency ◽  
Zonal Flow ◽  
Horizontal Component ◽  
Meridional Plane ◽  
Earth’S Rotation ◽  
Earth's Rotation

It is well known that the widely used powerful geostrophic equations that single out the vertical component of the Earth's rotation cease to be valid near the equator. Through a vorticity and an angular momentum analysis on the sphere, we show that if the flow varies on a horizontal scale L smaller than (Ha)1/2 (where H is a vertical scale of motion and a the Earth's radius), then equatorial dynamics must include the effect of the horizontal component of the Earth's rotation. In equatorial regions, where the horizontal plane aligns with the Earth's rotation axis, latitudinal variations of planetary angular momentum over such scales become small and approach the magnitude of its radial variations proscribing, therefore, vertical displacements to be freed from rotational constraints. When the zonal flow is strong compared to the meridional one, we show that the zonal component of the vorticity equation becomes (2Ω.Δ)u1 = g/ρ0)(∂ρ/a∂θ). This equation, where θ is latitude, expresses a balance between the buoyancy torque and the twisting of the full Earth's vorticity by the zonal flow u1. This generalization of the mid-latitude thermal wind relation to the equatorial case shows that u1 may be obtained up to a constant by integrating the ‘observed’ density field along the Earth's rotation axis and not along gravity as in common mid-latitude practice. The simplicity of this result valid in the finite-amplitude regime is not shared however by the other velocity components.Vorticity and momentum equations appropriate to low frequency and predominantly zonal flows are given on the equatorial β-plane. These equatorial results and the mid-latitude geostrophic approximation are shown to stem from an exact generalized relation that relates the variation of dynamic pressure along absolute vortex lines to the buoyancy field. The usual hydrostatic equation follows when the aspect ratio δ = H/L is such that tan θ/δ is much larger than one. Within a boundary-layer region of width (Ha)1/2 and centred at the equator, the analysis shows that the usually neglected Coriolis terms associated with the horizontal component of the Earth's rotation must be kept.Finally, some solutions of zonally homogeneous steady equatorial inertial jets are presented in which the Earth's vorticity is easily turned upside down by the shear flow and the correct angular momentum ‘Ωr2cos2(θ)+u1rCos(θ)’ contour lines close in the vertical–meridional plane.

Irregularities in the Earth’s rotation and the overall angular momentum of the atmosphere

2010 ◽  
Vol 54 (3) ◽  
pp. 260-268 ◽  
Author(s):  
L. D. Akulenko ◽  
Yu. G. Markov ◽  
V. V. Perepelkin ◽  
L. V. Rykhlova
Keyword(s):  
Angular Momentum ◽  
Earth’S Rotation ◽  
Earth's Rotation

scholarly journals Connection between the length of day and wind measurements in the mesosphere and lower thermosphere at mid- and high latitudes

2019 ◽  
Vol 37 (1) ◽  
pp. 1-14
Author(s):  
Sven Wilhelm ◽  
Gunter Stober ◽  
Vivien Matthias ◽  
Christoph Jacobi ◽  
Damian J. Murphy
Keyword(s):  
Solar Radiation ◽  
Zonal Wind ◽  
Large Scale ◽  
Lower Thermosphere ◽  
Earth’S Rotation ◽  
The Sun ◽  
Earth's Rotation ◽  
The Earth ◽  
The Mean ◽  
Mesosphere And Lower Thermosphere

Abstract. This work presents a connection between the density variation within the mesosphere and lower thermosphere (MLT) and changes in the intensity of solar radiation. On a seasonal timescale, these changes take place due to the revolution of the Earth around the Sun. While the Earth, during the northern-hemispheric (NH) winter, is closer to the Sun, the upper mesosphere expands due to an increased radiation intensity, which results in changes in density at these heights. These density variations, i.e., a vertical redistribution of atmospheric mass, have an effect on the rotation rate of Earth's upper atmosphere owing to angular momentum conservation. In order to test this effect, we applied a theoretical model, which shows a decrease in the atmospheric rotation speed of about ∼4 m s−1 at a latitude of 45∘ in the case of a density change of 1 % between 70 and 100 km. To support this statement, we compare the wind variability obtained from meteor radar (MR) and Microwave Limb Sounder (MLS) satellite observations with fluctuations in the length of a day (LOD). Changes in the LOD on timescales of a year and less are primarily driven by tropospheric large-scale geophysical processes and their impact on the Earth's rotation. A global increase in lower-atmospheric eastward-directed winds leads, due to friction with the Earth's surface, to an acceleration of the Earth's rotation by up to a few milliseconds per rotation. The LOD shows an increase during northern winter and decreases during summer, which corresponds to changes in the MLT density due to the Earth–Sun movement. Within the MLT the mean zonal wind shows similar fluctuations to the LOD on annual scales as well as longer time series, which are connected to the seasonal wind regime as well as to density changes excited by variations in the solar radiation. A direct correlation between the local measured winds and the LOD on shorter timescales cannot clearly be identified, due to stronger influences of other natural oscillations on the wind. Further, we show that, even after removing the seasonal and 11-year solar cycle variations, the mean zonal wind and the LOD are connected by analyzing long-term tendencies for the years 2005–2016.

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