Longitudinal Variation in the Thermospheric Superrotation: CHAMP Observation and TIE‐GCM Simulation

2021 ◽  
Vol 48 (18) ◽  
Author(s):  
Hui Wang ◽  
H. Lühr ◽  
K. D. Zhang
Keyword(s):  
Longitudinal Variation

scholarly journals Comparison of seasonal and longitudinal variation of daytime MSTID activity using GPS observation and GAIA simulations

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Mani Sivakandan ◽  
Yuichi Otsuka ◽  
Priyanka Ghosh ◽  
Hiroyuki Shinagawa ◽  
Atsuki Shinbori ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Meridional Wind ◽  
Lower Atmosphere ◽  
Electron Content ◽  
Longitudinal Variation ◽  
Total Electron ◽  
Winter Peak ◽  
Density Perturbations ◽  
Two Peaks ◽  
Gps Observations

AbstractThe total electron content (TEC) data derived from the GAIA (Ground-to-topside model of Atmosphere Ionosphere for Aeronomy) is used to study the seasonal and longitudinal variation of occurrence of medium-scale traveling ionospheric disturbances (MSTIDs) during daytime (09:00–15:00 LT) for the year 2011 at eight locations in northern and southern hemispheres, and the results are compared with ground-based Global Positioning System (GPS)-TEC. To derive TEC variations caused by MSTIDs from the GAIA (GPS) data, we obtained detrended TEC by subtracting 2-h (1-h) running average from the TEC, and calculated standard deviation of the detrended TEC in 2 h (1 h). MSTID activity was defined as a ratio of the standard deviation to the averaged TEC. Both GAIA simulation and GPS observations data show that daytime MSTID activities in the northern and southern hemisphere (NH and SH) are higher in winter than in other seasons. From the GAIA simulation, the amplitude of the meridional wind variations, which could be representative of gravity waves (GWs), shows two peaks in winter and summer. The winter peak in the amplitude of the meridional wind variations coincides with the winter peak of the daytime MSTIDs, indicating that the high GW activity is responsible for the high MSTID activity. On the other hand, the MSTID activity does not increase in summer. This is because the GWs in the thermosphere propagate poleward in summer, and equatorward in winter, and the equatorward-propagating GWs cause large plasma density perturbations compared to the poleward-propagating GWs. Longitudinal variation of daytime MSTID activity in winter is seen in both hemispheres. The MSTID activity during winter in the NH is higher over Japan than USA, and the MSTID activity during winter in the SH is the highest in South America. In a nutshell, GAIA can successfully reproduce the seasonal and longitudinal variation of the daytime MSTIDs. This study confirms that GWs cause the daytime MSTIDs in GAIA and amplitude and propagation direction of the GWs control the noted seasonal variation. GW activities in the middle and lower atmosphere cause the longitudinal variation.

Longitudinal variation in food sources and their use by aquatic fauna along a subtropical river in Taiwan

2012 ◽  
Vol 57 (9) ◽  
pp. 1839-1853 ◽  
Author(s):  
HAO-YEN CHANG ◽  
SHENG-HAI WU ◽  
KWANG-TSAO SHAO ◽  
WEN-YUAN KAO ◽  
CAN-JEN W. MAA ◽  
...  
Keyword(s):  
Food Sources ◽  
Longitudinal Variation ◽  
Aquatic Fauna

scholarly journals Local Mixing Events in the Upper Troposphere and Lower Stratosphere. Part I: Detection with the Lyapunov Diffusivity

2009 ◽  
Vol 66 (12) ◽  
pp. 3678-3694 ◽  
Author(s):  
Francesco d’Ovidio ◽  
Emily Shuckburgh ◽  
Bernard Legras
Keyword(s):  
Lyapunov Exponent ◽  
Lower Stratosphere ◽  
Effective Diffusivity ◽  
Strong Mixing ◽  
Longitudinal Variation ◽  
Western Atlantic ◽  
Upper Troposphere ◽  
Subtropical Jet ◽  
Active Mixing ◽  
The Western Pacific

Abstract A new diagnostic (the “Lyapunov diffusivity”) is presented that has the ability to quantify isentropic mixing in diffusion units and detects local mixing events by describing latitude–longitude variability. It is a hybrid diagnostic, combining the tracer-based effective diffusivity with the particle-based Lyapunov exponent calculation. Isentropic mixing on the 350-K surface shows that there is significant longitudinal variation to the strength of mixing at the northern subtropical jet, with a strong mixing barrier over Asia and the western Pacific, a weaker mixing barrier over the western Atlantic, and active mixing regions at the jet exits over the eastern Pacific and Atlantic.

scholarly journals Longitudinal variation in mechanical competence of bone along the avian humerus.

1995 ◽  
Vol 198 (1) ◽  
pp. 209-212
Author(s):  
R H Bonser
Keyword(s):  
Mechanical Properties ◽  
Trabecular Bone ◽  
Cortical Bone ◽  
Vickers Microhardness ◽  
Bird Species ◽  
Longitudinal Variation ◽  
The Mean ◽  
Compressive Tests

Vickers microhardness tests were used to gauge the mechanical "competence" (ability to resist bending and failure) of cortical and trabecular bone along the humeri of three bird species. Hardness was greatest at the mid-length portion of the shaft. The mean hardness of trabeculae, where present, was between 78.7 and 90.9% of that of the adjacent cortical bone. The possible causes of this are briefly discussed. Microhardness tests offer the opportunity to gauge differences in mechanical properties over small distances and might usefully be applied to test the homogeneity of mechanical properties within specimens for tensile or compressive tests.

Hemodynamic Measurements in Human Arterial Casts, and Their Correlation With Histology and Luminal Area

1980 ◽  
Vol 102 (3) ◽  
pp. 247-251 ◽  
Author(s):  
M. H. Friedman ◽  
C. B. Bargeron ◽  
G. M. Hutchins ◽  
F. F. Mark ◽  
O. J. Deters
Keyword(s):  
Laser Doppler Anemometer ◽  
Longitudinal Variation ◽  
Sectional Area ◽  
Vascular Response ◽  
Velocity Measurements ◽  
Cross Sectional ◽  
New Approach ◽  
Flow Acceleration ◽  
Luminal Area ◽  
Hemodynamic Measurements

A new approach is presented for studying the vascular response to hemodynamic stress. A laser doppler anemometer is used to make velocity measurements very near the walls of human arterial casts; these measurements are then correlated with the histology of the artery from which the cast was made. Several illustrative results are given which suggest that the velocity profiles along the outer walls of aortic bifurcations may be significantly determined by the longitudinal variation of cross-sectional area. The shapes of these profiles were qualitatively different for each cast studied. In one specimen, the location of initial lipid deposits appeared to correlate with flow acceleration.

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