Advances in Research on Atmospheric Energy Propagation and the Interactions between Different Latitudes

Early theoretical analyses indicated that the tropics and extratropics are relatively independent due to the existence of critical latitudes.However,considerable observational evidence has shown that a clear dynamical link exists between the tropics and midlatitudes.To better understand such atmospheric teleconnection,several theories of wave energy propagation are reviewed in this paper：（1） great circle theory,which reveals the characteristics of Rossby waves propagating in the spherical atmosphere;（2） westerly duct theory,which suggests a ＂corridor＂ through which the midlatitude disturbances in one hemisphere can propagate into the other hemisphere;（3） energy accumulation-wave emanation theory,which proposes processes through which tropical disturbances can affect the atmospheric motion in higher latitudes;（4） equatorial wave expansion theory,which further explains the physical mechanisms involved in the interaction between the tropics and extratropics;and（5） meridional basic flow theory,which argues that stationary waves can propagate across the tropical easterlies under certain conditions.In addition,the progress made in diagnosing wave-flow interaction,particularly for Rossby waves,inertial-gravity waves,and Kelvin waves,is also reviewed.The meridional propagation of atmospheric energy exhibits significant annual and interannual variations,closely related to ENSO and variation in the westerly jets and tropical upper-tropospheric troughs,amongst others.

A survey of instantaneous poles for a class of two-degree-of- freedom spherical mechanisms

This paper is a detailed exploration of instantaneous poles for a class of two-degree-of-freedom （two-DOF） spherical mechanisms （SMs） with seven links or bars. For two-DOF SMs, the secondary instantaneous poles （the ones which cannot be found by direct inspection） must lie on the specified great circles. For many of these mechanisms, however, some of these great circles cannot be obtained by a direct application of Aronhold-Kennedy theorem. This paper presents geome- trical and analytical techniques to locate these unknown great circles for three topologies of seven-bar two-DOF SMs.

On the location of the secondary instantaneous poles in two-degree-of-freedom spherical mechanisms

As the instant centers in planar mechanisms, the instantaneous poles （or instant poles, in brief） can be used for kinematic analysis in spherical mechanisms. One of the mandatory steps in this analysis is the determination of the location of these poles. This paper presents a theorem showing analytically that the locus of an unknown secondary instant pole in two-degree-of-freedom （2-DOF） spherical mechanisms is a great circle （GC）. The exact location of the pole on its GC is obtained based on the configuration of the mechanism and velocity ratio of the two inputs. Moreover, using the results of the theorem, a geometrical technique is presented to determine the GC of the pole.

A STUDY ON DEFORMATIONS OF RAY AND ITS RELEVANT FACTORS

In this paper,the effects of first and second meridional derivative(i.e.h_s~,d^2f/dy^2,″)of the Coriolis parameter,Westerly profile and topography structure on ray routes are qualitatively analysed by use of a sim- plified mathematical model.The analysis indicates that the second derivatives of the above relevant factors play an important role in the formation of great circle route.A profile of west wind similar to the real atmosphere may result in a“sine wave pattern”of ray.The effects of west wind shear,β factor and the slope of topography on the scale of radius of great circle,critical latitude of rays ard the amplitude of wave train of teleconnection aro also discussed.Additionally,the characters of critical velocity profile for meridionally trapped wave are men- tioned.