排序方式： 共有21条查询结果，搜索用时 31 毫秒
1.
Available potential energy in the atmosphere 总被引：2，自引：0，他引：2
Y. L. McHall 《Meteorology and Atmospheric Physics》1990,42(1):39-55
Summary The study of available potential energy is approached in a new way. According to the second law of thermodynamics, we may find, from among the states which can be attained through all the actual processes in an isolated atmosphere, the limit state, referred to as the lowest state, that is achieved by means of reversible processes and possesses the least total potential energy. Thus, the maximum available potential energy can be estimated by taking the lowest state as the reference state. The variations of the lowest state and maximum available potential energy with baroclinity and mean static stability are illustrated graphically as some examples in the text. This study gives a more fundamental understanding for the kinetic energy generation in the baroclinic atmosphere. Also, the extreme kinetic generation in irreversible processes is investigated. The obtained results may be adopted for the energetics of explosive systems in the atmosphere.With 10 Figures 相似文献
2.
Yong. L. McHall 《大气科学进展》1991,8(2):225-236
The contribution of thermal forcing to the planetary stationary waves will be studied also by assuming that heat balance in stationary waves over zonally asymmetric thermal forcing must be maintained over a long time period. Us-ing the same model of geostrophic waves introduced in Part I, we may explain successfully the observed and simulated responses to the thermal forcing in the atmosphere, such as the wave 1 structure at high levels of middle latitudes, the seasonal changes of the stationary waves in the Northern Hemisphere, the opposite phase distributions of stationary waves at high and low levels of the subtropical regions in both hemispheres and so on. 相似文献
3.
Yong. L. McHall 《大气科学进展》1991,8(3):327-338
The zonal momentum generation in forced stationary waves may exceed the requirement for momentum balance after long, if the waves do not change their patterns, This suggests that the changes in stationary wave patterns would be required by maintenance of momentum balance over the external forcings. It will be found that the low frequency anomalies like blocking regimes may produce reversed zonal momentum variations, if they happen in the observed centre areas. The zonal momentum balance in the stationary waves may be maintained effectively by alternation between the normal and blocking circulation regimes, Thus, from the point of long-term zonal momentum balance, we may explain the geographical distributions of the blocking centres and the seasonal variations in blocking areas and frequencies. 相似文献
4.
Advances in Atmospheric Sciences - 相似文献
5.
Yong L. McHall 《大气科学进展》1993,10(4):393-406
The group velocity used in meteorology in the last 30 years was derived in terms of conservation of wave energy or crests in wave propagation. The conservation principle is a necessary but not a sufficient condition for deriving the mathematical form of group velocity, because it cannot specify a unique direction in which wave energy or crests propagate. The derived mathematical expression is available only for isotropic waves. But for anisotropic waves, the traditional group velocity may have no a definite direction, because it varies with rotation of coordinates. For these reasons, it cannot be considered as a general expression of group velocity. A ray defined by using this group velocity may not be the trajectory of a reference point in an anisotropic wave train. The more general and precise expression of group velocity which is applicable for both isotropic and anisotropic waves and is independent of coordinates will be derived following the displacement of not only a wave envelope phase but also a wave reference point on the phase. 相似文献
6.
Yong. L. McHall 《大气科学进展》1992,9(2):173-190
The instability of geostrophic wave circulations related to the nonlinear processes involved in the zonal mean heat balance equations is studied. It is found that the planetary waves may be destabilized by thermal forcing in spe-cific baroclinic layers, called the breaking layers. The critical conditions of the instability will be given. In the troposphere, these conditions may be provided in blocking regions and the development of planetary perturbations is characterized distinctly by the unset, maintenance and decay of observed blocks. The whole blocking episode cannot be described as either the barotropic or baroclinic process only. The limitations on the study of wave-wave interaction using spectral models or spectrum analyses will be discussed also. 相似文献
7.
Y. L. McHall 《大气科学进展》1992,9(3):299-310
The stratospheric worm pools, called the 4-day wave also, are mainly the temperature anomalies in the polar re-gions of winter hemisphere. It will be shown that their occurrence, propagation speed and specific structure can be explained by the lower frequency coherent heating resulting from the wave interaction in the breaking layers of the stratosphere. Although their vertical phase slope is negligibly small, the warm pools cannot be considered as a barotropic anomaly. 相似文献
8.
Y.L. McHall 《大气科学进展》1993,10(3):273-286
In development of baroclinic disturbances, baroclinity of basic temperature field varies with conversion of available potential energy. The growth rate which depends on the baroclinity varies as well. However, in previous linear theories, the growth rate was considered constant, so development of disturbances was not constrained by energy sources in the linear theories. In terms of energy conservation and conversion in an isolated atmosphere, we may study the variations in the baroclinity and growth rate and draw the corresponding pictures of perturbation developments in the varying environments. The amplification for the most unstable Eady wave is discussed as an example. It will be found that growth of baroclinic perturbations constrained by energy conservation is significantly different from the growth at the initial constant rate after mature stage. 相似文献
9.
Yong. L. McHall 《大气科学进展》1990,7(4):395-408
The kinetic energy generation in either the dry or moist atmosphere may be estimated by the same relationships if we introduce the new concept of generalized available potential energy. The largest magnitude of generalized availa-ble potential energy and corresponding reference state of either dry or moist atmosphere are calculated in terms of the initial conditions and entropy variation of the atmosphere. The obtained relationships are applicable for the statically unstable atmosphere as well. The generalized available potential energy associated with reversible processes reaches the maximum with respect to same initial state. While the generation of kinetic energy in irreversible processes is characterized by sudden changes. When the reference state is assumed to be saturated, we may predict the final tem-perature and moisture fields corresponding to provided initial state and entropy variation. 相似文献
10.
Yong L.McHall 《大气科学进展》1993,(4)
It has been argued in Part I that traditional expression of multidimensional group velocity used in meteorology is only applicable for isotropic waves. While for anisotropic waves, it cannot manifest propagation of waves group along the trajectory of a reference wave point, and varies with rotation of coordinates. The general mathematical expression of group velocity which may be used also for anisotropic waves has been derived in Part I. It will be proved that the mean wave energy, momentum and wave action density are all conserved as a wave group propagates at the general group velocity. Since general group velocity represents the movement of a reference point in either isotropic or anisotropic wave trains, it may be used to define wave rays. The variations of wave parameters along the rays in a slowly varying environment are represented by ray-tracing equations. Using the general group velocity, we may derive the anisotropic ray-tracing equations, which give the traditional ray-tracing equations for 相似文献