On the kinetic energy of the divergent and nondivergent flow in the atmosphere

Abstract

The kinetic rncrgy of horizontal flow in a hydrostatic atmosphere is divided into the kinctir cnxgies of its divergent and nondivergent components. The law of conversion betwoen these two cnergics for large-scale flows in the atmosphere is derived and discussed using balancrtl and unbalanced models of circulations in the atmosphere. It is shown that the total potential energy is converted into the kinetic energy of the divergent flow which, in turn, is convrrted into the kinetic energy of the nondivergent flow. These energy conversions are equal in a so-called balanced model, but may differ in a model based on tho primitivr? equations. The analysis shows that the kinetic enrrgy reservoir of the divergent part of the flow may play a quasi-catalytic role in tha energy ronversion betwwn the total potential energy and the kinetic energy of tho nondivergent flow. Two sets of data, the history data generated by the NCAR GCM of January simulation, and tho NMC wind data and FNWC height field of August 1 to 15 of 1970, wcrc used to evaluate the energies and energy conversions. The computations confirm the direction of energy conversions in the theoretical argurncnt ant1 the quasi-catalytic nature of the kinetic energy of the divergent part of the flow. The energy conversions hctween the total potential energy and the kinetic energy of tho divergent flow occurs mainly in the lower layers of the rttmosphero a t middle latitutics where the baroclinic eddy activities are dominant. The energy conversion between the kinrtic cnergies of the divergent and the nondivergent flows is mostly carried out by t,hc Coriolis effect. In other words, the quasi-geostrophic model explains most of this energy conversion. The introduction of n more sophisticated model gives small improvement as far as t h r magnitude of energy is concerned. 5 Present affiliation: European Center for Medium Range Weather Forecasts, Bracknell, Berkshire,

A Study of the Kinetic Energy Generation with General Circulation Models

“…Note that the integration of -* over the entire hemisphere is approximately equal to C(A, K)=1/gS *s *p0 0 (-*)dSdp, the conversion from available potential energy (A) to kinetic energy (K). Table 2 displayed C(A, K) computed by Chen et al (1981) for the -1978winter and Chen (1982 for the 1976-1977 winter. The contrast between Tables 1 and 2 shows that -[V*] computed in the current study is comparable to C(A, K) of previous studies.…”

Kinetic Energy Budget of a Tropical Cyclone

“…with the generation of kinetic energy due to barotropic and baroclinic processes, respectively [27] [38]. The barotropic term integrates to zero in a closed domain [27], but not in an open domain as considered here.…”

“…The barotropic term integrates to zero in a closed domain [27], but not in an open domain as considered here. Using (5) and (6), we can rewrite (1) as …”

“…Using summertime data of Northern Hemispheric, the ratio of divergent kinetic energy to the total amount is approximately 0.10 to be found [27]. In other words, the dominant component of 200 hPa tropical flow is the rotational wind [28]- [33].…”

“…In their global study, [27] showed that the kinetic energy of the divergent wind K D is very small compared to that of the nondivergent wind K R . However, [45] noted that K D may be significant in severe storms.…”