## Ed

which holds for t»tm.

Let us compare periods of establishing UML and DL. The first, as was found above, is equal to tm = (a + 1 a 2.3 years, and the second is td = s~ 1(a~1 + /P1) a 94 years. Hence, the time required to establish the equilibrium state of UML is about 2.4% of DL.

Let us match asymptotic solutions (1.1.16) and (1.1.19), that is, we sum them and subtract the general term. As a result we obtain

Equations (1.1.18) and (1.1.20) represent the solution of (1.1.1)-(1.1.4).

We have deduced that the time to establish the equilibrium state of separate subsystems of the atmosphere-UML-DL system is governed by the inequality ia « tm « td. One can judge the time for setting-in of other subsystems of the climatic system from estimates of the characteristic time for vertical heat diffusion. The latter, together with the geometric and thermophysical parameters of separate subsystems, is presented in Table 1.1. As can be seen, if the characteristic time for vertical heat diffusion is taken as a measure of the relaxation time, then even on time scales of the order of 106 s the atmosphere, UML, sea ice, snow cover and active layer of land must be combined in a single climatic system.

Using the terminology of thermodynamics we introduce the concepts of open, closed and isolated systems. A system which exchanges its matter with the environment will be called an open system; a system which does not exchange its matter with the environment will be called a closed system and a system which does not interact with the environment, that is, does not exchange either energy or matter, will be called an isolated system. Thus, in terms of thermodynamics the climatic system represents a non-isolated system consisting of macroscopic subsystems, each of which has an extremely large number of degrees of freedom and interacts with every other and with the environment.

Observational data demonstrate a great diversity of climatic system oscillations. According to Monin (1969), the majority of these fall into one of the following categories:

1. Small-scale oscillations, with periods ranging from fractions of a second up to several minutes, governed by turbulence and wave processes of different kinds (such as acoustic and gravitational waves in the atmosphere).

2. Mesoscale oscillations, with periods ranging from several minutes to several hours (in particular, inertial oscillations belong to this group). Their intensity is relatively small and, therefore, the energy spectrum in the indicated time range contains wide and deep minima, separating quasi-horizontal synoptic disturbances from three-dimensional small-scale heterogeneities.

3. Synoptic oscillations, with periods ranging from several hours up to several days

Let us match asymptotic solutions (1.1.16) and (1.1.19), that is, we sum them and subtract the general term. As a result we obtain

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