Bibliography

A. Kh. Khrgian, Atmospheric Physics, Gostekhizdat, Moscow, 1953, 456 pp., 220 figs.

Soviet meteorology is developing rapidly both in the areas of experiment, observation, and theory, and in the area of practical applications. As a result, original monographs have appeared on climatology, dynamic meteorology, the physics of the near-surface layer, and general meteorology. We now read Professor A. Kh. Khrgian’s Atmospheric Physics.

The content of this book is many-sided and varied. It contains 22 chapters, in which questions of the composition and structure of the atmosphere are discussed, including the properties of its high layers, atmospheric dynamics and thermodynamics, radiation processes, turbulence, the physics of clouds and precipitation, the fundamentals of weather forecasting, general atmospheric circulation, and a number of other topics. The book does not touch upon such branches of atmospheric physics as atmospheric electricity, atmospheric optics, and acoustics. Such a limitation may be regarded as appropriate, since sufficiently complete modern courses and manuals exist for these branches.

In almost all sections of the book modern material is brought in. Thus, for example, in the chapter on the composition of the atmosphere (which in previous textbooks was always very brief), modern views are set forth on the role of the processes of gas separation, their escape from the atmosphere, on atomic and molecular processes and the phenomena of absorption and emission of energy that influence the state of gases in the atmosphere. For the first time in a textbook, data appear on atmospheric sodium, on hydrogen and hydroxyl in the atmosphere, as well as later, for example, data on cellular circulation and the clouds associated with it, on the structure of cold katafronts and anafronts, on the seasonal change of winds at altitudes above 15–18 km, and so forth. The book discusses the Soviet scientific studies carried out on the composition of the atmosphere, atmospheric dust, solar and terrestrial radiation, and especially on the processes of evaporation and condensation of water vapor, the formation of clouds and precipitation. The work done in the USSR devoted to methods of artificial influence on the climate and its elements—on air temperature (§ 57), air humidity (§ 86), and the structure of turbulence (§ 118)—is described in considerable detail. On a number of questions the author restores the priority of domestic science, as, for example, in the question of interpreting the causes of the infrared glow of the night sky (§ 7), the study of the microstructure of clouds (§ 92), of “involvement” of air in ascending currents (§ 96), of the application of the equations of motion of a body of variable mass (first given by Meshchersky) to a number of atmospheric phenomena (§§ 96, 110), of the theory of lee air waves (§ 150), and so on.

It is to be welcomed that the author has endeavored to give a brief mathematical theory of the most important atmospheric phenomena, based on simple physical premises, indicating to what extent this theory correctly describes the observed details of the phenomena. Thus, for example, the author notes that the existing theory of mountain-valley winds correctly describes the motion in the lower layers and does not explain the presence of a strong upper return current (p. 404). In exactly the same way, the author successfully connects the main conclusions of the theory of evaporation with the existing empirical formulas for calculating evaporation (pp. 225–230), and so forth. Experimental data also allow the author to criticize certain conclusions of foreign researchers who had undeservedly enjoyed earlier recognition—for example, Finzeisen’s hypothesis on the nuclei of sublimation (p. 247). The author correctly avoids presenting large tables of experimental data, always limiting himself only to brief numerical data.

In a number of sections the author reflects the results of his own personal investigations or collective works in which he took part; the corresponding passages seem to us to be the most vividly presented.

On the whole, the book is characterized by brevity of exposition and the ability to single out what is most essential, which is valuable for a textbook. True, this is sometimes connected with the absence of intermediate derivations, which may hinder the beginning reader.

Below we shall consider the contents of the book by chapters and make separate remarks.

The “Introduction” treats the subject of atmospheric physics and its tasks quite fully. In the first three chapters a very complete description is given of the structure of the atmosphere, and the question of ozone and atmospheric dust is considered. § 17 (ch. III) calls for comment. Here, for the example of “large and small dust particles,” the author adduces the well-known theory of exchange—a theory that is correct only for substances passively transported by the air. The reservation at the end of the paragraph that the vertical velocity of the dust particles must be taken into account does not alter the matter, for if it is taken into account, then essentially the entire theory must be reworked. In doing so it should be borne in mind that the vertical motions of dust particles, as is known, depend not only on the force of gravity but also on their heating by the sun or cooling by radiation (Voeikov effect).

Chapter IV is devoted to water vapor. In it we do not find a description of the diurnal variation of absolute and relative humidity and of the distribution of these elements with height in the surface layer. The latter question is not reflected in the book at all, and the diurnal variation of humidity is discussed in the chapter devoted to evaporation. This is hardly successful, because readers interested in the diurnal variation of water vapor, using the table of contents, will naturally turn to § 22 (ch. IV), entitled “Distribution of humidity in the surface layer.”

Information on the statics of the atmosphere (ch. V) and on adiabatic processes (ch. VI) is presented briefly, but is quite sufficient for a general acquaintance. In chapters VII and VIII, devoted to radiation processes, the fundamentals of the subject are also set forth rather briefly. Many new data are presented (§§ 48–53: reduced absorptivity of individual types of the earth’s surface, results of observations of radiation, the radiation balance of the desert, etc.). However, chapters VII–VIII are not free of certain inaccuracies. Doubt is raised by the reference to the fact that the surface layer of the atmosphere only 85 cm thick, with a water-vapor elasticity of 10–15 mb, absorbs 3.5–6% of all radiation from the earth at a temperature of 18° (p. 135). In our observations under the conditions of Central Asia, such a noticeable attenuation was not detected. On p. 136 an incorrect esti—

to differences in the effective radiation of the earth’s surface and of a black body at a level of 1–1.5 m, which is measured by the air temperature. The author considers these differences small. In fact, however, they may amount to more than 25% of the measured quantity. On p. 137 the author gives a completely incomprehensible and unfounded explanation of the causes of the nighttime decrease in the effective radiation of the earth. Here it should simply have been said that the radiation of the earth during the night decreases more rapidly than the radiation of the atmosphere.

On p. 138 the author states that “in the daytime, as we see, the effective radiation increases together with the increase of the temperature gradient in the lower layers of the atmosphere.” In the appended Tables 45 and 46, however, there are no data whatever on temperature gradients. In reality, the principal cause of the increase in effective radiation during the daytime is the heating of the soil surface and the associated increase in the radiation of the active surface. It would have been desirable to expand the discussion of the question of the radiation balance of the active surface, to give data on the radiation balance of various surfaces—field, water surface, snow cover, etc.—and to characterize seasonal changes in the balance, the time at which the balance passes through zero, and so on.

Chapter IX, on heat exchange in the upper layers of the soil and of water, raises no objections as to the material presented. However, neither here nor in other chapters of the book is the important question of the heat balance of the active surface considered; without it one cannot understand the basic features of the meteorological regime of the ground layer of air. In the only place in the book (p. 196, § 70), the heat-balance equation is used as one of the boundary conditions necessary for solving the problem of the diurnal course of temperature. At the same time the author does not dwell on the physical essence of the heat-balance equation. A separate paragraph should have been devoted to the heat balance. The book also does not illuminate the question of turbulent heat exchange between the active surface and the air.

Chapter X, “Distribution of Temperatures in the Lower Layers of the Atmosphere,” raises no objections. Here new data on the course of temperature in mountains and deserts are used; the dependence of temperature on the character of the underlying surface, the influence of vegetation, and so forth are described. The chapter concludes with a paragraph on frosts, in which the modern solution of the problem according to Lyutershtein—Chudnovsky is presented.

In the following chapter, XI, the author successfully combines an exposition of methods of theoretical calculation of the diurnal course of temperature with factual material (very illustrative graphs) indicating good agreement between calculated and actual data. Also of interest are the materials presented on the times of occurrence of the diurnal maximum and minimum of temperature (p. 198). Paragraph 71 (p. 199) begins with the assertion that “in the very lowest layer of air, 1.5–2 m thick, the temperature is to a large extent determined by the radiation conditions of the underlying surface and the atmosphere.” The same thought is repeated on the following page. This is not quite so. In this case the main role in the daytime is played not by radiation but by turbulent heat exchange between the active surface and the atmosphere.

The book gives no attention to the structural characteristics of temperature, nor to air humidity. Many interesting features in the micro-oscillations of temperature and humidity, with which our ideas about the character and dimensions of vortices in the atmosphere are connected, remain unilluminated.

The chapter on the temperature of the upper layers of the atmosphere is constructed entirely on new material that has not previously been used in the scholarly literature. The chapter on evaporation is presented with due regard to the latest ideas on the mecha-

in the mechanism of the evaporation process under natural conditions and contains the results of observations of evaporation from various surfaces.

The following four chapters (XIV—XVII) are devoted to topical questions that are now being intensively developed: condensation of water in the atmosphere, the physics of clouds and precipitation. The material here is fresh and new, a large part of it being published in textbook literature for the first time. This section of the book is read with great interest, because it synthesizes a broad complex of excellently performed domestic investigations. Here we also see new original photographs of clouds, structural photographs of cloud elements, and spectra of the sizes of cloud droplets. Theories used for calculating coagulation, etc., are also presented. Let us note here that on p. 239, in the discussion of the question of the dew point, the essential difference between the condensation temperature, the wet-bulb temperature, and the dew point is not explained. The very definition of the dew point (“the temperature at which the water vapor present in the air would be saturated with respect to the surface of water”) is unsatisfactory, since it says nothing about the method of cooling. The dew point is reached, as is known, under isobaric cooling; the condensation point under adiabatic cooling; the wet-bulb temperature under cooling by evaporation. Different processes determine different temperature values at the moment of saturation.

In the author’s formula (93.1) the value of the constant is given according to Borovikov, but the constant “\(c\)” has been forgotten. Even the order of its magnitude is not indicated. On p. 251 the text compares the content of water vapor in cloud droplets of liquid water and water vapor, but in Tables 89—90 the latter quantity is absent. No comparison can be made. The definition of high-layer clouds on p. 258, where it is said that this is a “thin veil of a grayish or bluish shade,” does not seem successful to us. These clouds not infrequently constitute a thick layer. In discussing the question of convective clouds, nothing is said about the so-called “penetrating convection.” At the beginning of Chapter XVI it would have been necessary at once to emphasize the difference between cloud and rain drops, consisting in the fact that cloud droplets have an average size of 10—20 microns, while precipitation drops have 100—200 microns, and that one must study the processes determining the growth of small droplets and their transformation into large ones. It is wrongly stated, for example (p. 303), that the distinction between continuous, shower, and drizzling precipitation belongs only to synoptic meteorology. This fundamental distinction is used in all branches of meteorology. Very little is said about aircraft icing, whereas considerably more attention and space ought to have been devoted to this important question. One must also regret the small number of cloud photographs.

Let us note the positive fact that Chapter XVIII gives an exposition of the theory of turbulence of Kolmogorov and Obukhov. However, the question of using the continuity equation to calculate vertical currents deserves more detailed treatment. Speaking of convergence and divergence, one should have mentioned Michel’s principle and its application at the present stage.

There are errors in Chapter XIX. In Fig. 161 a curvilinear isobar is drawn, while the caption reads: “forces acting in rectilinear motion (rectilinear isobars),” and in Fig. 162 the direction of the centrifugal force is incorrectly indicated. The author acted correctly in placing in § 128 (on the general equations of motion) the equations in Gromeko’s form; however, later, in presenting the problem of pressure changes, he did not use these equations, limiting himself only to a brief exposition of the first approximation of Kibbel’s theory. It should be said that unforgivably little space is allotted in the book to the theory of hydrodynamic weather forecasting, successfully developed by Soviet scientists.

In general, the elements of synoptic meteorology to which Chapter XX is devoted are a weak point of the book. The author, to an insufficient extent, illuminates here the present-day achievements of science and the contemporary point of view on this question. Even allowing for the fact that in a general course on atmospheric physics it is impossible to devote much space to the important problem of weather prediction, the pages spent on this subject could have been used more rationally. For example, at the present time there is no need to set forth Petersen’s extrapolation method. But more space should have been given to the three-dimensional structure of cyclones and anticyclones, and apt examples illustrating it should have been selected. A fuller picture of the structure of typhoons could have been given on the basis of observations of recent years. It is unclear, incidentally, why Fig. 191 gives the principal tracks of typhoons only for the Pacific and Indian Oceans. One feels that in this chapter the author has not yet overcome the contradictions in the development of modern ideas about the causes of pressure changes, and has not managed to free himself from the outmoded and unscientific views of the so-called “advective-dynamic analysis.”

By contrast with the preceding chapter, the chapter on local winds makes a good impression, being one of the best chapters in the book. In it the author uses recent data, for example on atmospheric waves, discusses a number of new questions, etc.

The general circulation of the atmosphere is described interestingly and originally in the last chapter of the book. However, this chapter contains a substantial omission—the question of monsoons is considered in it insufficiently fully, and the theory is not compared there with sufficiently detailed factual material.

The book is not free of minor editorial shortcomings, misprints, etc. Thus, for example, inserts Nos. 64 and 145 have been interchanged.

On the whole, we must say that our comments have concerned mainly details of the exposition in the book. In summing up, it should be noted that the author has successfully coped with the task before him, one that was very complex and difficult. He has approached, in essence, in an entirely new way the exposition of the problems of modern meteorology or, as the author calls it, atmospheric physics. He has shown how a number of important problems of the atmosphere can be treated from the standpoint of modern physics and mathematics, using, to describe atmospheric phenomena, extensive modern observational material. The book will serve as a good aid for university students and graduate students, as well as for a broad circle of specialist meteorologists.

B. A. Aizshtat, V. A. Bugaev, V. A. Dzhordzhio