The review below appeared in EOS (Transactions of the American Geophysical Union), Volume 81, Number 16, April 18, 2000.

Reviewer:

Jim Coakley, College of Oceanic and Atmospheric Sciences

Oregon State University, Corvallis USA

Radiative Transfer in the Atmosphere and Ocean

Gary E. Thomas and Knut Stamnes

Cambridge University Press, New York, NY,

xxvi + 517 pp., ISBN 0-521-40124-0, 1999, $85.

The Earth’s climate reflects the balance between the sunlight absorbed by the Earth-atmosphere system and the infrared radiation that the Earth emits to space. Change the composition of the atmosphere and the deposition of absorbed sunlight and the emission of infrared radiation by the atmosphere and surface are altered, upsetting existing balances, forcing temperatures to respond and the climate to change.

Understanding the transfer of radiation in the atmosphere is the key to anticipating the changes. In addition, with the recent launch of Terra, the first flagship of NASA’s Earth Observing System, observations of reflected sunlight and emitted infrared and microwave radiation are being used increasingly to probe atmospheric and surface processes as well as to monitor the various components and thermodynamic states of the climate system. There is clearly a need for textbooks that introduce newcomers to radiative transfer, given its central role in climate and remote sensing. The landmark references by S. Chandrasekhar [1950] and R.M. Goody [1964] served as introductions to radiative transfer for many of today’s practitioners, but they were not meant to be textbooks and have proven unwieldy when pressed into that role. This new book should fulfill this need.

In 12 chapters, and 5 appendices, with additional appendices to be made available on a Web site, the book provides a lucid and reasonably complete, practical treatment of the fundamentals of plane-parallel radiative transfer theory in the atmosphere and the ocean and the exchange of radiant energy between the atmosphere and ocean. The book is easy to read, and there are many examples to illustrate the concepts discussed in the text. Each chapter is followed by thoughtful problems. The focus is on heating and energy exchange; applications in remote sensing are not discussed. The book is remarkably free of errors, and the few errors that I managed to uncover were of little consequence.

Chapter 8 is the book’s cornerstone. It provides a thorough highly readable account of the discrete ordinate method for solving the equation of radiative transfer. This method was pioneered by Chandrasekhar but honed to a precision tool in the form of the readily available DISORT radiative transfer code by Stamnes and his coworkers. The chapter covers the many facets of the discrete ordinate method that have appeared in numbers, sometimes hard to obtain, journal publications during the past 2 decades. Students will find helpful the analytical treatment of the two-stream approximation, which chapter 7 probes in great detail. The two-stream approximation is the low-order form of the general, multistream discrete ordinate method, and it is employed to illustrate the procedures used to solve the multistream problem. The book only briefly touches on other approaches, such as the adding-doubling and Monte Carlo methods.

Another noteworthy feature is the book’s treatment of the interaction of radiation with matter. Chapter 3 is devoted to scattering, chapter 4 to absorption. These chapters are not meant to provide the background one gains through reading other books on these subjects but, instead, rely on simple models, such as the harmonic oscillator and the rigid rotor molecule, to introduce concepts such as the scattering phase function, spectral line shape, and line spacing. For those who have backgrounds in electricity and magnetism and atomic and molecular spectra, these chapters offer delightfully thoughtful reviews. Ultimately, when it comes to the treatment of scattering within molecular absorption bands, students will again appreciate the analytical derivation of k-distributions for single, pressure-broadened, absorption lines as illustrations of the general approach to approximating the transfer of broadband radiation with a series of monochromatic calculations.

The book should serve well as an introduction to radiative transfer. My only reservation is that for applications, chapter 12 investigates the Earth’s energy budget by modeling the atmosphere as window gray, sometimes in radiative equilibrium and sometimes in radiative-convective equilibrium. True, the model, which relies on the two-stream approximation, is analytic and when properly tuned also produces longwave fluxes and albedos that seem realistic when compared with those at the top of the Earth’s atmosphere. However, the Earth’s atmosphere is definitely not gray, and one wonders whether the agreement with observations simply reflects the limited range of possible outcomes rather than a measure of success in describing the major physical processes. Numerical calculations for the Earth’s atmosphere in radiative equilibrium put the stratospheric temperature (without ozone, as in the window-gray model) at 160 K, not 214 K, as obtained by the window-gray model, and is close to the average temperature of the lower stratosphere [Manabe and Strickler, 1964]. In chapter 12, as in chapter 7 on the two-stream approximation, the presentation appears to get caught up in the simplicity and analytical aspects of the approximations.

For a finale, I would have preferred seeing comparisons of calculated and observed radiation fields that would have illustrated the successes and failures of the theoretical methods that had been presented. Unfortunately, few such comparisons have been undertaken in the literature and most of the comparisons have focused on problems related to remote sensing. With the advent of the Earth Observing System, observations will abound. Still, it may take years to sort through the best of observations and align them with the most suitable calculations to provide a fitting final chapter for a book such as this.

References

Chandrasekhar, S., Radiative Transfer, Clarendon Press, Oxford, 1950, reprinted by Dover Publications, New York, 393 pp., 1960.

Goody, R. M., Atmospheric Radiation, Theoretical Basis, (second edition by R. M.

Goody and Y. Yung), Oxford University Press, 436 pp., 1964, 519 pp., 1989.

Manabe, S., and R. F. Strickler, Thermal equilibrium in the Atmosphere with a convective adjustment, J. Atmos., Sci., pp. 361-385, 1964.