This book is an introduction to atmospheric radiation. The focus is on radiative transfer in planetary atmospheres with particular emphasis on the Earth's atmosphere, the Earth's energy budget, and the role that radiation plays in climate sensitivity and climate change. The material is presented at the level expected of entering graduate students in the atmospheric sciences and most upper division undergraduates in the physical sciences. Students will need to have studied physics with calculus and methods for solving linear differential equations.
The goal of the book is to provide students with relatively simple physically based methods for calculating radiances and radiative fluxes at the Earth's surface and the top of the atmosphere and radiative heating rates within the atmosphere. It does so by following the approaches of two classical works: Rodgers and Walshaw , a treatment of infrared radiative transfer in the atmosphere, and Lacis and Hansen , a treatment of the transfer of solar radiation. Although more sophisticated treatments have appeared, these classical treatments embrace the physics of the problem. The difference in the modern and classical approaches is in the details with which scattering, absorption, and emission are treated and the numerical accuracy of the solutions to the radiative transfer equation.
The material presented in the book is intended to help students become familiar with relatively simple techniques that they can use to develop their intuition for the effects of scattering, absorption, and emission. A second goal is to alert students to the sensitivity of the Earth's climate to seemingly minor perturbations of the radiation budget. A third goal is to exercise a student's analytical skills. For the most part, the book's treatment is analytical. The use of large computer programs, while briefly described, is avoided. The emphasis is on helping students build an understanding that allows analytical manipulation rather than relying on computer exercises.
Problems at the end of each chapter are meant to be both interesting and instructive. They are intended to help students hone their understanding of the material covered in the chapter as well as in previous chapters. Some of these problems are rather simple but nonetheless helpful aids to learning; others will challenge students. The ordering of the problems is from the simple to the challenging. Occasionally, a problem will call for simple, straightforward numerical calculations that require the use of a spreadsheet or one of the widely used software programs for interactive computer analysis. These numerical exercises help students develop a sense of magnitudes for various processes.
This book grew from the "Class Notes" for a course on atmospheric radiation taught for more than 20 years at Oregon State University. Over the years, the notes evolved to better fit the needs of students and the time constraints of the 10-week quarter system. The book is not meant to be a reference book. Many fine references on atmospheric radiation already exist [3–8]. Teaching introductory courses from these references, however, has often proved difficult. Instructors are forced to select topics from what must seem to students as random pages from different sections of the books. Owing to time constraints, many sections of the books go untouched. In addition, some of the reference books are difficult for students to read. Some assume readers have far more advanced physical and mathematical knowledge and ability than have been acquired by many entering graduate students in the atmospheric sciences and upper division undergraduate students in the physical sciences. In fairness to the students, atmospheric radiation poses special challenges to those encountering the subject for the first time. New students often find bewildering the need for zenith angles, relative azimuth angles, sol