Approximate methods for finding CO₂ 15‐μm band transmission in planetary atmospheres

Abstract

The CO 2 15-/•m band provides an important source of thermal opacity in the atmospheres of Venus, Earth, and Mars. Efficient and accurate methods for finding the transmission in this band are therefore needed before complete, self-consistent physical models of these atmospheres can be developed. In this paper we describe a hierarchy of such methods. The most versatile and accurate of these is an "

Development of a fast, accurate radiative transfer model for the Martian atmosphere, past and present

“…During the past several decades, a number of approaches were developed to tackle the problem of radiative transfer on present‐day Mars [ Pollack et al , 1981; Crisp et al , 1986; Pollack et al , 1990; Hourdin , 1992]. Typically, these approaches took the form of wide‐band models, and took an empirical approach to reproducing the amount of atmospheric absorption present in the infrared and visible spectrum within spectral bands of greatest absorption.…”

“…While the dominant radiatively active component of the present Martian atmosphere is carbon dioxide (95.3% by volume), and other radiatively active gases are found only in trivial amounts (water vapor being key among these), during past epochs, the environment was substantially different, likely with a thicker CO 2 atmosphere and a greater abundance of other gases, potentially including H 2 O, sulfur dioxide, methane and others, each of which may have been radiatively significant for either short durations, or for longer periods. 1 [3] During the past several decades, a number of approaches were developed to tackle the problem of radiative transfer on present-day Mars [Pollack et al, 1981;Crisp et al, 1986;Pollack et al, 1990;Hourdin, 1992]. Typically, these approaches took the form of wide-band models, and took an empirical approach to reproducing the amount of atmospheric absorption present in the infrared and visible spectrum within spectral bands of greatest absorption.…”

Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated‐k model for the longwave

“…Band models [e.g., Goody, 1952;Kieht and Ramanathan, 1983;Crisp et al, 1986] are capable of providing accurate results in clear-sky conditions. However, since these models do not possess detailed information about the absorption coefficient distribution, their formalism does not readily lend itself to the calculation of radiative transfer for scattering atmospheres, which is highly dependent on the magnitude of local absorption.…”

A three‐parameter approximation for radiative transfer in nonhomogeneous atmospheres: Application to the O3 9.6‐μm band

“…This is because the ozone profile is characterized by the combination of large concentration at low pressure and small concentration at high pressure. For this reason, the two-parameter Curtis-Godson (CG) and other conventional scaling approximations, which may work well for the H20 and CO2 bands, fail to provide accurate results in nonhomogeneous atmospheres for the 03 9.6-/•m band [Curtis, 1952;Walshaw and Rodgers, 1963;Kratz and Cess, 1988].…”

“…In the calculation of atmospheric transmission the vertical nonhomogeneity must be accounted for. The conventional approach that has been used is the so-called Curtis-Godson (CG) method [van de Hulst, 1945;Curtis, 1952;Godson, 1953]. The CG approach reconstructs a homogeneous path for which the transmittance is approximately the same as that for the actual path, namely,…”