Improved method of exponential sum fitting of transmissions to describe the absorption of atmospheric gases.

For climate modeling and atmospheric research, such as investigations of global climate change, remote sensing of cloud properties, or the missing absorption problem in clouds, it is most important to describe adequately the absorption of radiation by atmospheric gases. An improved method for the exponential sum fitting of transmissions (ESPT) is developed to approximate this absorption accurately. Exponentials are estimated separately for any number of atmospheric-model layers, considering the pressure and temperature dependence of the absorption lines directly. As long as the error of the fit exceeds a limit of tolerance, the number of considered exponential terms is successively increased. The accuracy of the method presented yields a root-mean-square error of less than 0.03% for any atmospheric-model layer, whereas the commonly used one-layer techniques gain errors of up to 3% in the transmission functions for the upper layers. The commonly used ESPT methods consider only one atmospheric layer and introduce the pressure and temperature effects for the other model layers afterward.

[1]  K. Liou,et al.  On the Transfer of Solar Radiation in Aerosol Atmospheres , 1975 .

[2]  J. Hansen,et al.  A parameterization for the absorption of solar radiation in the earth's atmosphere , 1974 .

[3]  J. Fischer,et al.  Detection of Cloud-Top Height from Backscattered Radiances within the Oxygen A Band. Part 1: Theoretical Study. , 1991 .

[4]  V. M. Devi,et al.  THE HITRAN MOLECULAR DATABASE: EDITIONS OF 1991 AND 1992 , 1992 .

[5]  Louis Kouvaris,et al.  Monochromatic calculations of atmospheric radiative transfer due to molecular line absorption , 1986 .

[6]  John A. Nelder,et al.  A Simplex Method for Function Minimization , 1965, Comput. J..

[7]  Peter H. Stone,et al.  Efficient Three-Dimensional Global Models for Climate Studies: Models I and II , 1983 .

[8]  R. Davies,et al.  Radiation and cloud processes in the atmosphere , 1992 .

[9]  A. Uchiyama,et al.  Application of an extended ESFT method to calculation of solar heating rates by water vapor absorption , 1987 .

[10]  M. Chou,et al.  Atmospheric Solar Heating Rate in the Water Vapor Bands , 1986 .

[11]  N. Scott,et al.  A direct method of computation of the transmission function of an inhomogeneous gaseous medium— I: Description of the method , 1974 .

[12]  A. Arking,et al.  An Efficient Method for Computing the Absorption of Solar Radiation by Water Vapor , 1981 .

[13]  G. L. Stephens,et al.  Radiation Profiles in Extended Water Clouds. I: Theory , 1978 .

[14]  Si-Chee Tsay,et al.  On the cloud absorption anomaly , 1990 .

[15]  A Goldman,et al.  The HITRAN database: 1986 edition. , 1987, Applied optics.

[16]  W. Wiscombe,et al.  Exponential-sum fitting of radiative transmission functions , 1977 .