Advanced broadband parameterizations for calculation of the solar radiation absorption by water vapor

The additional absorption of solar radiation by water vapor in the line-by-line model due to the use of the spectral database by Patridge and Schwenke (1997) instead of the less detailed HITRAN-96 database is discussed. For the tropical atmosphere (H2O absorption only) and solar zenith angle of 30degrees, its magnitude in the total near infrared region is noticeable and riches 7.7 W m(-2). Together with the shortwave continuum absorption it gives 19.9 W m(-2). The broadband parameterizations taking that absorption into account have been developed using the k-distribution technique. For the three standard atmospheres and solar zenith angles of 30 degrees the error in the absorption values computed by using the parameterizations is less than 2.0 W m(-2) as compared with the benchmark values obtained by the line-by-line model. The error in the heating rates is less than 0.1 K/day at most of the atmospheric levels.