The contribution of unknown weak water vapor lines to the absorption of solar radiation

Thousands of unknown water vapour weak lines in the spectral region between 13200 and 22700 cm(-1) are deduced from extrapolations of experimental res ults. These lines are then included in the HITRAN database and used in line -by-line calculations of atmospheric opacity with standard atmospheric prof iles. The weak lines predicted by a theoretical model are also used in the line-by-line model to estimate their contribution to the absorption of sola r radiation. The additional absorption of solar radiation is of order 1.5 t o 2.5 W/m(2) at 45 mm precipitable water, about 8.5% to 14% of the absorpti on due to HITRAN lines in the spectral region. The effect is also compared with that of a continuum model.