Block of calculation of the solar radiation field in the general circulation model of the Earth's lower and middle atmosphere

This paper describes methods for calculating the solar radiation field in the radiation block of the general circulation model of the Earth's lower and middle atmosphere. These calculations use a new parametrization of molecular absorption in the frequency range from 2000 to 50000 cm$^{-1}$ in the altitude range from the Earth's surface to 100 km. The parametrization takes into account the change in the gas composition of the atmosphere with altitude, and also takes into account the violation of the local thermodynamic equilibrium in the vibrational bands of carbon dioxide with a wavelength of about 4.3 and 2.7 microns at altitudes above 70 km. For the numerical solution of the radiation transfer equation, the method of discrete ordinates is used. The results of calculations performed using the radiation block of the model are compared with the results of reference calculations of the solar radiation field in the lower and middle atmosphere of the Earth, performed with a very high frequency resolution. It is shown that the model block provides good accuracy of calculations both in the absence of clouds and in the presence of cloud layers with a large optical thickness.