Calculation Block of the Solar Radiation Field in the General Circulation Model of the Lower and Middle Atmosphere of the Earth

The methods for calculating the solar radiation field in the radiation block of the general circulation model of the Earth’s lower and middle atmosphere are described. These calculations use a new parametrization of molecular absorption in the frequency range from 2000 to 50 000 cm –1 in the range of heights from the Earth’s surface up to 100 km. The parametrization takes into account the change in the gas composition of the atmosphere with altitude and the violation of the local thermodynamic equilibrium in the vibrational bands of carbon dioxide with a wavelength of about 4.3 and 2.7 μm at altitudes above 70 km. The method of discrete ordinates is used for the numerical solution of the radiative transfer equation. The results of calculations performed using the radiation block of the model are compared with the results of the 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 calculation accuracy both in the absence of clouds and in the presence of cloud layers with a large optical thickness.