THz wave background radiation at upper troposphere

THz wave has advantages in targets detecting and imaging, however, the severe atmospheric attenuation limits its application range. To perform a higher transmittance through clouds and higher resolution, upper troposphere should be considered to be the application senario of THz wave. Therefore, it is necessary to study on the atmospheric radiative transfer properties at different altitudes. Atmospheric Radiative Transfer Simulator (ARTS) was used to calculate path attenuation in 6 window frequencies selected, as well as 6 peak frequencies to analyze the difference. The brightness temperature and path attenuation at different frequencies and altitudes in different directions are calculated and analyzed. Results show that the brightness temperature in up-looking directions at 0.34 THz is smaller than 50 K for all altitudes which indicates small background noise, therefore, this frequency has great potential in targets detecting at all altitudes. At altitudes higher than 15 km, the brightness temperatures at all selected window frequencies are smaller than 50 K, which means that these frequencies also have potential in the targets detecting or imaging and the path attenuation is small, too. All 6 selected window frequencies have the potential for targets detecting in up-looking directions due to low attenuation and small background radiation. The calculations are all under the assumption of clear sky, the clouds will be considered in the further work.