Impacts of major factors on downward longwave radiation

Downward longwave irradiance (DLI) is important to understand climate change. To estimate the impact of major GHGs and regional change for downward longwave radiation, we used the observation data in five different climate regions, which are sites of the Baseline Surface Radiation Network (BSRN), and evaluated the contribution fraction (CONF) for DLI quantitatively with mstrn×, which had 14 bands for longwave radiation. The impact of variation of WV was strong in the bands from 2 to 3 (40-18.9 μm) under clear-sky condition. CONFs of WV were small in the bands from 4 to 6 (18.9-14.9 μm) because of the strong overlapping with CO₂ in 15 μm absorption bands.