Critical discussion on the UV absorption properties of Earth's atmosphere

摘要

Sun's ultraviolet radiation is classified into UV-A, UV-B, and UV-C bands. Thereby UV-A passes through Earth's atmosphere, while UV-B is partially absorbed by ozone. The limitations of the commonly accepted statement, that UV-C is always completely absorbed by Earth's atmosphere, are discussed critically. Below 200 run the solar spectrum is strongly absorbed by molecular oxygen. The stratospheric ozone layer has strong absorption between 200 nm and 300 run. However, the "ozone hole" increases UV-B radiation just below 300 nm and may also open a transmitting atmospheric window for harmful UV-C at the overlap region between oxygen absorption and ozone absorption.