An estimation of the UV radiation inside the cockpits of large commercial jets

UV irradiances and UV doses inside the cockpit of large commercial jets are estimated. Results are based on radiative transfer calculations taking into account the spectral transmittances and the limited fields of view of large commercial jet windscreens. In a first step, vertical profiles of UV irradiances for a cloud free atmosphere over snow free and snow covered surfaces and for an atmosphere containing a water cloud layer are simulated. It turns out that the windscreens block the UV-B radiation and transmit parts of the UV-A radiation. Comparing UV irradiances inside and outside the cockpit show that the intensity of UV radiation inside strongly depends on whether the direct sun is entering the cabin or not. Without direct sun the diffuse UV radiation inside the cockpit amounts to about 5% the ambient UV irradiance outside the aircraft. In cases of low sun when direct radiation can reach the pilot, percentages grow from 50 to 100% with increasing solar zenith angle. A water cloud layer between 2 and 4 km increases the UV irradiances inside a cockpit by about 7% at 10 km altitude when compared to the cloud free atmosphere. A snow covered surface causes a similar increase. Finally, and by the aid of MOZAIC waypoint data UV doses were estimated for selected long-distance flights between Europe and the overseas continents North and South America, South Africa, and East Asia. UV doses are affected by takeoff and landing time, by the sun position relative to the aircraft heading during flight, and by the day of the year. UV doses inside the cockpit amount to maximum 60% the UV doses outside at the same altitude, however, in most cases percentages are between about 10 and 40%.