The highest shortwave radiation readings occur in the summer (June) and their daily average are about 350 W/m2 in Payerne, Locarno-Monti and Davos, and reaching 400 W/m2 at the Jungfraujoch. In winter, the values are much lower - in general by a factor of around four.
In addition to the aforementioned factors, the intensity of solar radiation also depends on the concentration of aerosols (Aerosol monitoring) in the atmosphere, which is also referred to as aerosol optical depth. This is a measure of the transparency of the atmosphere. On the Jungfraujoch, for example, the aerosol optical depth is typically very low, but it is affected by strong disturbances such as the incursion of mineral dust from the Sahara [LINK] or by local emissions from neighbouring valleys.
Cloud cover has a significant effect on both solar radiation as well as thermal radiation, although the effects on these two domains are generally opposite to each other. Although clouds more often than not reduce the intensity of solar radiation, they normally increase thermal radiation and retain the heat in the low layers of the atmosphere.
The highest longwave radiation values occur in the summer (at the end of July and in August) and are in the order of 400 W/m2 in Payerne and Locarno-Monti, 350 W/m2 in Davos and a little over 300 W/m2 on the Jungfraujoch. In winter, the values are much lower - in general around 200-250 W/m2.