The downward solar radiation (shown in black) here is the visible light evident directly from the sun. Upward reflected radiation (shown in green) is sunlight which has been reflected off the Earth's surface. We expect downward radiation to be much higher than upward radiation in most cases. Points in winter where levels of reflected radiation are close to levels of downward radiation are where there is snow on the ground, since snow is very reflective.

The blue line here shows individual readings of background radiation counts, which varies greatly. Shown in white are the 5 minute moving averages for the data, which show that background radiation is roughly constant over time. The increases in geiger counts in the winter are discussed below.

The cosmic ray flux varies with space weather activity and atmospheric pressure. Normally we record very few counts (typically 3-10 per day) because our detector has a small area. A larger detector would measure more counts, but is more difficult to maintain at the “space station” due to its limited power. When the weather is very cold we record many more counts. The reasons for this are under investigation, but do not seem to be caused by faulty instrumentation.

Standard air pressure at Sea level is 1013hPa, or 1 atmosphere. Air pressure decreases as height above sea level increases, so we expect the average pressure at the summit of Mount Snowdon to be around 890hPa. There is some variation in air pressure, and this affects the weather. High pressure patches are associated with clear skies, while low pressure is associated with cloud, rain and snow.

Longwave radiation refers to radiation in the infared spectrum, which is the same as heat. This isn't necessarily directly from the Sun, it is also emitted or reflected by clouds or the Earth. Higher levels of longwave radiation indicates cloud cover.