Broadcast range
The local terrain can also play a major role in limiting broadcast range. Mountain ranges block FM broadcasts, AM broadcasts, and TV broadcasts, and other signals in the VHF and especially UHF ranges, respectively. This terrain shielding occurs when the line of sight is blocked by something through which the radio waves cannot pass, particularly stone. At times this may be moot due to weather, such as when the tall cumulonimbus clouds of a squall line of thunderstorms reflect the signal over the top, like an extremely tall radio tower. Conversely, heavy rain may attenuate the range of even local stations. ATSC digital television is affected by wind and trees (even if not surrounding the transmitter or receiver locations), apparently related to its use of 8VSB modulation instead of COFDM.
Jasper Kirkby
The CLOUD experiment is investigating possible physical mechanisms for "solar/cosmic ray forcing" - a theory whereby cloud nucleation is affected by cosmic rays and the cosmic rays are affected by solar activity. The main purpose of the CLOUD experiment is to simulate the conditions under which clouds form in earth's atmosphere--specifically, the process by which cloud condensation nuclei form from aerosols in the atmosphere. Kirkby et al. published the results of CLOUD's first experiment in the journal "Nature" in 2011, reporting that cosmic rays "seemed to enhance the production of nanometre-sized particles from the gaseous atmosphere by more than a factor of ten." He added, however, that the particles in question are far too small to serve as cloud condensation nuclei, adding, "At the moment, it actually says nothing about a possible cosmic-ray effect on clouds and climate, but it's a very important first step."