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.
Cloud physics
There are forces throughout the homosphere (which includes the troposphere, stratosphere, and mesosphere) that can impact the structural integrity of a cloud. However, as long as the air remains saturated, the natural force of cohesion that hold the molecules of a substance together acts to keep the cloud from breaking up. Dissolution of the cloud can occur when the process of adiabatic cooling ceases and upward lift of the air is replaced by subsidence. This leads to at least some degree of adiabatic warming of the air which can result in the cloud droplets or crystals turning back into invisible water vapor. Stronger forces such as wind shear and downdrafts can impact a cloud, but these are largely confined to the troposphere where nearly all the Earth's weather takes place. A typical cumulus cloud weighs about 500 metric tons, or 1.1 million pounds, the weight of 100 elephants.