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.
Sea ice concentration
Because clouds are translucent in the microwave regime, especially
at lower frequencies, microwave radiometers are quite weather insensitive.
Since most microwave radiometers operate along a polar orbit with
a broad, sweeping scan, full ice maps of the polar regions where
the swaths are largely overlapping can usually be obtained within one day.
This frequency and reliability comes at the cost of a poor resolution:
the angular field of view of an antenna is directly
proportional to the wavelength
and inversely proportional to the effective aperture area.
Thus we need a large deflector dish to compensate for a low frequency