"Gravity Wave" Cloud Structure (GWCS)
 The gravity wave clouds above the water surface are not often observed.
In contrast to much more frequently observing gravity wave clouds over the land, which normally above the lee side of mountains form and consist of long but not wide series, the gravity waves clouds above sea can have many hundreds kilometres long, but rarely more than 5-15 strips.
They are formed in a layer, which does not normally locate over 2 km, rarely over 3 km, above certain geographical regions.
A reason for the wave sample over the water surface is a formation of the clouds in a steady thin air layer, in which the air temperature does not change very much with the height.
The physical parameters of this layer do not differ from those that lie over and possible under it, and for the certain time the air of neighbour layers does not mix.
The possible air disturbance in the layer can cause the waves, along the border between this and framing layers.
If air in the layer is humid enough, clouds emerge in the place, where air rises up and cools.
These clouds float above the comb of the internal wave at the border to upper layer.
If air falls down to the wave trough, then clouds evaporate.
At most these structures were regularly observed within ±30° latitude over the ocean waters near coasts
- South Atlantic, close to east coast of the South America,
- Indian ocean
- South of the Mozambique channel,
- North of the Indian ocean,
- West of the Indian ocean, close to northwest coast of Australia.
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Global occurrence diagram of 'Gravity Wavesr' 
