Videographic explaining the stage in the formation of a "cold drop" weather phenomenon which produces torrential rain and flooding, and is made worse by climate change VIDEOGRAPHIC
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00:00A cold drop weather phenomenon can cause torrential rain.
00:10It forms at the jet stream level, high in the atmosphere, where cold and warm air fronts
00:14meet.
00:15When the jet stream deforms, a pocket of cold air can separate from the main cold air mass.
00:20It ends up on top of the warm air and moves very slowly, remaining in the same place for
00:25days.
00:26The temperature difference between the two air masses produces instability.
00:31The humidity in the air condenses upon contact between the warm air and the cold drop.
00:36Large storm clouds, called cumulonimbus, can form and produce torrential rain.
00:41They can occur anywhere in the world, but cold drop weather phenomenon are frequent
00:45in the Mediterranean zone, because the air above the sea is often very humid.
00:50Climate change worsens this type of phenomenon because it causes higher sea surface temperatures
00:55and a warmer atmosphere, which can hold more moisture, producing heavier rainfall.
01:00However, cold drop phenomenon differs from the Mediterranean episodes, which occur when
01:05warm air from the Mediterranean is driven by the wind towards the coast.
01:09When it rises in altitude, this mild air then hits the cold continental masses, condenses
01:14and produces violent storms.
01:25For more UN videos visit www.un.org