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Context:

Flash floods caused by the immense deluge have led to the death of at least 64 people in the eastern Spanish region of Valencia.

What is DANA or cold drop?

DANA or cold drop takes place when cold air descends over the warm waters of the Mediterranean Sea. This results in atmospheric instability, causing hotter, moist air on the surface of the sea to rise quickly, leading to the formation of dense, towering cumulonimbus clouds in a matter of hours. These clouds then dump heavy rain in parts of Spain.

Formation

The weather pattern’s occurrence is related to the polar jet stream — a fast-moving wind current at high levels of the troposphere (the lowest layer of Earth’s atmosphere) which circulates from west to east and separates the cold polar air from the warm tropical air.

Mechanism

The phenomenon is a common occurrence in Spain and usually coincides with the onset of autumn and spring in the western Mediterranean. As per experts  the rains caused by a cold drop no longer just hit the coast, but also cities like Madrid, “where it is not usual to have this type of abundant rainfall.”

Reason for its occurrence

It happens partly because of soaring global temperatures — warmer air can retain more moisture which, in turn, results in more intense rainfall. The rise in sea surface temperatures of the Mediterranean Sea has also exacerbated the situation. In August, the sea touched its highest-ever recorded temperature.

NOTE- DON’T GET CONFUSED WITH THE CYCLONE DANA (https://www.iasgyan.in/daily-current-affairs/cyclone-dana)

Source:

Indian Express