Black Sea cyclone, Gallery. RDC ScanEx

Gallery

Title
Black Sea cyclone

Acquisition date
02.12.2001

Sensor
Terra, MODIS

796 x 599
JPEG (742 kb)

Black Sea cyclone

MODIS imaging instrument image acquired on 02.12.2001 expressly demonstrates the type of the atmospheric circulation over the area spreading from the eastern part of the Black Sea to the Lake of Sevan, Armenia. The eyewall structure allows defining for sure that the most part of the image is covered with a wide high cyclone over the Black Sea, coming along the southern margin of the polar front. Long-term weather deterioration occurs when such a high cyclone is developing over the Black Sea.

Cyclone (from the Greek kyklon – spinning, whirling) – is an atmospheric vortex from a hundred to several thousands kilometers in diameter with a lower air pressure in the center. Powerful cyclone whirling is created as a result of the Earth rotation on the boundaries of atmospheric fronts, dividing cold and warm air masses, therefore cyclones move primarily along the atmospheric fronts from west to east at a speed of 30-50 km/h. Wind system inside a cyclone circulates from the outskirts to the center and in counterclockwise direction in the Northern hemisphere and clockwise – in the Southern, with a deviation to the cyclone center in the lower atmosphere due to pressure decrease.

As both atmospheric fronts meet in the cyclone center, there is an area between them with a warm air mass, the so-called warm cyclone center, with cold air mass prevailing in the other part of the cyclone. Reaching the central part, the cold air rises and spreads towards the periphery.

The rising air expands and cools down; the vapor condenses, generating clouds and precipitation. Therefore rainy, windy and murky weather prevails along the cyclone path: chilly and rainy due to clouds in summer and with snowfalls and thaw in winter. Plumeous clouds and lower pressures are the first messengers of the approaching cyclone. IT is important to define during the weather forecast which part of the cyclone will pass through the region of interest, as weather property differs through the cyclone. Wind direction changes monitoring may help resolve this task. The opposite of a cyclone in the general atmospheric circulation system is a anticyclone with a different creation mechanism. There are two basic cyclone types – extratropical and tropical. In this case, the image depicts a Black Sea cyclone, which a southern extratropical cyclone created on the southern border of midlatitudes and moving north-east and east, covering the piedmont and valleys between the Caucasian mountain range and the Armenian uplands. Southern cyclones have an expressly marked temperature asymmetry: snowfalls and blizzards in winter, with heavy torrential rains, and thunderstorms in summer. In addition, southern cyclones are characteristic of colossal accumulated energy, thus bringing heaviest rains, winds, thunderstorms, squalls and other acts of weather both onshore and offshore.

Title:	Black Sea cyclone
Acquisition date:	02.12.2001
Sensor:	Terra, MODIS

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mailto: webmaster@scanex.ru