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Lidar observations of Eyjafjallajokull ashes outbreak

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April 20, 2010 The Napoli Earlinet Lidar observed ash from Eyjafjallajokull starting in the morning of April 20, 2010, at around 3km height. Ash layer seeped into PBL in the eveningThe peak value of backscattering coefficient at 355nm (found at 18:50 UT, ~2 Km) increases from 2.2·10-6 sr-1 m-1 to 5·10-6 sr-1 m-1, and from 1.3·10-6 sr-1 m-1 to 3·10-6 sr-1 m-1 at 532nm.

April 21, 2010 Eyjafjallajokull ashes layer is present between 2 and 3 km in the first part of measurements. Night time data show the presence of ashes at high altitudes (5-8 Km) as well. 

April 22, 2010 Ash is detected at 2-3 Km and between 4 and 6 Km. Linear volume depolarization is always 1-3%.

April 23, 2010 Low clouds and rain prevent performing lidar measurements. Measurements will restart as soon as possible.

April 24, 2010 Low clouds and rain prevent performing lidar measurements. Measurements will start as soon as weather conditions will allow it.

April 25, 2010 Due to the presence of low clouds, measurements have been performed only between 14:37 and 17:00.
Aerosol layers are visible below 3 km and between  4 and 5.5 km ( clearly visible in the depolarization map). Backtrajectories indicate that the origin is in the Sahara region.

April 26, 2010 Several aersol layers layers are visible up to 5 Km of altitude. Linear depolarization  greater than 4 % between 2 and 4 Km, probably indicating Saharan dust ( in agreement with back trajectories). A layer with depolarization ratio of about 1.5 % is detected at 1 Km. Trajectories are compatible with remnant volcanic ashes.
April 27, 2010 Layers up to 2.5 Km, Linear volume depolarization and trajectories suggest a saharan origin. A thin layer at 3.5 Km, weakly depolarizing, is compatible with remnant volcanic ashes.
May 08, 2010
In Napoli the event is clearly visible. A strong depolarizing layer (linear volume depolarization about 10%) is at 4 km. Several other layers not depolarizing  are visible at 2Km, 3Km and 5 Km.
May 09,  2010
This morning the strongly depolarizing layer at 4 km is no longer present over Napoli. The most intense layer is at 2.5- 3 km( linear volume dep about 2%). Other layers are present below the main layer, they are  well distinguishable from the PBL, at least for now.
May 13,2010
Clouds prevented measurements in the morning. Starting from 13:00 layers are present at 1.5 Km, 2.0 Km, 2.5 Km. A strong signal is detected from 14:00 at 3 Km, corresponding to high value of linear volume depolarization ( >10%).
May 14,2010
Last night it was not possible to take any measurements due to low clouds.This morning we performed measurements among clouds. Aerosol layers ( probably mixed with saharan dust) appeared between 2 and 3.5 km. Beginning from 14:00 UT a more depolarizing layer appeared  between 3 and 5 km. Backward trajectories suggest the origin in Iceland. Messurements ahave been stopped at 17 UT due to low clouds. Rain is forecast until Monday, no measurements will be performed during the weekend.

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