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Measurements from early morning 23 May 2011. Two ash layers can be detected, at altitudes of 500 and 1200 m.
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Ash measurements

24.5.2011

Recently, the IMO  obtained a LIDAR (Light Detection and Ranging)  on loan from the National Centre for Atmospheric Science (NCAS) in the UK. The instrument transmits laser beams into the atmosphere and measures the light that is backscattered towards the ground.

The instrument was installed on the lowlands close to the volcano Eyjafjallajökull which erupted last year. The aim was to measure windblown resuspended ash  from last year's eruption.  Following the eruption at Grimsvotn it was on  May 22nd  moved to the Keflavik International Airport in Keflavík  in order to detect ash if as was present in the atmosphere above the airport.

The IMO owns a weather radar which is situated on Miðnesheiði, close to the Keflavík airport. The main purpose of the weather radar is to monitor precipitation, but the but raindrops scatter the microwave radiation from the radar and the the backscatter is measured by the radar. The radar has also been successfully used in monitoring eruption plumes, recording reflections  from ash particles and water droplets in the  plume.

The weather radar on Miðnesheiði
kort - sammiðja hringar út frá Keflavík
The image shows the radar backscatter signal recorded at 14:20 hrs on 23 May 2011. Also, the maximum backscatter in the vertical plane is shown, which can be used in estimating the height of the plume. At this time, the plume reached heights of 8 - 12 km.

During the 2010 Eyjafjallajökull eruption, the weather radar proved to be a very useful tool, but the great distance to the eruption site (160 km) reduced the quality of the data. Therefore, a mobile X-band weather radar was purchased, but while this custom made radar was being assembled and tested, another was obtained on loan from the Italian Civil Protection Agency. The mobile radar is now situated near the town of Kirkjubæjarklaustur, 80 km from the eruption site in Grímsvötn. IMO staff members monitor the  progress of the  eruption using the two weather radars.

The mobile weather radar
kort - sammiðja hringar út frá Keflavík
The mobile radar, which is only 80 km from the eruption site, shows enhanced scattering in the eruption plume. The image gives greater detail than can be observed with the radar in Keflavík. The map shows the reflection that the radar measured at 14h on 23 May 2011. Also, the maximum reflection in the vertical plane is shown which is used to estimate the height of the plume. When this image was taken, the plume reached heights of 6 - 8 km.



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