VOLCANIC EMISSION FROM SATELLITE

CASE STUDY: 25 Nov 2005 - Karthala (Ash and So2)

SEVIRI IMAGES (6:12-15:42 UTC)

Volcanic eruption affect the signal in both spectral range, visible, near_infrared and thermal infrared region.
SEVIRI allow us to follow the event with a time resolution of 15min.
Here the foulse colore images prodice with the SEVIRI channels in the two spectral regions: thermal infrared and visible/near_infrared.

Thermal Infrared RGB=ch10-ch9,ch9-ch7,ch9	Visible (near infrared) RGB=ch3,ch2,ch1

ORAC RETRIEVAL using VIS and IR channels

To study this volcanic eruption an extended verison of ORAC algorithm have been applied, using the visible and infrared channels. As previouse developed for desert dust retrieval (SEVIRI dust retrieval)

Aerosol Optical Depth AOD at 550nm without data cut	Ash AOD (Ash plume = quality control + BTD less then average clean

Ash Effective Radius	Mass estimate [Tons/km^2] (assuming density = 1000kg/m^3)

	The total amount of ash mass in the atmosphere is considered as the sum of the estimate mass over all the plume pixels at the differents time. Becouse in this sum we consider only the pixel that have passed the quality control and are flagged like 'ash' this could be an underestimation. Infact the higher plume have a spectral behaviours that the ash model is not able to reproduce, probibly due to ice partiche that are present in the plume. The ash in the atmosphere arrive at maximum between 4 and 10am of 25th October 2005 and after begin to decrease.

Other sites and informations on Kartahala eruption:
Eumesat web page, NASA site: MODIS image

Maintained by Elisa Carboni