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SUMMARY:Microwave remote sensing of volcanic ash clouds. - Dr Mario Montop
 oli\, Dept. Geography\, University of Cambridge\,
DTSTART:20120521T131500Z
DTEND:20120521T143000Z
UID:TALK38332@talks.cam.ac.uk
DESCRIPTION:Plinian and sub-Plinian volcanic explosive eruptions probably 
 represent one\nof the most devastating natural events for the surrounding 
 environment\,\nendangering people's lives and property. Explosive volcanic
  eruptions can\nsignificantly influence climate as well as cloud formation
  and global\ncirculation through atmospheric transport. Volcanic ash cloud
 s are also an\nincreasing hazard to aviation safety because of growing air
 line traffic.\n\n    From the first rudimental visual inspections at the t
 imes of Pliny the\n\nElder\, the human curiosity and its needs to find eff
 ective countermeasures\nto these extreme volcanic episodes has never cease
 d\, even though their\n(fortunate) rarity makes the scientific research qu
 ite challenging.\n\nNowadays\, visual inspections are accompanied by sophi
 sticated measurements\nmade by direct analysis and from remote sensors. Mi
 crophysical\ncharacterization of the Plinian volcanic ash plumes is usuall
 y carried out\nby analyzing tephra deposits and ash sedimentation at groun
 d. This analysis\nmay only give indirect information on the ash cloud comp
 osition as several\nprocesses can take place during the ash fallout. On th
 e other hand\,\nreal-time monitoring of a volcano eruption is not always p
 ossible by\nconventional visual inspections due to the usual low optical v
 isibility.\nFinally\, airborne flights within ash plumes using sample prob
 es\, as done\nfor water clouds\, are considered too dangerous for the safe
 ty reasons\npreviously mentioned. Remote sensing techniques represent a un
 ique tool to\nbe exploited for this scope. They allow observing the evolut
 ion of some key\nparameters of volcanic eruptions without a direct interac
 tion between the\nmeasurement system and the target of the measure. Electr
 omagnetic or\nacoustic waves are usually used to this aim. Among the avail
 able remote\nsensing techniques\, satellite-based approaches\, using multi
 -frequency\nradiometers with visible and infrared channels\, have demonstr
 ated to be a\nvaluable supports to the monitoring of ash clouds. Moreover\
 , measurements\nin the visible spectral window are not always available du
 e to its solar\nillumination dependence and the optical thickness of volca
 nic clouds can\nseverely impair the sounding of lower cloud layers.\n\nIn 
 contrast with satellite methodologies\, ground-based microwave scanning\nw
 eather radars can gather three-dimensional information of ash-cloud\nscatt
 ering volumes with ranges up to several hundreds of kilometers\, in all\nw
 eather conditions\, at a fairly high spatial resolution (hundreds of\nmete
 rs) and with a repetition cycle of few minutes. So far\, these systems\nha
 ve been mainly used for meteorological operational forecasts and for\nobse
 rving of some small number of volcanic areas which can be monitored by\npr
 eviously installed instruments. There are also several open issues about\n
 microwave weather radar capabilities to detect and quantitatively retrieve
 \nash cloud parameters.\n\nAfter a basic introduction on remote sensing pr
 inciples\, the presentation\nwill focus at illustrating and assessing the 
 potential and limitation of\nmicrowave remote sensing of Plinian and sub-P
 linian volcanic eruption. This\nwill be done using examples from both grou
 nd based radar and satellite\nradiometers data\, collected after the 2010 
 and 2011 eruptions in Iceland.\nSome quantitative estimates of ash categor
 y and ash concentration will be\nshown together with explanations of the a
 lgorithms used.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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