applications of meteorology and climatology to volcanic ash disruption julian hunt university...
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Applications of meteorology and climatology to volcanic ash
disruption Julian Hunt
University College, LondonUniversity of Cambridge
TU Delft House of Lords
Met. Background ; warnings ; institutional arrangements ; future concerns/possibilities /proposals
Volcanic plumes • Height depends on speed, size, temp of eruption ie Fb(but not v sensitive)
and background stability of atmos N (H~F\(1/4) . N\(-3/4) ~ 10km +/-) -also verified by nuclear explosions (ie Fb can be unsteady).• Depth of plume much less than H –contains most of the eruption.; plume
moves with wind U(z) , z=H.• But if Fb varies -> variation of H-> plume spread over wider area, and greater depth since U varies with (z) .
• Plume physics; lightning induced in plume cloud-detected remotely (Met office atd-on web) ;
Plume cloud spreads by mean flow gradients dU/dz and turbulence
cloud affects radiation , temp, turbulence, precip. (regional effects on crops -1780’s;Pinatubo reduces global temp by 0.2 deg
for about 2 years -1992)
Zones in the atmosphere
• Upper atmosphere –above 10km Ionosphere, mesosphere- electrical signals ; waves ( as
induced by convection in some equakes/volcanoes –Russian research-Maths Today june 2010)
• Stratosphere (10-100km)-stable, weak turbulence, thin clouds-particles carried around the world-long range aircraft -high vol. plumes
(ozone hole dynamics and chemistry)• Troposphere –below tropopause at 10km Mixture of stable /convective/cloud motions 10km-
1000km -particles carried over continental scale ,-typical volc plumes – short range aircraft
-in relation to height of volcanic plumes
Long range dispersion –depending on ‘synoptic conditions’ (Maryon/Buckland studies 1995)
• Particles carried by wind at different heights leads to spreading , but v slow dry deposition.
-in usual westerly winds volc.(also chimneys/fires) plumes are as deep as the initial plume and carried within weather patterns-(1000km) ->deposition at fronts( if plume is in troposphere).
-in blocked flows (easterly winds over europe ) plumes travel slowly and recirculate (eg Chernobyl; Iceland )-can thicken with convection
• -can preclude aircraft paths around/under plume.
Cloud patterns related to synoptic weather structures
• Note that dust moves through similar structures –mixing and deposition near fronts –where clouds swirl.
Forecasts of dispersion
• Overall plume forecast -Requires accuracy at all levels of plume; * accuracy needed where flow patterns change –esp from/to deep blocking . (note 5-10 days possible –but timing may be in error)
• * cloud/dispersion processes have to be modelled ( note detailed simulations on Jap earth sim.)
Typical storm event for NW Europe – plus NS pressure gradient (NAO <0)
Images from the Houze Cloud Atlas http://www.atmos.washington.edu/gcg/Atlas/
Clouds and Climate
Low clouds reflect sunlighttrap little infra-red radiation
High thin clouds reflect less sunlighttrap more infra-red radiation
High deep clouds.reflect and
trap infra red
connections between particles , clouds , rain are critical for climate
V small particles can cause v small droplets & clouds , but no rain
-observed in urban areas; may be significant for cosmic ray(XT) particles
Note low sun spots -> less XT particles ; variable rain (1600 -1750)
Small scale structure (1-10mm) of turb eddies –now revealed on Jap Earth Simulator. Tiny Vortices within thin shear layers -> possibility of modelling cloud droplets and effects of dust particles etc (collab europe-japan)
Global Scale 2-D Eddies(McIntyre)
Sheltering
Shutts 1983
Disappearing eddies stronger front
• 1. Emission Agencies (IAVCE for volcanoes; IAEA for nuclear ; regional/national for pollutants/ forest fires)
• 2. Atmospheric agencies for dispersion, deposition , chemical transformation (WMO + ICSU(?), national met services)
• 3. Agencies for impacts (ICAO for air traffic; WHO –health , FAO ag/forestry etc IAEA for radio active )
International warning systems for effects of large emissions into the atmosphere.
Operation of warning systems
• 1. agreement between emissions/atm/impacts agencies ;(eg Iavce, wmo, icao; wmo , iaea in 1990’s)
• 2. Regular testing of communications and operation of systems (eg nat met serv comparing test cases)- the volcanic ash incidents since 1990’s had been handled ; and air traffic adjusted to warnings .
• 3. Also testing needed to include systems and Interests affected by large emissions- this situation –For the 2010 Iceland volcano this had not been done
(Note operational and risk analyses of such a complex system -needs to be done in future GSDP)
4. Note that with bigger impact events greater interest in higher risk operations, eg aircraft moving around ash clouds-is the forecasting good enough?
SCHEMATIC DIAGRAM OF CLIMATE CHANGE PROCESSES
Less snow/ice -> more volcanoes?
1. Regimes
CASSOU & GULYARDI 2007
Significant likelihood of more/longer blocking events –with deeper convection.
Conclusions and recommendations
• Development in volcano warning and monitoring world wide (new/open multi-disciplinary technology –satellites/sferics/elec fields) -+Russia-Jap
• Forecasts improving-but better physics needed esp in cloud processes (+jap es)
• More effective use of data and forecasts for operations and for risks –complex system methods needed.(GSDP project –needs to be part of international control/planning system)-
• Note some scientific and operational similarities for different large atmospheric emission problems.
• Governments and research agencies should collaborate more closely with the UN agencies –often ignored-> duplication
(EU/EC needs new mechanisms for its projects to integrate with UN operations /programs).
Waves
Waves
Turb
Turb