Applications of meteorology and climatology to volcanic ash disruption Julian Hunt University...

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