Volcanic Aerosol Optical Depths during the post-Pinatubo era,

1996-2018Global values from Lunar Eclipse observations

RichardA.Keen,UniversityofColorado,Emeritus,DepartmentofAtmosphericandOceanicSciences,Boulder,CO80309;richard.keen@colorado.edu

Aboutonceperyear,onaverage,themoonistotallyeclipsed;themoonisthenilluminatedbysunlightrefractedintotheumbra,primarilybythestratosphere.Stratosphericaerosolscanaffectthebrightnessoftheeclipsedmoon,andclimaticallysignificant,visible-band,globalaerosolopticaldepth(AOD)canbedirectlymeasuredfromthedifferencebetweenobservedandpredictedbrightness.

Successfulobservationsofthetotallunareclipseof31January2018(thefirsteclipseinovertwoyears)bytheauthorandothersrevealthattheglobalvolcanicAODremainsatverylowlevels.A22+yearperiodofarelativelyclearstratospherethereforecontinues,andisthelongestsuchstretchsince1837- 1862.Thestratosphericimpactsofseveralclimaticallyinsignificantvolcanoesduring1996-2018areidentified.ThereisnotrendinAODoverthisperiod,rulingoutvolcanoesasacontributortothestableglobaltemperaturesduring1998-2015.Comparedtothevolcanicallyactiveperiod1980-1995(elChichon andPinatubo),theclearstratospheresince1995hascontributedanincreaseofradiativeclimateforcingequaltothatduetoincreasinggreenhousegases.

References:☽Hofmannetal.(2004)“Surface-BasedObservationsofVolcanicEmissionstotheStratosphere”,inVolcanismandtheEarth’sAtmosphere,GeophysicalMonograph139,AmericanGeophysicalUnion.☽ Keen(1983)“VolcanicAerosolsandLunarEclipses”,Science,2December1983:1011-1013.[DOI:10.1126/science.222.4627.1011]http://www.sciencemag.org/content/222/4627/1011.Presentationsatthe2015and2017NOAAGlobalMonitoringAnnualConferences(GMAC):☽ https://www.esrl.noaa.gov/gmd/publications/annual_meetings/2017/slides/7-Keen.pdf☽ http://www.esrl.noaa.gov/gmd/publications/annual_meetings/2015/posters/P-48.pdf

Research partially funded by a grant from the:

No animals, students, or retired faculty were harmed in this research.

Did the recent eruptions of these three historical

performers, Fuego, Agung and Mayon, actually perform?

Lunar Eclipse:Calculate a “predicted”

brightness for a clear atmosphere.

Observe the actual brightness, then

calculate the amount of volcanic stuff from

the difference.

Moon over Maui

No. The global volcano drought continues.

Kula View B&B

Cloudy

Clear

ThebrightnessofthemoondependsonitspaththroughtheumbraanddistancefromtheEarth.Knowingtheeclipse’sgeometry,the

moon’sbrightnesscanbepredicted(assumingnovolcanicaerosols).

The 3 AM scramble for clear skies was worth it – I was able to get some good observations.

ComparetheMoon’sbrightnesswith“nearby”stars

Presented at the 2018 Global Monitoring Annual Conference (GMAC), Boulder, CO, May 23, 2018.