http://phys.org/news/2013-02-violent-nabro-eruption-shown-pierce.html
Violent Nabro eruption shown to pierce stratosphere
February 8, 2013
(Phys.org) - Researchers from the U.S. Naval Research Laboratory Ocean
and Atmospheric Science and Technology Directorate report conclusive
evidence that volcanic gases and aerosols from the explosive 2011
eruption of the East Africa Nabro Volcano breached the stratosphere,
unassisted by the seasonal Asian monsoonal flow.
Read more at:
http://phys.org/news/2013-02-violent-nabro-eruption-shown-pierce.html#jCp
On June 12, 2011, the Nabro Volcano explosively erupted, forcing
sulfur dioxide (SO2) gas and volcanic aerosols high into the
atmosphere. Prior analyses had suggested the Nabro plume reached the
stratosphere only after being transported through a tropospheric
meteorological phenomenon associated with the Asian Monsoon
circulation.
"There is overwhelming satellite evidence that the Nabro eruption
caused a sizable and direct volcanic impact on the stratosphere," said
Mike Fromm, NRL research meteorologist. "Robust satellite data
indisputably indicate volcanic gases and particles penetrated the
stratosphere during the initial eruption and a second eruption three
days later."
Thermal infrared (IR) imagery captured by the NASA Moderate Resolution
Imaging Spectroradiometer (MODIS) satellite two hours after the
eruption provides overwhelming evidence of a deep convective umbrella
cloud with locally cold temperatures in a peripheral arc and warmer
temperatures near the cloud center, a signature of violent convection
associated with breaches in the lower stratosphere.
To characterize the Nabro plume, NRL scientists use three instruments
from NASA's 'A-Train' constellation - a series of quasi-simultaneous
nadir and limb viewing measurement satellites that orbit Earth one
behind the other. MODIS, onboard the satellite Aqua, acquires spectral
data on global dynamics and processes occurring on land, in oceans,
and in the atmosphere. The Ozone Monitoring Instrument (OMI), onboard
the Aura satellite, distinguishes between aerosol types such as smoke,
dust, and sulfates, and measures data to derive ozone. The Microwave
Limb Sounder (MLS), also onboard Aura, provides measurements of
atmospheric composition, temperature, humidity, and cloud ice. Data
taken from the OMI shortly after the eruption indicate scattering
volcanic aerosols such as liquid sulfate droplets and SO2.
Observations from MODIS IR cloud-top temperatures revealed that an
optically opaque volcanic cloud covers the same area as the OMI AI
plume with a minimum IR brightness temperature of minus 78 degrees
Celsius, a lower stratospheric value.
"Ultraviolet backscatter sensors such as OMI are sensitive and cannot
'see through' optically thick clouds, indicating the signal of
scattering aerosols and sulfur dioxide originated from altitudes above
this high cloud top," says Fromm. "The opaque cloud surface also
guarantees that no information from the troposphere below is
obtainable."
The day after the eruption, height-resolved SO2 data retrieved from
the MLS also exhibited strong stratospheric SO2 enhancements to an
altitude of nearly 63,000 feet, or approximately 19 kilometers. Hence,
the SO2 profile data corroborate the high injection heights suggested
by the combined OMI/MODIS imagery. Additionally, a back trajectory
launched from a June 19 MLS SO2 observation shows that the
stratospheric SO2 plume moves from the Mideast and Africa through
mid-latitude Asia to the Pacific Ocean, never encountering the Asian
Monsoon - a progression consistent with the region's recorded prevailing
winds.
These data convincingly show a classic Plinian characterization of the
Nabro June 13 eruption defined by volcanic aerosols and other gases
being injected into the stratosphere.
Received on Sat Feb 09 2013 - 10:36:51 EST
