Dispersion of the Nabro volcanic plume and its relation to the Asian summer...

Fairlie, T. D., J. Jean-Paul, K. Bedka, et al. (2014), Dispersion of the Nabro volcanic plume and its relation to the Asian summer monsoon, Atmos. Chem. Phys., 14, 7045-7057, doi:10.5194/acp-14-7045-2014.

 We use nighttime measurements from the Cloud

Aerosol Lidar and Infrared Pathfinder Satellite Observation

(CALIPSO) satellite, together with a Lagrangian trajectory

model, to study the initial dispersion of volcanic aerosol

from the eruption of Mt. Nabro (Ethiopia/Eritrea) in June

2011. The Nabro eruption reached the upper troposphere and

lower stratosphere (UTLS) directly, and the plume was initially

entrained by the flow surrounding the Asian anticyclone,

which prevails in the UTLS from the Mediterranean

Sea to East Asia during boreal summer. CALIPSO detected

aerosol layers, with optical properties consistent with sulfate,

in the lower stratosphere above the monsoon convective

region in South and Southeast Asia within 10 days of the

eruption. We show that quasi-isentropic differential advection

in the vertically sheared flow surrounding the Asian anticyclone

explains many of these stratospheric aerosol layers.

We use Meteosat-7 data to examine the possible role of deep

convection in the Asian monsoon in transporting volcanic

material to the lower stratosphere during this time, but find

no evidence that convection played a direct role, in contrast

with claims made in earlier studies. On longer timescales, we

use CALIPSO data to illustrate diabatic ascent of the Nabro

aerosol in the lower stratosphere at rates of 10K per month

for the first two months after the eruption, falling to 3K

per month after the Asian anticyclone dissipates. Maps of

stratospheric aerosol optical depth (AOD) show local peaks

of 0.04–0.06 in July in the region of the Asian anticyclone;

we find associated estimates of radiative forcing small, 5–

10% of those reported for the eruption of Mt. Pinatubo in

1991. Additionally, we find no clear response in outgoing

shortwave (SW) flux due to the presence of Nabro aerosol

viewed in the context of SW flux variability as measured by

CERES (Clouds and Earth Radiant Energy System).

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Research Program: 
Atmospheric Composition Modeling and Analysis Program (ACMAP)