A044-0007
Uncertainty in aerosol limb measurements following the Raikoke eruption
Tuesday, 8 December 2020
Poster
Landon A Rieger1, Adam E Bourassa2, Daniel Zawada1, Doug A Degenstein2, Sergey M. Khaykin3 and Ghassan Taha4, (1)University of Saskatchewan, Saskatoon, SK, Canada, (2)University of Saskatchewan, Department of Physics & Engineering Physics, Saskatoon, SK, Canada, (3)LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales, LATMOS, Paris Cedex 05, France, (4)Universities Space Research Association, NASA/code 614, Greenbelt, MD, United States
Abstract:
The eruption of Raikoke on June 22
nd, 2019 was one of the largest in recent decades, spewing approximately 1.5 Tg of sulfur up to 17 km altitude. This eruption has been widely studied using a combination of climate models and measurement systems, including ground based lidars, in situ particle counters, and a variety of satellite platforms. The early plume has been well categorized by high-resolution measurements from CALIPSO, MODIS, VIIRS, IASI and other nadir viewing instruments, but as the plume ages investigation often shifts to limb sounding instruments that provide greater sensitivity to lower aerosol levels. These instruments have proven critical in understanding the long-term radiative and climatic impacts of stratospheric aerosol burdens after these explosive events, but the complexity of the measurements, sampling, and retrievals has made error characterization in high-loading conditions difficult.
This work explores the systematic biases in limb measurements after the Raikoke eruption due to a variety of factors often implicit in the retrievals. These include horizontal homogeneity, saturation during the early plume, and microphysical assumptions. This is investigated using OMPS-LP, OSIRIS and SAGE III limb sounders. OMPS and OSIRIS are both limb scattering instruments in the UV to NIR, providing measurements at different solar geometries that highlight the sensitivity to microphysical assumptions and satellite orbit. OMPS measurements can also be inverted using a tomographic technique, and, in conjunction with CALIPSO measurements, this is used to investigate errors in the retrieval due to horizontal inhomogeneity in the early plume. SAGE III measurements are further used to examine the difference in limb techniques in the UTLS region, where errors can be particularly large; as well as examine the biases inherent in lower sampling rates.
This work highlights the subtleties in comparing limb observations, with implications for model comparisons after large events such as volcanic eruptions and forest fires. Not only in the early plume, where sampling can be sparse, but also in the weeks and months following the eruption.
