Aircraft and satellite based studies of stratospheric aerosol – composition, sources and climate forcing

Monday, 19 March 2018
Iriarte (Hotel Botanico)
Johan Friberg, Lund University, Lund University, Lund, Sweden, Bengt G Martinsson, Lund University, Lund, Sweden, Oscar S. Sandvik, Lund University, Physics, Lund, Sweden, Sandra M. Andersson, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden, Markus Hermann, Leibniz Institute for Tropospheric Research, Leipzig, Germany, Peter F. J. van Velthoven, Royal Netherlands Meteorological Institute, De Bilt, Netherlands and Andreas Zahn, Karlsruhe Institute of Technology, Karlsruhe, Germany
Abstract:
We use IAGOS-CARIBIC (aircraft) aerosol data together with the CALIOP satellite observations to study the stratosphere and upper troposphere (UT) in terms of aerosol optical depth (AOD), aerosol composition, aerosol sources, and transport pathways within, to, and from the stratosphere. The aerosol loads in the UT and lowermost stratosphere (LMS) are difficult to study and especially that in the extra-tropical tropopause layer (ExTL). There, the CARIBIC aircraft provides aerosol data since 1999, including concentrations of ~10 chemical elements (S, C, O, Fe, K, Ni etc.), e.g. revealing that organics constitute a significant fraction of stratospheric and UT aerosol (Friberg et al., 2014) as well as of volcanic aerosol (Martinsson et al., 2009). Recent studies based on photometer and CALIOP/CARIBIC data revealed that the LMS holds a significant fraction of the stratospheric AOD.

Particulate sulfur (S) measurements from CARIBIC were used to estimate the AOD of the lowest 3 km of the northern midlatitude LMS (Martinsson et al., 2017). A large portion of the UT aerosol was found to be of stratospheric origin. That portion was high (low) in spring (fall), and increased when the stratosphere was volcanically influenced. In fall, the Asian summer monsoon affected the S loading of the UT by providing a pool of aerosol in the stratosphere (ATAL) that was gradually subsiding to the UT.

Using CALIOP data, improving and extending the analyses by Andersson et al., (2015), we find volcanic aerosol down to the dynamical tropopause, here defined by a potential vorticity of 1.5 PVU (which is more than 1 km below the static tropopause). Furthermore, methods were developed to filter out polar stratospheric clouds and to correct for particle extinction that attenuated the backscattered laser signal in months following volcanic eruptions of Kasatochi (2008), Sarychev (2009), Nabro (2011) and Calbuco (2015). We present various projections and views of the stratospheric aerosol and estimate its AOD and radiative forcing in the period 2006 – 2015.

Andersson et al. (2015), doi:10.1038/ncomms8692

Friberg et al. (2014), doi:10.3402/tellusb.v66.23428

Martinsson et al. (2009), doi:0.1029/2009GL038735

Martinsson et al. (2017), doi:10.5194/acp-17-10937-2017

<< Previous Abstract | Next Abstract >>