How do stratospheric sulfate and meteoritic aerosols affect cirrus clouds and PSCs and their dehydration potential?

Tuesday, 20 March 2018
Iriarte (Hotel Botanico)
Beiping Luo1, Lamont R Poole2, Michael C Pitts3 and Thomas Peter1, (1)ETH Swiss Federal Institute of Technology Zurich, Institute for Atmosphere and Climate Science, Zurich, Switzerland, (2)Science Systems and Applications, Inc., Hampton, VA, United States, (3)NASA Langley Research Center, Hampton, VA, United States
Abstract:

Ice may nucleate homogeneously or heterogeneously in aerosol particles. While ice in polar stratospheric clouds (PSCs) downstream of mountain waves forms homogeneously in aqueous sulfuric acid droplets, synoptic ice particles form heterogeneously, most likely on meteoritic smoke particles (MSPs). Based on CALIPSO PSC observations during the Arctic winter 2009/2010, meteoritic dust is suspected to contain particularly good ice nucleating particles (INPs). For Antarctic winters, we investigate the effect of volcanically changing sulfate amounts on wave ice formation. By means of microphysical modeling, the nucleation properties of MSPs are revisited using WACCM-simulated MSPs and CALISPO observations of synoptic ice PSCs, and their dehydration potential is evaluated.

The stratospheric sulfate and meteoritic aerosols enter troposphere by sedimentation and inmixing of subsiding stratospheric air. Instruments on satellites, aircraft and balloons observed optically very thin clouds with low number density of ice particles. Our simulations suggest that heterogeneous ice nucleation on MSPs can explain the observed low number density of cirrus clouds in the tropopause region. Simulated backscatter ratios of heterogeneous agree well with observations. The low number density leads to large ice particles and a corresponding large dehydration potential, and play an important role for the water mixing ratio entering the stratosphere.

MSPs are prime candidates for cirrus ice nucleation in the tropopause regions, possibly rivalled by glassy organic particles. To characterize the chemical and physical state of INPs in the tropopause region will require further studies.

<< Previous Abstract | Next Abstract >>