Arctic stratospheric dehydration – Part 2: Microphysical modeling

Abstract

Abstract. Large areas of synoptic-scale ice PSCs (polar stratospheric clouds) distinguished the Arctic winter 2009/2010 from other years and revealed unprecedented evidence of water redistribution in the stratosphere. A unique snapshot of water vapor repartitioning into ice particles was obtained under extremely cold Arctic conditions with temperatures around 183 K. Balloon-borne, aircraft and satellitebased measurements suggest that synoptic-scale ice PSCs and concurrent reductions and enhancements in water vapor are tightly linked with the observed de-and rehydration signatures, respectively. In a companion paper (Part 1), water vapor and aerosol backscatter measurements from the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) and LAPBIAT-II (Lapland Atmosphere-Biosphere Facility) field campaigns have been analyzed in detail. This paper uses a column version of the Zurich Optical and Microphysical box Model (ZOMM) including newly developed NAT (nitric acid trihydrate) and ice nucleation parameterizations. Particle sedimentation is calculated in order to simulate the vertical redistribution of chemical species such as water and nitric acid. Despite limitations given by wind shear and uncertainties in the initial water vapor profile, the column modeling unequivocally shows that (1) accounting for small-scale temperature fluctuations along the trajectories is essential in order to reach agreement between simulated optical cloud properties and observations, and (2) the use of recently developed heterogeneous ice nucleation parameterizations allows the reproduction of the observed signatures of de-and rehydration. Conversely, the vertical redistribution of water measured cannot be explained in terms of homogeneous nucleation of ice clouds, whose particle radii remain too small to cause significant dehydration.

Accuracy and precision of polar lower stratospheric temperatures from reanalyses evaluated from A-Train CALIOP and MLS, COSMIC GPS RO, and the equilibrium thermodynamics of supercooled ternary solutions and ice clouds

“…Mesoscale temperature fluctuations have a significant effect on the formation of PSCs (Murphy and Gary, 1995;Dörn-brack and Leutbecher, 2001;Gary, 2006) and therefore the capability of models to accurately mimic PSC formation requires consideration of these sub-grid processes (Engel et al, 2014;Hoyle et al, 2013). The high vertical resolution of the COSMIC temperatures allows an examination of the spectrum of the temperature variance over the height region of PSC formation.…”

Pre-activation of aerosol particles by ice preserved in pores

“…Meteoritic material is mostly internally mixed with sulfuric acid (Murphy et al, 2007). Meteoritic particles have been considered as nucleating particles for nitric acid trihydrate (NAT) (Biermann et al, 1996;Voigt et al, 2005) and ice crystals (Engel et al, , 2014, but have not excelled as very efficient INPs in laboratory studies (Mason and Maybank, 1958;Biermann et al, 1996). However, some of them were susceptible to pre-activation (see Sect.…”

Lagrangian analysis of microphysical and chemical processes in the Antarctic stratosphere: a case study

“…So far, ZOMM has always been initiated under typical background conditions for the winter polar stratosphere Engel et al, 2013). The study by Engel et al (2014) was the first study that used the microphysical model as a column model for PSC simulations. For the present study, we developed the model further and introduced the possibility of prescribing a particle size distribution.…”

“…The sedimentation of PSC particles is accounted for by using the column version of ZOMM as described in Engel et al (2014). So far, ZOMM has always been initiated under typical background conditions for the winter polar stratosphere Engel et al, 2013).…”