Topic #6: Ice/liquid mass partitioning in mixed phase cloud Co-leaders Greg McFarquhar (in-situ) Johannes Bühl (remote sensing) Participants In-situ: Bundke, Esposito, Hamilton, Henneberger Johnson, Jourdan, Krämer, Lawson, Meyer, Minikin, Schwarzenboeck, Ulanowski Remote sensing: Alexander, Bieligk, Kommpula, Maahn, Wang Modeling: Flossman, Lohmann

1. General Description of Topic Theme and Objectives of the Topic Working Group From Baumgardner et al. (2012) 1.What is the definition of a mixed-phase cloud? What is minimum ratio of LWC/IWC required to identify cloud as mixed-phase 2.What are spatial scales of mixing between liquid & ice and how do they vary with height & meteorological conditions? 3.How are liquid & ice partitioned with respect to particle sizes (e.g., are all small particles liquid & all large particles ice) 4.How can small particles be distinguished from supercooled droplets & do frozen drops evolve in shape according to condition?

2. Brief Status of Topics 2.1 In-Situ – Review of material from 2010 workshop in attached slides 2.2 Remote Sensing – See following example 2.3 Modeling – Need info

Liquid vs. ice mass partitioning possible by combination of remote sensing and in- situ measurements  Cloud radars (like the Mira36) are most not sensitive to detect falling ice particles  Lidars are best in detecting liquid (sub)layers  Lidar/Radar depolarization and terminal fall speed can be used to further classify detected particles LWC and IWC as products of CLOUDNET  LWC: Scaled adiabatic Method (assisted by Radiometer)  IWC: Parametrization from In-Situ Measurements (Hogan 2006) Remote Sensing – Example Case

LidarRadar Signal Depolarization Fall Velocity

Remote Sensing – Example Case Liquid Water Content [kg/m^3] (CLOUDNET Scaled Adiabatic) Ice Water Content [kg/m^3] (Parametrization of Hogan et. al., 2006)

3. Progress in Last 3 years 3.1 In-Situ – McFarquhar et al. (2013) analysis of CPI images of small particles in mixed- phase clouds – Aerosol effects on mixed-phase clouds during ISDAC (Jackson et al. 2012) – Tethered balloon observations (Lawson et al. 2011; Sikand et al. 2013) – Dependence of vertical profiles on meteorology (e.g., shallow vs. synoptic clouds, Noh et al. 2013) 3.2 Remote Sensing – Dual polarization radar to discriminate phase (Plummer et al. 2010) – Radar doppler spectra (Luke et al. 2010; Verlinde et al. 2013) to detect supercooled water – Liao and Meneghini (2013) dielectric constants computed for oblate and prolate spheroids 3.3 Modeling – Studies of aerosol effects on models of mixed-phase clouds (Morrison et al. 2010; Zubler et al. 2011) – Influence of ice habit on glaciation and evolution (Sulia & Harrington 2011; Avramov and Harrington 2010) – Impact of aerosols on global modeling of mixed clouds (Storelvmo et al. 2011)

4. Remaining Unknowns and Uncertainties 4.1 In-Situ – Discrimination between water/ice for smallest hydrometeors still difficult – Elimination of shattered artifacts from probes still requires care and caution – Fine spatial resolution observations required to determine spatial scale of mixing – Observations in greater range of aerosol concentrations/compositions & meteorology 4.2 Remote Sensing – Definition of “mixed-phase cloud” still unclear – Estimation of IWC/TWC or IWP/TWP should be taken into account 4.3 Modeling