Topic #6: Ice/liquid mass partitioning in mixed phase cloud

Co-leadersGreg McFarquhar (in-situ)

Johannes Bühl (remote sensing)

ParticipantsIn-situ: Bundke, Esposito, Hamilton, Henneberger Johnson, Jourdan, Krämer, Lawson, Meyer, Minikin, Schwarzenboeck, Ulanowski Remote sensing: Alexander, Bieligk, Kommpula, Maahn, WangModeling: 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

Remote Sensing – Example Case Lidar Radar

Signal

Depolarization

Fall Velocity

Remote Sensing – Example Case

Liquid Water Content [kg/m^3](CLOUDNET Scaled Adiabatic)

Ice Water Content [kg/m^3](Parametrization ofHogan 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