A Conceptual Model for the Hydrometeor Structure of Mesoscale Convective Systems during the MJO Active Stage Hannah C. Barnes Robert A. Houze, Jr. University of Washington 31 st Conference on Hurricanes and Tropical Meteorology Town & Country Resort and Conference Center, San Diego, CA 2 April 2014 Funded by NSF –Grant AGS and DOE Grant DE-SC

Objective Characterize hydrometeor structure of MCSs Composite with respect to kinematic structure

Kinematic Structure of Mesoscale Convective Systems (MCSs) ConvectiveStratiform Moncrieff (1992): Layer airflow Kingsmill and Houze (1999): 3D structure

Addu Atoll Dual wavelength – Only using S-Band Single Doppler Dual-polarimetric – Particle Identification Algorithm (Vivekanandan et al., 1999) RHI sector and within 100 km NCAR SPolKa Radar

Case Selection SPolKa data during active phases Subjectively identify cases SPolKa radial velocity Layer lifting One per storm 25 Convective Cases 37 Stratiform Cases Convective: 24 Oct 2011 Stratiform: 23 December 2011 dBZ V r profile dBZ

Composite Structure X Scale Factor Z Scale Factor Radar Data 1.) Map kinematics and hydrometeors using radial velocity and PID 2.) Composite around layer lifting model Compositing Methodology

Heavy RainModerate RainLight Rain Graupel Rimed Aggregates Wet Aggregates Dry Aggregates Small Ice Crystals Horz. Oriented Ice Convective Updraft Composites

Dry Aggregates Graupel/Rimed Aggregates Heavy Rain Wet AggregatesModerate Rain Small Ice Crystals Light Rain Hydrometeor Organization in Convective Updrafts

Stratiform Stratiform with leading lineStratiform without leading line 23 December November 2011 dBZ

Stratiform with Leading Line Composites Heavy Rain Moderate RainLight Rain Graupel Rimed Aggregates Wet AggregatesDry Aggregates Small Ice Crystals Horz. Oriented Ice

Stratiform without Leading Line Composites Heavy Rain Light RainModerate Rain Graupel Rimed Aggregates Wet AggregatesDry AggregatesSmall Ice CrystalsHorz. Oriented Ice

Light Rain Graupel / Rimed Aggregates Wet Aggregates Horizontally Oriented Ice Dry Aggregates Small Ice Crystals 0˚C Moderate Rain Heavy Rain Hydrometeor Organization in Stratiform

Conclusions Hydrometeor organization consistent across MCS types Heating similar with and without leading line Interpretation of microphysical processes Comparison of model output and radar observations ConvectiveStratiform

Frequency of Occurrence Convective Updraft Inflow Stratiform with Leading Line Stratiform without Leading Line Graupel/Rimed Aggregates88%66%64% Heavy Rain92%11%14% Moderate Rain100%55%60% Light Rain72%100% Wet Aggregates92%100% Dry Aggregates100% Small Ice Crystals92%100%89% Horizontally-Oriented Ice Crystals 20%44%53%

Areal Coverage Convective Updraft Inflow Stratiform with Leading Line Stratiform without Leading Line Graupel/Rimed Aggregates2%0.3%0.5% Heavy Rain12%4%1% Moderate Rain16%5%6% Light Rain13%28%31% Wet Aggregates3%1%4% Dry Aggregates22%12%18% Small Ice Crystals12%26%18% Horizontally-Oriented Ice Crystals -2%

Distribution of Convective Polarimetric Variables Reflectivity Differential Reflectivity Temperature Linear Differential Reflectivity Correlation Coefficient Differential Reflectivity Specific Differential Phase GA HR MR LR WA DA SI HI

Distribution of Mid-Level Polarimetric Variables Reflectivity Temperature Linear Differential Reflectivity Correlation Coefficient Differential Reflectivity Specific Differential Phase GA HR MR LR WA DA SI HI

Confidence of PID PID interest value Likelihood of particle type Highest interest value chosen PID confidence Difference of 1 st and 2 nd largest interest values Larger difference = more confidence Convective Updraft Mid-Level Inflow with Leading Line

Mesoscale Modeling of Squall Line WRF Resolution: Outer – 9km, Inner – 3km Cu Param: Outer – KF, Inner – None MP Param: Both - Goddard PBL Param: Both – UW Forcing: ERAi 00 UTC 23 Dec – 00 UTC 25 Dec Reflectivity Zonal Wind

Distribution of Hydrometeor Mixing Ratio Zonal Wind and Reflectivity Rain Mixing Ratio Snow Mixing Ratio Cloud Mixing Ratio Graupel Mixing Ratio Ice Mixing Ratio

Convective Example Oct 24

Squall Example Nov 18

Differences in Graupel/Rimed Aggregates and Wet Aggregates in Mid-Level Inflow Cases Graupel Wet Aggregates Only