Investigation of Droplet Size Distributions and Drizzle Formation Using A New Trajectory Ensemble Model. Part II: Lucky Parcels

Abstract A novel trajectory ensemble model of the cloud-topped boundary layer containing 1340 Lagrangian parcels moving with a turbulent-like flow with the observed statistical properties was applied to investigate the formation of the microphysical structure of stratocumulus clouds (Sc) in a nonmixing limit (when turbulent mixing between the parcels is not taken into account). The Sc observed in two research flights during the Second Dynamics and Chemistry of the Marine Stratocumulus field study (DYCOMS II)—RF01 (no drizzle) and RF07 (weak drizzle)—are simulated. The mechanisms leading to a high variability of droplet size distributions (DSDs) with different spectrum width and dispersion are discussed. Drizzle formation was investigated using the radar reflectivity–LWC and LWC–effective drop radius diagrams simulated by the model in the nondrizzle and drizzle cases. It is shown that in the RF07 case large cloud droplets that trigger drop collisions and drizzle formation form only in a small fraction (abo...

[1]  W. Cotton,et al.  Radiative impacts on the growth of a population of drops within simulated summertime Arctic stratus , 2000 .

[2]  S. Kreidenweis,et al.  Stratocumulus processing of gases and cloud condensation nuclei: 1. Trajectory ensemble model , 1998 .

[3]  James G. Hudson,et al.  Maritime/continental microphysical contrasts in stratus , 2002 .

[4]  Mark Pinsky,et al.  Notes on the state-of-the-art numerical modeling of cloud microphysics , 2000 .

[5]  C. Bretherton,et al.  An intercomparison of radiatively driven entrainment and turbulence in a smoke cloud, as simulated by different numerical models , 1996 .

[6]  M. Khairoutdinov,et al.  A New Cloud Physics Parameterization in a Large-Eddy Simulation Model of Marine Stratocumulus , 2000 .

[7]  A. Pokrovsky,et al.  Simulation of effects of atmospheric aerosols on deep turbulent convective clouds using a spectral microphysics mixed-phase cumulus cloud model. Part I: Model description and possible applications , 2004 .

[8]  B. Albrecht.  Aerosols, Cloud Microphysics, and Fractional Cloudiness , 1989, Science.

[9]  Manfred Wendisch,et al.  Wind Tunnel Tests of the Airborne PVM-100A Response to Large Droplets , 2002 .

[10]  B. Stevens,et al.  Observations of Drizzle in Nocturnal Marine Stratocumulus , 2005 .

[11]  S. Twomey.  The Influence of Pollution on the Shortwave Albedo of Clouds , 1977 .

[12]  B. Stevens,et al.  Elements of the microphysical structure of numerically simulated nonprecipitating stratocumulus , 1996 .

[13]  K. Bryan.  A SCHEME FOR NUMERICAL INTEGRATION OF THE EQUATIONS OF MOTION ON AN IRREGULAR GRID FREE OF NONLINEAR INSTABILITY , 1966 .

[14]  Hanna Pawlowska,et al.  An observational study of drizzle formation in stratocumulus clouds for general circulation model (GCM) parameterizations , 2003 .

[15]  L. Schüller,et al.  Radiative Properties of Boundary Layer Clouds: Droplet Effective Radius versus Number Concentration , 2000 .

[16]  A. Korolev,et al.  The Influence of Supersaturation Fluctuations on Droplet Size Spectra Formation , 1995 .

[17]  D. Lenschow,et al.  Turbulence measurements in marine stratocumulus with airborne Doppler radar , 2005 .

[18]  D. Lilly,et al.  The effect of CCN regeneration on the evolution of stratocumulus cloud layers , 1994 .

[19]  C. Bretherton,et al.  Evaluation of Large-Eddy Simulations via Observations of Nocturnal Marine Stratocumulus , 2005 .

[20]  M. Shapiro,et al.  Collision Efficiency of Drops in a Wide Range of Reynolds Numbers: Effects of Pressure on Spectrum Evolution , 2001 .

[21]  A. Bott.  A positive definite advection scheme obtained by nonlinear renormalization of the advective fluxes , 1989 .

[22]  B. Stevens,et al.  Accumulation mode aerosol, pockets of open cells, and particle nucleation in the remote subtropical Pacific marine boundary layer , 2006 .

[23]  B. Stevens,et al.  Observations of Entrainment in Eastern Pacific Marine Stratocumulus Using Three Conserved Scalars , 2005 .

[24]  H. Gerber,et al.  Microphysics of Marine Stratocumulus Clouds with Two Drizzle Modes , 1996 .

[25]  C. Bretherton,et al.  POCKETS OF OPEN CELLS AND DRIZZLE IN MARINE STRATOCUMULUS , 2004 .

[26]  A. Khain,et al.  The effect of wind velocity fluctuations on drop spectrum broadening in stratocumulus clouds , 2005 .

[27]  Margaret A. LeMone,et al.  The Structure and Dynamics of Horizontal Roll Vortices in the Planetary Boundary Layer , 1973 .

[28]  Wojciech W. Grabowski,et al.  Observations of the width of cloud droplet spectra in stratocumulus , 2006 .

[29]  W. Cotton,et al.  The Relationship between Drop In-Cloud Residence Time and Drizzle Production in Numerically Simulated Stratocumulus Clouds , 1996 .

[30]  D. W. Johnson,et al.  The Measurement and Parameterization of Effective Radius of Droplets in Warm Stratocumulus Clouds , 1994 .

[31]  Alexander Khain,et al.  Effects of in‐cloud nucleation and turbulence on droplet spectrum formation in cumulus clouds , 2002 .

[32]  S. Nicholls.  The dynamics of stratocumulus: Aircraft observations and comparisons with a mixed layer model , 1984 .

[33]  B. Stevens,et al.  A critique of one- and two-dimensional models of boundary layer clouds with a binned representations of drop microphysics , 1998 .

[34]  A. Korolev,et al.  The Nevzorov Airborne Hot-Wire LWC-TWC Probe: Principle of Operation and Performance Characteristics , 1998 .

[35]  B. Stevens,et al.  Simulations of marine stratocumulus using a new microphysical parameterization scheme , 1998 .

[36]  B. Stevens,et al.  Large-Eddy Simulations of Strongly Precipitating, Shallow, Stratocumulus-Topped Boundary Layers , 1998 .

[37]  A. Sterkin,et al.  Investigation of Droplet Size Distributions and Drizzle Formation Using a New Trajectory Ensemble Model. Part I: Model Description and First Results in a Nonmixing Limit , 2008 .

[38]  Andreas Bott,et al.  A Flux Method for the Numerical Solution of the Stochastic Collection Equation , 1998 .

[39]  Rosenfeld,et al.  Suppression of rain and snow by urban and industrial air pollution , 2000, Science.

[40]  B. Stevens,et al.  Large-Eddy Simulations of Radiatively Driven Convection: Sensitivities to the Representation of Small Scales , 1999 .

[41]  M. Khairoutdinov,et al.  A Large Eddy Simulation Model with Explicit Microphysics: Validation against Aircraft Observations of a Stratocumulus-Topped Boundary Layer , 1999 .

[42]  H. Russchenberg,et al.  Combined Observational and Model Investigations of the Z–LWC Relationship in Stratocumulus Clouds , 2008 .

[43]  D. Lilly,et al.  Dynamics and chemistry of marine stratocumulus - DYCOMS II , 2003 .

[44]  B. Stevens,et al.  An explicit cloud microphysics/LES model designed to simulate the Twomey effect , 1994 .

[45]  A. Korolev.  A study of bimodal droplet size distributions in stratiform clouds , 1994 .

[46]  M. Andreae,et al.  Smoking Rain Clouds over the Amazon , 2004, Science.

[47]  D. Randall,et al.  Cloud resolving modeling of the ARM summer 1997 IOP: Model formulation, results, uncertainties, and sensitivities , 2003 .

[48]  R. Wood,et al.  Drizzle in Stratiform Boundary Layer Clouds. Part I: Vertical and Horizontal Structure , 2005 .

[49]  D. Lilly,et al.  On entrainment rates in nocturnal marine stratocumulus , 2003 .

[50]  J.J.M. de Wit,et al.  Estimating effective radius and liquid water content from radar and lidar based on the CLARE98 data-set , 2000 .

[51]  Melanie A. Wetzel,et al.  Evaluation of the aerosol indirect effect in marine stratocumulus clouds : droplet number, size, liquid water path, and radiative impact , 2005 .

[52]  Oleg A. Krasnov,et al.  An enhanced algorithm for the retrieval of liquid water cloud properties from simultaneous radar and lidar measurements. Part I: The basic analysis of in situ measured drop size spectra , 2002 .

[53]  Zones of increased and decreased droplet concentration in stratiform clouds , 1993 .

[54]  A. Khain,et al.  Thermodynamic factors influencing bimodal spectrum formation in cumulus clouds , 2003 .

[55]  D. Lilly,et al.  Modeling of Stratocumulus Cloud Layers in a Large Eddy Simulation Model with Explicit Microphysics. , 1995 .

[56]  A. S. Monin,et al.  Statistical Fluid Mechanics: The Mechanics of Turbulence , 1998 .