Numerical Simulation of Hurricane Bonnie (1998). Part II: Sensitivity to Varying Cloud Microphysical Processes

In this study, the effects of various cloud microphysics processes on the hurricane intensity, precipitation, and inner-core structures are examined with a series of 5-day explicit simulations of Hurricane Bonnie (1998), using the results presented in Part I as a control run. It is found that varying cloud microphysics processes produces little sensitivity in hurricane track, except for very weak and shallow storms, but it produces pronounced departures in hurricane intensity and inner-core structures. Specifically, removing ice microphysics produces the weakest (15-hPa underdeepening) and shallowest storm with widespread cloud water but little rainwater in the upper troposphere. Removing graupel from the control run generates a weaker hurricane with a wider area of precipitation and more cloud coverage in the eyewall due to the enhanced horizontal advection of hydrometeors relative to the vertical fallouts (or increased water loading). Turning off the evaporation of cloud water and rainwater leads to the most rapid deepening storm (i.e., 90 hPa in 48 h) with the smallest radius but a wider eyewall and the strongest eyewall updrafts. The second strongest storm, but with the most amount of rainfall, is obtained when the melting effect is ignored. It is found that the cooling due to melting is more pronounced in the eyewall where more frozen hydrometeors, especially graupel, are available, whereas the evaporative cooling occurs more markedly when the storm environment is more unsaturated. It is shown that stronger storms tend to show more compact eyewalls with heavier precipitation and more symmetric structures in the warm-cored eye and in the eyewall. It is also shown that although the eyewall replacement scenarios occur as the simulated storms move into weak-sheared environments, the associated inner-core structural changes, timing, and location differ markedly, depending on the hurricane intensity. That is, the eyewall convection in weak storms tends to diminish shortly after being encircled by an outer rainband, whereas both the cloud band and the inner eyewall in strong storms tend to merge to form a new eyewall with a larger radius. The results indicate the importance of the Bergeron processes, including the growth and rapid fallout of graupel in the eyewall, and the latent heat of fusion in determining the intensity and inner-core structures of hurricanes, and the vulnerability of weak storms to the influence of large-scale sheared flows in terms of track, inner-core structures, and intensity changes.

[1]  Da‐Lin Zhang,et al.  A Multiscale Numerical Study of Hurricane Andrew (1992). Part II: Kinematics and Inner-Core Structures , 1999 .

[2]  Joanne Simpson,et al.  Comparison of Ice-Phase Microphysical Parameterization Schemes Using Numerical Simulations of Tropical Convection , 1991 .

[3]  Tong Zhu,et al.  Numerical Simulation of Hurricane Bonnie (1998). Part I: Eyewall Evolution and Intensity Changes , 2004 .

[4]  J. Dudhia.  A Nonhydrostatic Version of the Penn State–NCAR Mesoscale Model: Validation Tests and Simulation of an Atlantic Cyclone and Cold Front , 1993 .

[5]  Frank J. Wentz,et al.  Satellite microwave SST observations of transequatorial tropical instability waves , 2000 .

[6]  Robert A. Houze,et al.  Melting and Evaporation of Hydrometeors in Precipitation from the Anvil Clouds of Deep Tropical Convection , 1979 .

[7]  Yuqing Wang.  An explicit simulation of tropical cyclones with a triply nested movable mesh primitive equation model: TCM3. Part I: Model description and control experiment , 2001 .

[8]  S. Penner.  Melting and evaporation as rate processes. , 1948, The Journal of physical and colloid chemistry.

[9]  Hugh E. Willoughby,et al.  A Numerical Study of the Impact of Vertical Shear on the Distribution of Rainfall in Hurricane Bonnie (1998) , 2003 .

[10]  G. Grell,et al.  A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5) , 1994 .

[11]  H. Willoughby.  A Possible Mechanism for the Formation of Hurricane Rainbands , 1978 .

[12]  S. L. Rosenthal.  Numerical Simulation of Tropical Cyclone Development with Latent Heat Release by the Resolvable Scales I: Model Description and Preliminary Results , 1978 .

[13]  Hugh E. Willoughby,et al.  Concentric Eye Walls, Secondary Wind Maxima, and The Evolution of the Hurricane vortex , 1982 .

[14]  Da‐Lin Zhang,et al.  A Multiscale Numerical Study of Hurricane Andrew (1992). Part III: Dynamically Induced Vertical Motion , 2000 .

[15]  E. Zipser.  The Role of Organized Unsaturated Convective Downdrafts in the Structure and Rapid Decay of an Equatorial Disturbance , 1969 .

[16]  John M. Brown.  Mesoscale Unsaturated Downdrafts Driven by Rainfall Evaporation: A Numerical Study , 1979 .

[17]  S. Lord,et al.  Hurricane structure and evolution as simulated by an axisymmetric, nonhydrostatic numerical model , 1984 .

[18]  Tetsuya Theodore. Fujita,et al.  PRECIPITATION AND COLD AIR PRODUCTION IN MESOSCALE THUNDERSTORM SYSTEMS , 1959 .

[19]  Joanne Simpson,et al.  Goddard Cumulus Ensemble Model. Part I: Model Description , 1993 .

[20]  Yubao Liu,et al.  A Multiscale Numerical Study of Hurricane Andrew (1992). Part I: Explicit Simulation and Verification , 1997 .

[21]  J. Kain,et al.  Comments on “Parameterization of Convective Precipitation in Mesoscale Numerical Models: A Critical Review” , 1994 .

[22]  Da‐Lin Zhang,et al.  Impact of the Advanced Microwave Sounding Unit Measurements on Hurricane Prediction , 2002 .

[23]  Scott A. Braun,et al.  Sensitivity of High-Resolution Simulations of Hurricane Bob (1991) to Planetary Boundary Layer Parameterizations , 2000 .

[24]  Da‐Lin Zhang,et al.  A High-Resolution Model of the Planetary Boundary Layer—Sensitivity Tests and Comparisons with SESAME-79 Data , 1982 .

[25]  M. Yamasaki.  A Preliminary Experiment of the Tropical Cyclone without Parameterizing the Effects of Cumulus Convection , 1977 .

[26]  R. Simpson,et al.  Experimental cumulus dynamics. , 1965 .

[27]  Da‐Lin Zhang,et al.  Numerical sensitivity experiments of varying model physics on the structure, evolution and dynamics of two mesoscale convective systems , 1988 .

[28]  Da‐Lin Zhang,et al.  Numerical Simulation of an Intense Squall Line during 10–11 June 1985 PRE-STORM. Part II: Rear Inflow, Surface Pressure Perturbations and Stratiform Precipitation , 1989 .

[29]  M. Montgomery,et al.  A theory for vortex rossby‐waves and its application to spiral bands and intensity changes in hurricanes , 1997 .

[30]  Da‐Lin Zhang,et al.  A Multiscale Numerical Study of Hurricane Andrew (1992). Part VI: Small-Scale Inner-Core Structures and Wind Streaks , 2004 .

[31]  Stephen J. Lord,et al.  Role of a Parameterized Ice-Phase Microphysics in an Axisymmetric, Nonhydrostatic Tropical Cyclone Model , 1984 .

[32]  Yong Wang,et al.  An Explicit Simulation of Tropical Cyclones with a Triply Nested Movable Mesh Primitive Equation Model: TCM3. Part II: Model Refinements and Sensitivity to Cloud Microphysics Parameterization* , 2002 .