Aerosol and CAPE Sensitivity Simulations with the NASA WRF bin microphysical model
Poster PDF
Authors
Steven A Rutledge — Colorado State University
Taka Iguchi — University of Maryland College Park
Wei-Kuo Tao — NASA - Goddard Space Flight Center
Toshihisa Matsui — Earth System Science Interdisciplinary Center at University of Maryland
Brenda Dolan — Colorado State University
Stephen Edward Lang — NASA - Goddard Space Flight Center
Julie Barnum — Colorado State University Department of Atmospheric Science
Category
Convective clouds, including aerosol interactions
Description
Systematic sensitivity experiments were configured to investigate the effects of cloud condensation nuclei (CCN) loading on deep convective systems in tropical maritime and mid-latitude continental conditions. A new approach was adopted to change aerosol fields of two different cases (tropical and mid-latitude) in the framework of aerosol dynamical downscaling derived from large-scale aerosol simulations. The NASA WRF model using bin microphysics (SBM) was used for both control and a series of sensitivity simulations. For the mid-latitude simulation, we systematically decreased CCN concentrations and CAPE from the control run. For the tropical simulation, we systematically increased CCN concentrations and decreased CAPE compared to the control run. For both the mid-latitude and tropical cases, the accumulated surface precipitation was found to monotonically increase with CCN concentration. As expected, when CAPE decreased, accumulated surface precipitation decreased, somewhat independent of CCN concentration. For the mid-latitude simulation, supercooled liquid water increased with increasing CCN, leading to more hail production aloft. Hail formed at the expense of graupel. The large number of aerosol sensitivity experiments with the SBM are summarized in a conceptual model that explains increasing/decreasing trends of each hydrometeor type (ice, snow, graupel, hail, rain, etc), convective-stratiform precipitation rates, and the areal fractions of convective and stratiform rain. This conceptual model provides insights regarding the complex aerosol and thermodynamic impacts on convective systems in continental and maritime environments.
