Steven A Rutledge — Colorado State University
Taka Iguchi — University of Maryland College Park
Toshihisa Matsui — Earth System Science Interdisciplinary Center at University of Maryland
Brenda Dolan — Colorado State University
Wei-Kuo Tao — NASA - Goddard Space Flight Center
Stephen Edward Lang — NASA - Goddard Space Flight Center
Julie Barnum — Colorado State University Department of Atmospheric Science
Category
Convective clouds, including aerosol interactions
Description
Time series for total, convective and stratiform areal averaged rain rates for the TWP-ICE base simulation (solid) and polluted simulation (dashed) using the WRF-SBM model.
In this work, we are performing numerical model simulations with the WRF-SBM to investigate how instability (CAPE) and CCN concentrations may impact deep convection. A spectral bin microphysical formulation is being employed to provide more detailed microphysical simulations. We have selected cases from both the tropics (derived from the TWP-ICE field campaign) and the mid-latitudes (derived from the MC3E field campaign). Representative CCN concentrations are dynamically downscaled from the NASA MERRA Aerosol Reanalysis to arrive at base CCN concentration inputs for the WRF model. Roughly speaking, peak CCN concentrations (SS=1%) for the base simulations are 100 cm-3 for TWP-ICE and 1500 cm-3 for MC3E. CCN sensitivity tests are performed by simply interchanging the tropical and mid-latitude CCN concentrations, feeding the TWP-ICE case with the mid-latitude CCN profile and vice versa. For the TWP-ICE case, a 10% increase in the areal-averaged convective rain rate is found when CCN concentrations are increased to mid-latitude values, which is approximately an order of magnitude increase in CCN. The convective component is characterized by larger graupel volumes in the “polluted” simulation compared to the base case, consistent with previous studies on convective invigoration by CCN. Convective rain rates are seriously reduced in the MC3E simulation when “clean” CCN profiles are used. Additionally, we also will report on the response to simultaneously modifying CAPE and CCN. The POLARRIS framework developed in the first part of this research will be utilized to compare polarimetric fields produced by the model for the base and CCN sensitivity simulations.
