Aerosol Effects on Intensity of Landfalling Hurricanes as Seen from Simulations with the WRF Model with Spectral Bin Microphysics

• DOI: 10.1175/2009jas3210.1
• Publication Date: 2009-08-17T19:09:29Z
• Authors: A. Khain; B. Lynn; J. Dudhia
• Keywords: Graupel; Landfall; Intensity; Rainband

Abstract The evolution of a superhurricane (Katrina, August 2005) was simulated using the Weather Research and Forecasting Model (WRF; version 3.1) with explicit (nonparameterized) spectral bin microphysics (SBM). new computationally efficient microphysical scheme (FAST-SBM) implemented to WRF calculates at each time step in grid point size distributions atmospheric aerosols, water drops, cloud ice (ice crystals aggregates), graupel/hail. tropical cyclone (TC) during 72 h, beginning its bypassing Florida coast (27 landfall just east New Orleans, Louisiana (near end 29 August). WRF/SBM used investigate potential impact aerosols ingested into Katrina’s circulation passage through Gulf Mexico on structure intensity. It is shown that continental invigorated convection largely TC periphery, which led weakening prior landfall. Maximum took place ∼24 h before landfall, after intensity had reached maximum. minimum pressure increased by ∼15 hPa, maximum velocity decreased up 15 m s−1. Thus, model results indicate existence another (in addition decrease surface fluxes) mechanism TCs approaching land. This related effects involved circulation. substantially affect spatial distribution cloudiness hydrometeor contents. lightning within calculated compared Katrina. physical mechanisms aerosol-induced are discussed.