Sensitivity of Numerical Simulation of Early Rapid Intensification of Hurricane Emily (2005) to Cloud Microphysical and Planetary Boundary Layer Parameterizations

Abstract

An advanced research version of the Weather Research and Forecasting (ARW) Model is used to simulate the early rapid intensification of Hurricane Emily (2005) using grids nested to high resolution (3 km). A series of numerical simulations is conducted to examine the sensitivity of the simulation to available cloud microphysical (CM) and planetary boundary layer (PBL) parameterization schemes. Results indicate that the numerical simulations of the early rapid intensification of Hurricane Emily are very sensitive to the choice of CM and PBL schemes in the ARW model. Specifically, with different CM schemes, the simulated minimum central sea level pressure (MSLP) varies by up to 29 hPa, and the use of various PBL schemes has resulted in differences in the simulated MSLP of up to 19 hPa during the 30-h forecast period. Physical processes associated with the above sensitivities are investigated. It is found that the magnitude of the environmental vertical wind shear is not well correlated with simulated hurricane intensities. In contrast, the eyewall convective heating distributions and the latent heat flux and high equivalent potential temperature ( e ) feeding from the ocean surface are directly associated with the simulated intensities. Consistent with recognized facts, higher latent heat release in stronger eyewall convection, stronger surface energy, and high e air feeding from the ocean surface into the hurricane eyewall are evident in the more enhanced convection and intense storms. The sensitivity studies in this paper also indicate that the contributions from the CM and PBL processes can only partially explain the slow intensification in the ARW simulations. Simulation at 1-km grid resolution shows a slight improvement in Emily's intensity forecast, implying that the higher resolution is somewhat helpful, but still not enough to cause the model to reproduce the real intensity of the hurricane.

Sensitivity of Numerical Simulations of the Early Rapid Intensification of Hurricane Emily to Cumulus Parameterization Schemes in Different Model Horizontal Resolutions

“…Despite the results above, numerical simulation of Hurricane Emily's rapid intensification is also very sensitive to the choice of the microphysics schemes in WRF model (see detailed results in Li and Pu 2008). The signifi- cant sensitivity of numerical simulations of Emily's rapid intensification to various model physical options indicates the great importance of physical processes and the complications of the use of physical parameterization schemes in producing accurate numerical forecasts of hurricanes' intensity change.…”

“…3.5 Convective heating rate and inner core dynamic structure Hurricane intensity has a close relationship with the magnitude and structure of the latent heat release (Zhu and Zhang 2006;Li and Pu 2008). Figure 6 compares the distribution of the convective heating rate at 500 hPa from di¤erent experiments at 0000 UTC 16 July 2005.…”

“…Previous studies showed that the simulations of hurricane intensity and structure were influenced by physical processes in numerical models (Li and Pu 2008;McFarquhar et al 2006;Braun and Tao 2000), the interactions among the physical processes, as well as the model horizontal grid spacing (Liu et al 1997;Walsh and Watterson 1997;Karyampudi et al 1998;Davis and Bosart 2002).…”

“…Hence, the most rapid development of the storm was produced when evaporation processes are removed. In recent study, Li and Pu (2008) found that the numerical simulations of the early rapid intensification of Hurricane Emily (2005) are very sensitive to the choice of cloud microphysical scheme in the Weather Research and Forecasting (WRF) model. Specifically, with di¤er-ent cloud microphysical schemes, the simulated minimum central sea level pressure varies by up to 29 hPa.…”

Modeling Rapid Intensification of Typhoon Saomai (2006) with the Weather Research and Forecasting Model and Sensitivity to Cloud Microphysical Parameterizations

“…They showed that the condensation process in the cloud microphysical scheme had a major impact on the forecast of Erin's final intensity. Recently, Li and Pu (2008) conducted a series of numerical simulations to examine the sensitivity of the simulation to available cloud microphysical and PBL parameterization schemes. The results indicated that the numerical simulations of the early rapid intensification of Hurricane Emily are very sensitive to the choice of cloud microphysical and PBL schemes in the ARW model.…”