Assessing the Impacts of Different WRF Precipitation Physics in Hurricane Simulations

Abstract

Numerical weather prediction models play a major role in weather forecasting, especially in cases of extreme events. The Weather Research and Forecasting Model (WRF), among others, is extensively used for both research and practical applications. Previous studies have highlighted the sensitivity of this model to microphysics and cumulus schemes. This study investigated the performance of the WRF in forecasting precipitation, hurricane track, and landfall time using various microphysics and cumulus schemes. A total of 20 combinations of microphysics and cumulus schemes were used, and the model outputs were validated against ground-based observations. While the choice of microphysics and cumulus schemes can significantly impact model output, it is not the case that any single combination can be considered ''ideal'' for modeling all characteristics of a hurricane, including precipitation amount, areal extent, hurricane track, and the time of landfall. For example, the model's ability to simulate precipitation (with the least total bias) is best achieved using Betts-Miller-Janjić (BMJ) cumulus parameterization in combination with the WRF single-moment five-class microphysics scheme (WSM5). It was determined that the WSM5-BMJ, WSM3 (the three-class version of the WSM scheme)-BMJ, and Ferrier microphysics in combination with the Grell-Devenyi cumulus scheme were the best combinations for simulation of the landfall time. However, the hurricane track was best estimated using the Lin et al. and Kessler microphysics options with BMJ cumulus parameterization. Contrary to previous studies, these results indicated that the use of cumulus schemes improves model outputs when the grid size is smaller than 10 km. However, it was found that many of the differences between parameterization schemes may be well within the uncertainty of the measurements.

Influence of physics parameterization schemes on the simulation of a tropical-like cyclone in the Mediterranean Sea

“…about 50 km north of the actual location on the Ionian Sea (bold point), thus anticipating on average its evolution by about 1 h (see Table 3). Also, a simple, warm scheme, as Kessler (run mp1), is able to reproduce properly the minimum intensity and the track, in agreement with previous results on tropical cyclones (Li and Pu, 2008;Nasrollahi et al, 2012).…”

“…In particular, a few simulations miss the evolution into a tropicallike cyclone, since the vortex evolves into a symmetric structure, but whose warm core is confined only to the lower troposphere; on the other hand, experiments with simple schemes based on warm cloud processes, as Kessler, are skillful. The large sensitivity to microphysics is not surprising and common to tropical cyclone simulations (Zhu and Zhang, 2006;Li and Pu, 2008;Nasrollahi et al, 2012). It is known that many fundamental problems in cloud microphysics are still unsolved, and the lack of in-situ observations makes any progress very slow and difficult; also, most of the current parameterization schemes have been designed, applied and tested for stratiform clouds only, while processes important in deep convection are currently neglected, or not well represented (Seifert, 2006).…”

Effects of various combinations of boundary layer schemes and microphysics schemes on the track forecasts of tropical cyclones over the South China Sea

“…Studies have found that it can be effectively improved by some techniques, including ''optimizing'' the initial conditions through data assimilation (Zhou et al 2010;Zhang et al 2013;Zheng et al 2015), increasing the model resolution (De Bruijn and Brandsma 2000;Lonfat et al 2007), and adopting a ''best'' cumulus parameterization scheme that takes into account the specific region and model resolution (Nasrollahi et al 2012;Ma and Tan 2009). …”

Tracking a tropical cyclone through WRF–ARW simulation and sensitivity of model physics

“…Microphysics schemes are important in regional weather models for providing atmospheric heat and moisture tendencies (Nasrollahi et al 2012). Vertical flux of cloud, precipitation and sedimentation processes of hydrometeors are also included in the schemes.…”

“…Some of the earlier studies have suggested that a cumulus scheme is necessary for coarser grid resolution (Nasrollahi et al 2012). However, the inclusion of a cumulus scheme does not help significantly if used in fine scale resolution than that in coarse scale simulation.…”