WRF Simulation of Typhoon-induced Heavy Precipitation Over the Philippines: Applicability and Performance of the Multi-scale Kain-Fritsch Cumulus Scheme
Cumulus parameterization schemes, which handle convection processes such as those involving moisture and precipitation, have been indispensable in simulations using numerical weather prediction models such as the Weather Research and Forecasting (WRF) model. The Kain-Fritsch (KF) is one of the most-used schemes in WRF. An improved and scale-aware version of this scheme, called Multi-scale KF (MSKF), was produced in 2015. Limited studies have proven that using MSKF brings improvement to the simulated precipitation values, which are usually overestimated by KF. However, the applicability and performance of MSKF over the Philippines in simulating precipitation are yet to be verified. Herein, we examined these by simulating Typhoon Koppu and comparing the hourly and daily results with those of two other cumulus schemes – KF and Grell-Freitas (GF). Six simulations were conducted – three use cumulus schemes in high resolution (5 km, innermost domain), and three do not. Based on the results, the MSKF is applicable for use in simulating precipitations, including typhoon-induced heavy precipitations, over the Philippines. It is best used when a typhoon is at its strongest but underperforms when the typhoon is weak and nearing dissipation. However, GF performs best among the three schemes. Additionally, the results show that using cumulus schemes in high resolution (5 km, using nests) does not always improve, sometimes even deteriorate, the performance of simulations in producing accurate precipitation values. Further investigations should be conducted regarding the performance of MSKF in simulating heavy precipitations over the Philippines and neighboring areas.
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