Comparison of planetary boundary layer schemes in WRF model for forecasting ramp phenomena in wind power generation

  • Yasuhiko Azegami, 2016: Comparison of planetary boundary layer schemes in WRF model for forecasting ramp phenomena in wind power generation .

Abstract


This study evaluatd on atmospheric and terrain factors causing ramp phenomena in Rumoi,Nemuro, Esashi and Obihiro in Hokkaido,by using surface observation data. Additionally, characteristics of the ramp phenomena were individually investigated for each area from 2011 to 2013. The investigation revealed that the most appearing factor causing the ramp phenomena is the approach or passage of low pressure system, second is the major pressure pattern in winter, third is the existence of high pressure systems, forth is the passage of front systems. Generally, ramp phenomena are mainly caused by synoptic scale phenomena. While, the growth of planetary boundary layer (PBL) could be also a reason for ramp phenomena. Many ramp phenomena occur in the morning. Because after sunrise, the development of PBL due to surface heating brings the downward momentum transportation from upper to lower layers. This study also examined the influence of PBL schemes (Mellor-Yamada-Janjic: MYJ, Yonsei-University: YSU, Mellor-Yamada-Nakanishi-Niino level3: MYNN3) introduced in WRF model on ramp phenomena forecasts. In a 2D-idealized experiment simulated heights of PBL depended on PBL schemes. The YSU scheme simulated higher PBL than other schemes, and the MYJ scheme simulated the lowest PBL.A real case experiment which focused on ramp phenomena caused by high pressure systems or major winter pressure pattern was performed, because the development of PBL is more clearly found than that for the other factors. However, the dependent on PBL schemes was not found in the simulation result. An additional experiment with uses different initial and boundary conditions showed that the influence of PBL schemes is smaller than that of initial and boundary conditions. Therefore, the influence of PBL schemes is has little impact to the result of forecasting ramp phenomena. Consequently, the choice of initial and boundary conditions is more important than that of PBL schemes. The prediction accuracy of ramp phenomena was also examined for PBL schemes. The MYJ scheme had the highest capture rate, and the YSU scheme had the lowest capture rate. The MYNN3 scheme had the highest hit rate, and the MYJ scheme had the lowest hit rate.

Keywords : Wind power generation, Ramp phenomena, Planetary boundary scheme, Hokkaido