春季黄海海雾 WRF 参数化方案敏感性研究

摘要

利用2005-2011年10次春季黄海海雾个例开展 WRF 模式参数化方案敏感性研究。结果表明：边界层方案对 WRF 模式雾区模拟结果起决定作用，而微物理方案影响较小，它主要影响海雾浓度和高度。边界层与微物理方案的最佳组合为 YSU 与 Lin 方案，最差为 Mellor-Yamada 与 WSM5方案；Mellor-Yamada 和 QNSE 方案模拟的近海面湍流过强，导致边界层过高，不利于海雾的发展与维持；而 MYNN 与 YSU 方案刻画的湍流强度与边界层高度合适，有利于海雾发展与维持。MYNN 方案虽与 YSU 方案相当，但在大多数海雾个例中，后者明显优于前者，而在有些个例中却刚好相反。因此对于某一具体海雾个例而言，所用边界层方案仍需在它们之中选择最优者。这些信息可为黄海海雾 WRF 模式边界层与微物理方案的选择与改进提供参考。%Sea fog is a water vapor condensation phenomenon,which happens in marine atmospheric boundary layer (MABL).Low atmospheric visibility caused by sea fog brings huge threat to maritime transporta-tion,fishery and oil-drilling operations.Therefore,it is becoming increasingly important and being paid more and more attention.In recent years,meso-scale atmospheric numerical modeling has become a domi-nant way for the mechanism study and numerical modeling of sea fog. Previous studies on sea fog indicate that sea fog modeling is very sensitive to initial conditions,espe-cially realistic representation of temperature and humidity profile in MABL.Besides initial conditions,tur-bulence process and cloud generating process are the other important aspects for sea fog modeling.In a me-so-scale atmospheric numerical model,the turbulence process is described by planetary boundary layer (PBL)scheme,and the cloud generating process is determined by microphysics (MP)scheme.Due to the uncertainties of the modeling result and the complexities of turbulence and cloud microphysics processes, many options of PBL and MP schemes are available for choice focusing on different modeling purposes. Based on the Weather Research and Forecasting (WRF)model and cycling three-dimensional varia-tional method,sensitivity study of WRF PBL and MP schemes for the Yellow Sea fog is conducted,focu-sing on 10 typical widely-spread sea fog cases.The result indicates that simulated sea fog area mostly de-pends on PBL scheme but little on MP scheme;density and depth of simulated sea fog are affected by MP scheme with cloud droplet number being predicted and how it is prescribed.The best combination of PBL and MP schemes is YSU and Lin,while the worst is Mellor-Yamada and WSM5.The Mellor-Yamada and QNSE scheme brings about much stronger turbulence simulation,resulting in much higher boundary lay-er,and therefore it’s not favorable to the development and maintenance of sea fog,while turbulence inten-sity and boundary layer height produced by MYNN and YSU schemes benefit sea fog developing.MYNN scheme can match YSU scheme in general,however,the latter performs better in most cases while the for-mer is better in certain ones.In depth investigation is needed to tell whether MYNN or YSU PBL scheme is better for a given sea fog case.These information can provide hints to choose and improve PBL and MP schemes of WRF for the Yellow Sea fog numerical prediction system in the near future.