高寒草原地区边界层参数化方案的适用性评估

Applicability Research of Planetary Boundary Layer Parameterization Scheme in WRF Model over the Alpine Grassland Area

为了验证中尺度数值模式WRF中不同的边界层参数化方案对青藏高原地区高寒草原均匀下垫面的适用性,选取4种不同的边界层参数化方案(YSU、MYNN2.5、ACM2和BouLac),分别在青藏高原东部玛曲地区进行了高分辨率的数值模拟,借助中国科学院寒区旱区环境与工程研究所若尔盖高原湿地生态系统研究站观测资料,对典型晴天条件下近地层温度、辐射收支、地表能量以及边界层结构特征进行了相互比较分析,评估了不同边界层参数化方案的模拟差异。结果表明,对于近地层温度,白天不同方案的模拟值与观测值差异不明显,夜间MYNN2.5方案更偏离观测值,而其余方案的模拟差异不大;相对短波辐射,长波辐射过程更易受边界层参数化方案的影响;对于地表热通量,非局地闭合方案的模拟值相对湍流动能TKE闭合方案更接近观测值;对于净辐射通量、感热通量和潜热通量,MYNN2.5方案的模拟要优于其他3种方案;不同边界层参数化方案均模拟出了白天超绝热层以及夜间逆温、逆湿现象,但不同方案对边界层结构的模拟仍然存在一些差异。

To verify the applicability of the WRF model to the underlying surface area, using the ob- servation data at the Zoige field over the alpine grassland area, the high-resolution simulations on some me- teorological variables in several clear days are inter-compared and evaluated quantitatively using the WRF model with four planetary boundary layer（PBL） parameterization schemes. The results show that： For 2 m temperature, all schemes give no significant differences with the observed values in daytime, while MYNN2.5 scheme shows farther away from the observed values and the differences are not obvious among other schemes at nighttime. Comparing with the shortwave radiation, the simulations of longwave radia- tion are more susceptible to PBL schemes. All simulations of ground heat flux with non-local schemes show much less bias thanthat with the TKE schemes. The simulations of net radiation flux, sensible heat flux and latent heat flux with MYNN2.5 scheme have the best relationship with the observed values than that with other schemes. Moreover, the super-adiabatic phenomenon, temperature inversion and humidity inversion are well simulated by all schemes, even though there are some differences between different PBL schemes.