Improvement of the Mellor–Yamada–Nakanishi–Niino Planetary Boundary-Layer Scheme Based on Observational Data in China

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• 作者：Yi Huang ; Xindong Peng
• 关键词：Closure constant ; Complex underlying surface ; Mellor–Yamada–Nakanishi–Niino model ; Planetary boundary ; layer parametrization ; Turbulent length scale
• 刊名：Boundary-Layer Meteorology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：162
• 期：1
• 页码：171-188
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Atmospheric Sciences; Meteorology; Atmospheric Protection/Air Quality Control/Air Pollution;
• 出版者：Springer Netherlands
• ISSN：1573-1472
• 卷排序：162

文摘

The Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer (PBL) scheme is a second-order turbulence closure model that is an improved version of the Mellor–Yamada scheme based on large-eddy simulation data. It simulates PBL structure and evolution well, particularly over the ocean surface. However, when used with various underlying surfaces in China, the scheme overestimates the turbulent momentum flux and the sensible heat flux. Based on observations of surface fluxes in China, we attempt to improve the MYNN model by modifying the parameters and representation of the turbulence scale. Closure constants and empirical expressions in the diagnostic equation are chosen first, and an additional component of the turbulent heat flux is considered in the potential temperature prognostic equation to improve the surface heat-flux modelling. The modified MYNN scheme is incorporated into a three-dimensional mesoscale model and is evaluated using various underlying surface observations. Amelioration of the surface turbulent fluxes is confirmed at five observational sites in China over different land-use types.