The aerodynamic roughness length ( Z 0 ) plays an important role in the land–air exchange. At present, the atmospheric numerical models cannot accurately describe the Z 0 in different underlying surfaces, which affects the simulation performance and the description of the momentum and heat exchange and atmospheric environment. In this study, the regional air quality model WRF/Chem with updated Z 0 of the various underlying surface categories is used to study the impacts of Z 0 on the boundary layer meteorological conditions and atmospheric environment over the Pearl River Delta (PRD) region. Two numerical experiments are conducted, including default Z 0 (Base experiment) and updated Z 0 (Case experiment). By comparing the simulations with the observations from 9 meteorological stations and 30 national air quality monitoring stations, the updated Z 0 improves the model simulation performance of 10 m wind speed in PRD. The impacts of updated Z 0 on 2 m temperature and relative humidity are relatively small, while the influences of updated Z 0 on surface skin temperature (TSK), ground heat flux (GRDFLX), sensible heat flux (HFX), friction velocity ( U *), 10 m wind speed (WS) and planetary boundary layer height (PBLH) are evident. The impacts of updated Z 0 in the urban are greater than that in the evergreen broadleaf forest. In the urban, the updated Z 0 reduces TSK, lowers GRDFLX, increases HFX during the daytime, and increases U *, causing the reduction of WS, while the vertical velocity also increases, which is conducive to the elevation of PBLH. With the updated Z 0 , the surface carbon monoxide (CO) concentrations generally increase, especially in the central urban areas, due to the impact of wind speed, turbulent motion and planetary boundary layer height. The updated Z 0 has a little impact on CO concentration profile during the daytime, which is affected by horizontal wind speed and turbulent motion; while at night, the updated Z 0 produces an increase of CO concentration below 300 m, which is affected by the horizontal wind speed.

中文翻译：

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评估更新的空气动力学粗糙度长度在 WRF/Chem 模型中对珠江三角洲的影响

空气动力学粗糙度长度（Z 0 ）在陆气交换中起着重要作用。目前，大气数值模型不能准确描述不同下垫面的Z 0 ，影响了模拟性能和动量热交换和大气环境的描述。本研究采用区域空气质量模型WRF/Chem更新了各种下垫面类别的Z 0 ，研究Z 0 对珠江三角洲（PRD）地区边界层气象条件和大气环境的影响。进行了两个数值实验，包括默认的 Z 0（基础实验）和更新的 Z 0（案例实验）。通过将模拟结果与 9 个气象站和 30 个国家空气质量监测站的观测结果进行比较，更新后的 Z 0 提高了珠三角地区 10 m 风速的模型仿真性能。Z 0 更新对2 m温度和相对湿度的影响较小，而Z 0 更新对地表表皮温度（TSK）、地热通量（GRDFLX）、显热通量（HFX）、摩擦速度（ U *)、10 m 风速 (WS) 和行星边界层高度 (PBLH) 很明显。Z 0 更新对城市的影响大于常绿阔叶林。在市区，更新后的 Z 0 降低了 TSK，降低了 GRDFLX，白天增加了 HFX，增加了 U*，导致 WS 降低，同时垂直速度也增加，有利于 PBLH 的抬高。随着 Z 0 的更新，地表一氧化碳 (CO) 浓度普遍增加，尤其是在中心城区，由于风速、湍流运动和行星边界层高度的影响。更新后的 Z 0 对白天的 CO 浓度剖面影响不大，受水平风速和湍流运动的影响；而在夜间，更新后的 Z 0 会导致 300 m 以下的 CO 浓度增加，这受水平风速的影响。