Estimation of vegetation underlying surface Z0 and assessment on the impacts of its improvement
TIAN Chun-yan1,2, CUI Yin-ping1, SHEN Chong3, CHEN Xiu-zhi1, SHEN Ao1, FAN Qi1
1. Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Southern Laboratory of Ocean Science and Engineering (Zhuhai), School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082, China; 2. Meteorological Center of Middle South Regional Air Traffic Management Bureau of CAAC, Guangzhou 510000, China; 3. Guangzhou Climate and Agrometeorology Center, Guangzhou 511430, China
Abstract：The morphology-remote sensing inversion with satellite remote sensing and multi-observation data were utilized to estimate the aerodynamic roughness length (Z0) of main vegetation underlying surfaces in China. This new Z0 dataset was then used to replace the default values in the WRF-Chem model. Combined with the national meteorological and pollutant observation data, the impacts of Z0 improvement on the meteorological field and chemical field simulations were evaluated. The results show that the high value of Z0 is mainly located over the forest underlying surface (higher than 1m); the Z0 values over the farmland and grassland underlying surfaces are generally lower (lower than 0.5m). The Z0 values over other underlying surfaces fell in between 0.5m and 1m; and the modification of Z0 has a better improvement in the simulations of 10m wind speed (WS10) and surface temperature (TSK) even though its effects on 2m temperature (T2) and relative humidity (RH) are not obvious. We also observed that an increase in Z0 mainly has a warming effect on TSK and a weakening effect on WS10 for different types of underlying surfaces. In terms of the improvement ratio (the difference between the simulated value after the improvement of each element and the simulated value before the improvement divided by the simulated value before the improvement, the same below), the improved Z0 demonstrates a greater impact on WS10 than on TSK. For the pollutant concentrations, the modification of Z0 has larger effects on the simulations for PM2.5 and PM10 than for other pollutants (SO2, NO2, O3). Furthermore, the impact of the improved Z0 was larger on meteorological elements than on pollutant concentrations. In general, the improvement of Z0 has the largest impact on the 10m wind speed; because the improved Z0 is generally higher than the model-default Z0 value. As Z0 is a variable for characterizing the surface roughness, the obstruction to the air flow increases with an increase in surface roughness and thus results in a reduction in the near surface wind speed.
田春艳, 崔寅平, 申冲, 陈修治, 沈傲, 樊琦. 植被下垫面Z0的估算及其改进影响评估[J]. 中国环境科学, 2022, 42(9): 3969-3982.
TIAN Chun-yan, CUI Yin-ping, SHEN Chong, CHEN Xiu-zhi, SHEN Ao, FAN Qi. Estimation of vegetation underlying surface Z0 and assessment on the impacts of its improvement. CHINA ENVIRONMENTAL SCIENCECE, 2022, 42(9): 3969-3982.
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