3篇
您的检索式：作者名="KOU Xingxia"
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| 1 | Assessment of the Biospheric Contribution to Surface Atmospheric CO_2 Concentrations over East Asia with a Regional Chemical Transport Model显示文摘A regional chemical transport model, RAMS-CMAQ, was employed to assess the impacts of biosphere–atmosphere CO2 exchange on seasonal variations in atmospheric CO2 concentrations over East Asia. Simulated CO2 concentrations were compared with observations at 12 surface stations and the comparison showed they were generally in good agreement. Both observations and simulations suggested that surface CO2 over East Asia features a summertime trough due to biospheric absorption, while in some urban areas surface CO2 has a distinct summer peak, which could be attributed to the strong impact from anthropogenic emissions. Analysis of the model results indicated that biospheric fluxes and fossil-fuel emissions are comparably important in shaping spatial distributions of CO2 near the surface over East Asia. Biospheric flux plays an important role in the prevailing spatial pattern of CO2 enhancement and reduction on the synoptic scale due to the strong seasonality of biospheric CO2 flux. The elevation of CO2 levels by the biosphere during winter was found to be larger than 5ppm in North China and Southeast China, and during summertime a significant depletion( 7 ppm) occurred in most areas,except for the Indo-China Peninsula where positive bioflux values were found. | KOU Xingxia ZHANG Meigen PENG Zhen WANG Yinghong | 2015 | Advances in Atmospheric Sciences2015，32，3： | 4 |
| 2 | Accounting for CO2 Variability over East Asia with a Regional Joint Inversion System and Its Preliminary Evaluation显示文摘A regional surface carbon dioxide(CO_2) flux inversion system, the Tan-Tracker-Region, was developed by incorporating an assimilation scheme into the Community Multiscale Air Quality(CMAQ) regional chemical transport model to resolve fine-scale CO_2 variability over East Asia. The proper orthogonal decomposition-based ensemble four-dimensional variational data assimilation approach(POD-4 DVar) is the core algorithm for the joint assimilation framework, and simultaneous assimilations of CO_2 concentrations and surface CO_2 fluxes are applied to help reduce the uncertainty in initial CO_2 concentrations. A persistence dynamical model was developed to describe the evolution of the surface CO_2 fluxes and help avoid the 'signal-to-noise' problem; thus, CO_2 fluxes could be estimated as a whole at the model grid scale, with better use of observation information. The performance of the regional inversion system was evaluated through a group of single-observation-based observing system simulation experiments(OSSEs). The results of the experiments suggest that a reliable performance of Tan-Tracker-Region is dependent on certain assimilation parameter choices, for example, an optimized window length of approximately 3 h, an ensemble size of approximately 100, and a covariance localization radius of approximately 320 km. This is probably due to the strong diurnal variation and spatial heterogeneity in the fine-scale CMAQ simulation, which could affect the performance of the regional inversion system. In addition, because all observations can be artificially obtained in OSSEs, the performance of Tan-Tracker-Region was further evaluated through different densities of the artificial observation network in different CO_2 flux situations. The results indicate that more observation sites would be useful to systematically improve the estimation of CO_2 concentration and flux in large areas over the model domain. The work presented here forms a foundation for future research in which a thorough estimation of CO_2 flux variability over East Asia could be performed with the regional inversion system. | xingxia kou xiangjun tian meigen zhang zhen peng xiaoling zhang | 2017 | Journal of Meteorological Research2017，31，5： | 2 |
| 3 | Simulation and Projection of Near-Surface Wind Speeds in China by BCC-CSM Models显示文摘We evaluated the ability of the Beijing Climate Center models on different horizontal resolutions(BCC-CSM1.1 on approximately 280-km resolution and BCC-CSM1.1 m on approximately 110-km resolution) in simulating the nearsurface wind speeds(NWS) in China during 1961–2005. The spatial distribution of the annual mean NWS over China is better captured by BCC-CSM1.1 m than by BCC-CSM1.1 due to the finer resolution. The weakened NWS over China during 1961–2005 cannot be reproduced by BCC-CSM1.1, whereas BCC-CSM1.1 m is able to simulate the decreasing trend of the autumn NWS in North China, although the magnitude is about 1/3 of the observed value.This is attributed to the better performance of this finer-resolution model in reproducing the increase in sea level pressure over Mongolia and North China over the past 45 years. The results suggest that increasing the horizontal resolution of the BCC-CSM model has improved its ability in reproducing the spatial distribution and long-term changes of NWS over China. Future projections by BCC-CSM1.1 m under different Representative Concentration Pathway(RCP) scenarios demonstrate that the autumn NWS in North China will decrease during the 21 st century under both the middle(RCP4.5) and high(RCP8.5) emission scenarios, with a higher decreasing rate under RCP8.5. | Yajun XIONG Xiaoge XIN Xingxia KOU | 2019 | Journal of Meteorological Research2019，33，1： | 1 |
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