Zou Liwei

Development and evaluation of a regional ocean-atmosphere cou-pled model with focus on the western North Pacific summer mon-soon simulation: Impacts of different atmospheric components

A regional ocean atmosphere coupled model (ROAM) is developed through coupler OASIS3, and is composed of regional climate model RegCM3 and CREM (Climate version of Regional Eta Model) as its atmospheric component and of a revised Princeton ocean model (POM2000) as its oceanic component. The performance of the ROAM over the western North Pacific summer monsoon region is assessed by the case simulation of warm season in 1998. Impacts of different atmospheric model components on the performance of ROAM are investigated. Compared with stand-alone simulation, CREM (RegCM3) produces more (or less) rainfall over ocean area with inclusion of the air-sea coupling. Different biases of rainfall are caused by the different biases of SST derived from the coupled simulation. Warm (or cold) SST bias simulated by CREM_CPL (RegCM3_CPL) increases (or decreases) the evaporation at sea surface, then increases (or decreases) the rainfall over ocean. The analyses suggest that the biases of vertical profile of temperature and specific humidity in stand-alone simulations may be responsible for the SST biases in regional coupled simulations. Compared with reanalysis data, the warmer (or colder) and moister (or dryer) lower troposphere simulated in CREM (RegCM3) produces less (or more) sea surface latent heat flux. Meanwhile, the more unstable (or stable) lower troposphere produces less (or more) cloudiness at low-level, which increases (or decreases) the solar radiation reaching on the sea surface. CREM (RegCM3) forced by observed SST overestimates (or underestimates) the sea surface net heat flux, implying a potential warm (or cold) heat source. After coupling with POM2000, the warm (or cold) heat source would further increase (or decrease) the SST. The biases of vertical profile of temperature and specific humidity may be ascribed to the different representation of cumulus convection in atmospheric models.

Indian Ocean SST Biases in a Flexible Regional Ocean Atmosphere Land System (FROALS) Model

Abstract The authors examine the Indian Ocean sea surface temperature (SST) biases simulated by a Flexible Regional Ocean Atmosphere Land System (FROALS) model. The regional coupled model exhibits pronounced cold SST biases in a large portion of the Indian Ocean warm pool. Negative biases in the net surface heat fluxes are evident in the model, leading to the cold biases of the SST. Further analysis indicates that the negative biases in the net surface heat fluxes are mainly contributed by the biases of sensible heat and latent heat flux. Near-surface meteorological variables that could contribute to the SST biases are also examined. It is found that the biases of sensible heat and latent heat flux are caused by the colder and dryer near-surface air in the model.

东亚夏季风变化机理的模拟和未来变化的预估:成绩和问题、机遇和挑战

东亚夏季风对于我国东部气候具有重要影响，呈现出多种时间尺度的变化特征。在理解东亚夏季风过去和当前的变化机理、预测和预估其未来变化等方面，气候系统模式发挥着不可替代的作用。但是当前的气候模式在东亚夏季风的模拟上尚存在诸多不足，这使得其模拟结果存在不确定性，既制约了我们对过去和当前季风变化机理的准确理解，又降低了未来预测预估结果的可信度。关于造成季风模拟偏差的原因，既涉及模式本身的性能问题，又与模拟系统的构建、强迫资料的误差、乃至我们当前对季风变化规律自身的认知水平有关。本文以时间尺度为序，从气候态、日变化、年际变率、年代际变率、长期气候变化和未来预估等季风学界关注的热点问题角度，本着总结成绩、归纳问题、寻找机遇、面对挑战的目的，从七个方面系统总结了当前气候模式的水平，归纳了其主要偏差特征，讨论了影响模式性能的可能因素。内容涉及模式分辨率和地形效应、对流和云辐射效应的作用、与季风相关的热带海气相互作用关键过程、内部变率（太平洋年代际振荡）、自然变率（太阳辐照度变化和火山气溶胶强迫）和人为辐射强迫（人为温室气体和气溶胶排放）对季风变化的不同影响、热力和动力过程及气候敏感度对季风环流（副高）和降水预估不确定性的影响等。最后从优化参数、实现场地观测和过程模拟的协同、发展高分辨和对流解析模式等角度，讨论了提升东亚夏季风模拟能力的技术途径。

Synthesis and biological evaluation of hydroxylcoumarin derivatives as antioxidant agents

In this study, esculetin(1) was chosen as a lead compound and some structural modifications were designed to explore the antioxidant activities of esculetin derivatives. Meanwhile, a convenient method for selective methylation of catechol coumarins with different bases was developed. Furthermore, a few 5,7-dihydroxylcoumarins were synthesized and 7-hydroxylcoumarins were employed in order to explore the potential structure-antioxidant activity relationships. The antioxidant activities of these compounds were evaluated and compared with standard antioxidant Trolox by the 2,2′-diphenyl-1-picrylhydrazyl(DPPH) assay, 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonate) cation(ABTS+) assay and ferric reducing antioxidant power(FRAP) assay. The results show that the catechol group is the key pharmacophore. Meanwhile, introducing electronegative groups at the C4 position of esculetin(1) may enhance the antioxidative capacity, while introducing a group containing nitrogen as a hydrogen bond acceptor at the C8 position may slightly reduce the antioxidative capacity. Among them, the most powerful antioxidants are com-pounds 5 and 7, which exhibit higher antioxidant activity than esculetin(1) in all assays.