青藏高原的气候植被模型研究进展

气候植被研究是全球变化研究的重要内容, 而模型研究是气候植被研究的重要手段。青藏 高原以其特殊的自然环境特点, 形成了气候与植被独特的适应机制, 为许多通用气候植被模型所 不能反映, 加之所受到人类活动的干扰相对较少, 决定其为植被气候研究的重要实验场地。本文 回顾了气候植被模型发展的相关历程, 评述了每类模型的特点及其不足。从植被格局研究和植被 生产力研究两个方面, 对青藏高原的气候植被研究进行了总结和分析, 认为模型研究是气候植被 研究的重要手段, 而青藏高原的研究在这方面还比较落后, 同时对青藏高原气候植被模型研究中 存在的一些问题, 如数据精度、模型的适宜性和结果验证等进行了讨论。认为今后青藏高原气候 植被模型研究的重点应是进一步明晰气候植被的关键过程, 立足高原环境特点开发有高原特色 的气候植被模型。     

气候变化背景下森林动态模拟研究综述

在全球气候变化背景下,森林的地理分布与生态过程研究受到越来越多的关注.森林对气候变化的响应是一个复杂的过程,在已有模拟方法中,林窗模型和全球植被动态模型由于考虑了气候作用下植被的演替与更新等机理,能较为合理地模拟气候变化背景下森林的瞬态响应,是目前气候变化研究的热点之一.全球植被动态模型以植物功能类型(PFTs)表示区域森林植被组成,通过模拟PFTs比例的变化来反映森林地理分布格局的动态变化.通过回顾上述两类模型的发展历程,梳理了模型在模拟研究森林地理分布及生态过程中,对过去和未来气候变化的潜在响应方面的应用,并针对模型中存在的不足,提出今后应在动态模型多尺度研究、加强模型对非气候因子的描述、模型间比较、多源遥感数据与模型同化等方面开展重点研究.     

A two-parameter exponential recession model for simulating cropland soil moisture dynamics

To simulate the soil moisture variation in cropland, a two-parameter exponential recession model was derived to depict the recession process of soil moisture in the root zone. The model is based on the assumption that the recession rate of soil water is propor- tional to the potential evapotranspiration rate and the difference of soil water content and steady soil water content. Two parameters in this model are soil texture-dependent recession constant and steady soil water content. The model was calibrated and validated with measured soil water data at two experiment sites in North China with different soil textures and cropping systems. Coefficients of de- termination between measured and model simulated soil water content were all greater than 0.7, indicating that both models gave satis- factory simulation results. Results showed that values of two parameters mentioned above are both larger for finer soil than those for coarser soil. At the same potential evapotranspiration rate and soil water content, the recession rate of finer soil is usually lower than that of coarser soil. The proposed model can be used in irrigation management to predict approximate date for irrigation, as well as be em- bedded into watershed hydrological models to estimate the antecedent precipitation index.     

Model simulations of mesoscale eddies and deep convection in the Labrador Sea

Deep convection in the Labrador Sea is confined within a small region in the southwest part of the basin.The strength of deep convection in this region is related to the local atmospheric and ocean characteristics,which favor processes of deep convection preconditioning and intense air-sea exchange during the winter season.In this study,we explored the effect of eddy-induced flux transport on the stratification of the Labrador Sea and the properties of deep convection.Simulations from an eddy-resolving ocean model are presented for the Labrador Sea.The general circulation was well simulated by the model,including the seasonal cycle of the deep Labrador Current.The simulated distribution of the surface eddy kinetic energy was also close to that derived from Topex-Poseidon satellite altimeter data,but with smaller magnitude.The energy transfer diagnostics indicated that Irminger rings are generated by both baroclinic and barotropic processes; however,when they propagate into the interior basin,the barotropic process also disperses them by converting the eddy energy to the mean flow.In contrast to eddy-permitting simulations,deep convection in the Labrador Sea was better represented in the eddyresolving model regarding their lateral position.Further analysis indicated that the improvement might be due to the lateral eddy flux associated with the resolved Irminger rings in the eddy-resolving model,which contributes to a realistic position of the isopycnal dome in the Labrador Sea and correspondingly a realistic site of deep convection.     

Temperature biases in modeled polar climate and adoption of physical parameterization schemes

An annual cycle of atmospheric variations for 1989 in the Arctic has been simulated with the Weather Research and Forecasting （WRF） model. A severe cold bias was found around a cold center in surface air temperature over the Arctic Ocean, compared with results from ERA-Interim reanalysis. Four successive numerical experiments have been carried out to find out the reasons for this. The results show that the sea ice albedo scheme has the biggest influence in summer, and the effect of the cloud microphysics scheme is significant in both summer and winter. The effect of phase transition between ice and water has the biggest influence over the region near the sea ice edge in summer, and contributes little to improvement of the severe cold bias. The origi- nal crude albedo parameterization in the surface process scheme is the main reason for the large simulated cold bias of the cold center in summer. With a different land surface scheme than in the control run, cold biases of simulated surface air temperature over the Arctic Ocean are greatly reduced, by as much as 10 K, implying that the land surface scheme is critical for polar climate simulation.     

Recent changes of Northern Indian Ocean summer rainfall based on CMIP5 multi-model

This study evaluates the simulation of summer rainfall changes in the Northern Indian Ocean (NIO) based on the fifth phase of Coupled Model Intercomparison Project (CMIP5). The historical runs of 20 CMIP5 coupled General Circulation Models (GCMs) are analyzed. The Multi-Model ensemble (MME) of the CMIP5 models well reproduces the general feature of NIO summer rainfall. For a short period 1979–2005, 14 out of 20 models show an increased trend in the mean rainfall and a similar spatial distribution to the Global Precipitation Climatology Project (GPCP) observations in MME. The increasing of the convergence in the equatorial IO results in the increase of rainfall significantly. The equatorial rainfall trend patterns seem modulated by the SST warming in the tropical Indian Ocean, which confirm the mechanism of ‘warmer-get-wetter’ theory. For a long period 1950–2005, the trend of monsoon rainfall over India shows a decrease over the most parts of the India except an increase over the south corn er of the Indian Peninsula, due to a weakened summer monsoon circulation. The pattern is well simulated in half of the CMIP5 models. The rainfall over the north India is different for a short period, in which rainfall increases in 1979–2005, implying possible decadal variation in the NIO summer climate.     

国际LUCC模型研究进展及趋势

LUCC模型有助于深刻理解土地利用系统动态.经过10多年的发展,LUCC模型在理论和实践方面有了很大发展.开发新一代LUCC模型成为了GLP的一项重要任务.在大量阅读分析国际上LUCC模型应用研究的基础上.基于土地利用变化与骄动力之间相互作用表征方法的差异,从认识论的角度出发,本文将LUCC模型概括为经验一统计模型、概念机理模型和综合模型,并分别对各类模型的概念、技术方法、应用以及存在的缺陷等进行了分析.发现各种模型均能够解决特定的LUCC问题,同时也存在着缺陷和局限性.目前,LUCC建模中仍存在着时空尺度和数据方面的问题,未来LUCC模型发展趋势主要表现在解决LUCC中多尺度问题,评价和解决空间领域效应和时间动态方而的问题,土地系统可持续性综合分析与建模等方面.     

Impact of global SST on decadal shift of East Asian summer climate

East Asia experienced a significant interdecadal climate shift around the late 1970s, with more floods in the valley of the Yangtze River of central-eastern China and more severe drought in North China since then. Whether global SST variations have played a role in this shift is unclear. In the present study, this issue is investigated by ensemble experiments of an atmospheric general circulation model (AGCM), the GFDL AM2, since one validation reveals that the model simulates the observed East Asian Summer Monsoon (EASM) well. The results suggest that decadal global SST variations may have played a substantial role in this climate shift. Further examination of the associated atmospheric circulation shows that these results are physically reasonable.     

大数据城市通勤交通模型的构建与模拟应用

近年来大数据在交通分析中被广泛关注,但目前多以可视化展示和现象空间分析描述为主,缺乏基于大数据的交通数量模型和模拟预测研究,成为大数据技术在交通规划中应用的主要技术障碍。本文基于交通与土地利用之间的交互作用关系,构建区位空间依赖因子（(Location-space Dependence Indicator, LSDI）,对传统重力模型进行改进,提出大数据城市通勤分布模型。以北京市为例,采用某运营商2017年9月的手机信令大数据,进行模型的应用和校验。模拟结果显示,在出行产生预测中,通勤人口与常住人口表现出良好的线性关系;在出行分布预测中,基于区位空间依赖因子的修正重力模型综合表现最优,在通勤OD分布中实现了低估现象的优化,在OD数量发生率中拟合优度达到0.85。本研究为大数据城市交通预测模型研发提供了新的技术方法,对于推动大数据在交通规划中的应用具有一定价值。     

未来中国东部地区夏日将更炎热

<正>由于人类活动对气候的影响,现在中国东部地区夏天发生酷热天气的概率要比1950年多出60倍,在线发表于《自然—气候变化》上的一项研究得出该结论。如果未来温室气体的排放被控制在中等水平,那么这种酷热事件发生的趋势仍可能持续,接下来到2024年的这10年里,将有一半的夏天的气温会与2013年夏天日均35℃的气温持平。Xuebin Zhang等人分析了20世纪50年代到2013年间的中国东部地区气温记录来研究