基于改进U-Net的CMIP5全球气候模式降尺度方法及其在鄱阳湖流域的应用

利用降尺度方法对CMIP5全球气候模式进行空间降尺度并以此研究鄱阳湖流域未来气候时空变化趋势,能够为流域生态环境保护提供数据、技术和理论上的支持.通过简化原始网络结构,在网络首部添加插值层,采用反卷积算法作为上采样算法对传统U-Net网络进行改进,建立基于深度学习的气候模式空间降尺度模型(DLDM).以1965-200...     

The Flexible Global Ocean-Atmosphere-Land system model, Spectral Version 2: FGOALS-s2

The Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 (FGOALS-s2) was used to simulate realistic climates and to study anthropogenic influences on climate change. Specifically, the FGOALS-s2 was integrated with Coupled Model Intercomparison Project Phase 5 (CMIP5) to conduct coordinated experiments that will provide valuable scientific information to climate research communities. The performances of FGOALS-s2 were assessed in simulating major climate phenomena, and documented both the strengths and weaknesses of the model. The results indicate that FGOALS-s2 successfully overcomes climate drift, and realistically models global and regional climate characteristics, including SST, precipitation, and atmospheric circulation. In particular, the model accurately captures annual and semi-annual SST cycles in the equatorial Pacific Ocean, and the main characteristic features of the Asian summer monsoon, which include a low-level southwestern jet and five monsoon rainfall centers. The simulated climate variability was further examined in terms of teleconnections, leading modes of global SST (namely, ENSO), Pacific Decadal Oscillations (PDO), and changes in 19th–20th century climate. The analysis demonstrates that FGOALS-s2 realistically simulates extra-tropical teleconnection patterns of large-scale climate, and irregular ENSO periods. The model gives fairly reasonable reconstructions of spatial patterns of PDO and global monsoon changes in the 20th century. However, because the indirect effects of aerosols are not included in the model, the simulated global temperature change during the period 1850–2005 is greater than the observed warming, by 0.6°C. Some other shortcomings of the model are also noted.     

不同降水方案对"03.7"一次暴雨过程模拟的影响

观测和数值模拟研究已经表明,潜热释放对中国东部夏季梅雨锋系统及其锋面降水的维持和发展发挥着非常重要的作用.然而,目前对于梅雨锋降水模拟中各种降水方案的相互协调和系统评估方面的工作仍不多见,为了增进对梅雨锋暴雨模拟中降水过程的认识,作者针对2003年7月4～5日一次梅雨锋暴雨过程,构造了四组试验,利用MM5模式考察了两种分辨率(36 km、12 km),各种隐/显式方案搭配下,对所生成的雨带、雨量和降水类型的配置进行了仔细的研究,得到了一些有意义的结论,为今后更好地使用模式、利用数值模式来认识中尺度降水过程中的气象问题打下基础.主要结论包括:模拟总降水的水平分布和强度,以及显式降水和隐式降水的划分对积云参数化方案的选择非常敏感.但对特定积云参数化方案而言,降水的模拟对36 km、12 km水平分辨率不敏感(除Betts-Miller方案外);在中尺度网格分辨率10～50 km范围内,不同积云参数化方案对梅雨锋降水分布和降水量模拟的影响比不同显式方案带来的变化大得多.     

Historical Trends in Surface Air Temperature Estimated by Ensemble Empirical Mode Decomposition and Least Squares Linear Fitting

Ensemble empirical mode decomposition(EEMD) and least squares linear fitting(LSLF) are applied to estimate the historical trends of surface air temperature(SAT) from observations and Coupled Model Intercomparison Project Phase 5(CMIP5) simulations during the period 1901–2005. The magnitudes of trends estimated by the two approaches are comparable. The trend calculated by the EEMD approach is larger than that by the LSLF approach in most(23/27) of the models during 1901–2005. During the slow warming period, the EEMD trend is smaller than the LSLF trend. The rootmean-square errors(RMSEs) between the raw and reconstructed times series by the LSLF approach are larger than those by the EEMD trend component and multi-decadal variability components during 1901–2005 in most of the models and observations. During 1901–70(or 1971–2005), the RMSEs between the raw and reconstructed times series by LSLF are larger than those by the EEMD trend component. In this sense, the EEMD trend is a better choice to obtain the climate trends in observations and CMIP5 models, especially for short time periods. This is because the trend estimated by LSLF cannot capture the internal variability and the cooling in some years. The estimated global warming rates(trend) are consistently larger(smaller) than those from observations in 11 of 27 CMIP5 models during 1901–2005 in the slow and rapid warming periods. This implies these 11 models have consistent responses to greenhouse gases for any period.     

WRF和MM5模式对辽宁暴雨模拟的对比分析

用近年开发的新一代中尺度预报模式WRF(Weather Research Forecast)和已被广泛应用的MM5模式分别模拟研究了2002年8月3~4日发生在辽宁的一次区域性暴雨过程。模拟结果显示WRF模式能够比较成功地反映出导致暴雨发生的高低空环流背景和暴雨的分布状况;WRF和MM5模拟结果的对比分析表明:由于WRF的动力框架具有一定的优越性使得模式结果得到改善,在前处理和所选物理过程相同的情况下,WRF模式对能够代表本次暴雨过程中中尺度天气系统的高度场、风场、散度场、水汽通量场以及垂直速度场等物理量的模拟效果要好于MM5。高空形势场的影响使WRF模拟的降水落区和强度更接近实况。     

CMIP5气候模式对中国未来气候变化的预估和应用

气候模式是研究气候系统和气候变化的有力工具,其模拟结果是进行气候预测和气候变化风险评估的重要数据基础。随着全球气候变暖速度加快,地表生态环境、水文动态循环过程、社会经济发展等都受到其影响,进而影响到人类的生产和生活。利用气候模式对未来气候变化特征进行评估和预测,可为人类调整发展策略以适应气候变化提供科学依据。通过汇总CMIP5(Coupled Model Intercomparison Project Phase 5)模式在气候变化方面的相关研究,综述了CMIP5气候模式在农业生产、水文动态监控以及其他领域中的应用,最后指出了CMIP5气候模式在模拟预估未来气候变化上存在的不足,并展望了CMIP5气候模式在未来的应用。     

基于RS和GIS的城市公共绿地功能模糊评价

城市公共绿地具有重要的生态功能和社会功能,良好的评价体系有利于其科学的规划和管理。目前主要采用人均公共绿地和服务半径两个指标对公共绿地质量进行评价,不能较好地评价其生态和社会功能。本文根据公共绿地的功能特点,按照评价体系可操作性和可比性要求,选择单位公园绿化覆盖率、面积大小、公园服务半径内的居民区和单位面积比例、服务半径内道路面积比例作为评价因子。并以山东省泰安市为研究区,利用遥感影像监督分类结合ArcGIS空间分析方法从SPOT5影像中获取评价因子数据,利用多级模糊评判方法对研究区城市公共绿地进行评判。模糊评价结果为泰安市公共绿地的生态功能和社会功能综合得分为77.449分,等级标准为良好。     

2003-06-29暴雨过程条件性对称不稳定分析

利用中尺度模式MM5的部分产品，采用二元法，对2003年6月29-30日淮河流域上游暴雨天气过程中的条件性对称不稳定（CSI）进行了诊断分析，结果表明：此次过程中CSI区出现在对流层中上层，CSI区与对流稳定性大气层结条件下的强降水天气有很好的对应关系；利用MM5输出产品对物理量进行诊断分析，能够较好地解释局地强降水出现的物理机制。     

对流性降水云辐射特性研究

结合MM5模式和三维微波辐射传输模式,对2002年7月22～23日发生在湖北宜昌附近一次中尺度强降水过程中的强降水中心的对流性降水云的微波辐射特性进行了模拟,模拟结果表明：MM5模式可以较好地模拟此次降水过程;云中各微物理量的含量和分布对上行微波辐射亮温有重要影响;就物理方法而言,选用适当的云廓线,是利用微波信息反演降水的关键。     

IRNSS和QZSS在各自主服务区域的L5定位性能评估：独立系统与GPS联合

印度区域导航卫星系统（IRNSS）与日本准天顶系统（QZSS）是近年来宣布正式运行的两个区域卫星导航系统。本文首先评估了IRNSS和QZSS在各自主服务区域的L5信号单点定位性能。然后,为了探究导航星座结构差异对各区域系统联合GPS在城市峡谷环境下定位性能的影响程度,详细对比分析了卫星截止高度角为5°、15°、25°、35°、45°、55°时各区域系统在其主服务区内联合GPS定位的表现。结果表明：① IRNSS在其主服务区内可提供全天连续独立L5定位服务,水平方向定位精度小于2.50m,高程方向定位精度小于4.10m;② QZSS在其主服务区内只能提供全天部分时段的独立L5定位服务,水平方向定位精度小于4.80m,高程方向定位精度小于7.40m;③由于QZSS独特的星座结构,其在主服务区城市峡谷环境中联合GPS定位的性能要优于IRNSS在其相应主服务区联合GPS定位的表现,尤其是在天空视野有限的情况下。本文结果对决策者设计新的区域导航系统具有一定的参考价值。