Petrology,mineralogy, and oxygen isotope compositions of aluminum‐rich chondrules from CV3 chondrites

Bulk major element composition, petrography, mineralogy, and oxygen isotope compositions of twenty Al‐rich chondrules (ARCs) from five CV3 chondrites (Northwest Africa [NWA] 989, NWA 2086, NWA 2140, NWA 2697, NWA 3118) and the Ningqiang carbonaceous chondrite were studied and compared with those of ferromagnesian chondrules and refractory inclusions. Most ARCs are marginally Al‐richer than ferromagnesian chondrules with bulk Al₂O₃ of 10–15 wt%. ARCs are texturally similar to ferromagnesian chondrules, composed primarily of olivine, pyroxene, plagioclase, spinel, Al‐rich glass, and metallic phases. Minerals in ARCs have intermediate compositions. Low‐Ca pyroxene (Fs_0.6–8.8Wo_0.7–9.3) has much higher Al₂O₃ and TiO₂ contents (up to 12.5 and 2.3 wt%, respectively) than that in ferromagnesian chondrules. High‐Ca pyroxene (Fs_0.3–2.0Wo_33–54) contains less Al₂O₃ and TiO₂ than that in Ca,Al‐rich inclusions (CAIs). Plagioclase (An_77–99Ab_1–23) is much more sodic than that in CAIs. Spinel is enriched in moderately volatile element Cr (up to 6.7 wt%) compared to that in CAIs. Al‐rich enstatite coexists with anorthite and spinel in a glass‐free chondrule, implying that the formation of Al‐enstatite was not due to kinetic reasons but is likely due to the high Al₂O₃/CaO ratio (7.4) of the bulk chondrule. Three ARCs contain relict CAIs. Oxygen isotope compositions of ARCs are also intermediate between those of ferromagnesian chondrules and CAIs. They vary from ?39.4‰ to 13.9‰ in δ¹⁸O and yield a best fit line (slope = 0.88) close to the carbonaceous chondrite anhydrous mineral (CCAM) line. Chondrules with 5–10 wt% bulk Al₂O₃ have a slightly more narrow range in δ¹⁸O (?32.5 to 5.9‰) along the CCAM line. Except for the ARCs with relict phases, however, most ARCs have oxygen isotope compositions (>?20‰ in δ¹⁸O) similar to those of typical ferromagnesian chondrules. ARCs are genetically related to both ferromagnesian chondrules and CAIs, but the relationship between ARCs and ferromagnesian chondrules is closer. Most ARCs were formed during flash heating and rapid cooling processes like normal chondrules, only from chemically evolved precursors. ARCs extremely enriched in Al and those with relict phases could have had a hybrid origin (Krot et al. 2002) which incorporated refractory inclusions as part of the precursors in addition to ferromagnesian materials. The occurrence of melilite in ARCs indicates that melilite‐rich CAIs might be present in the precursor materials of ARCs. The absence of melilite in most ARCs is possibly due to high‐temperature interactions between a chondrule melt and the solar nebula.     

基于模拟脚本的气象自动绘图系统

气象自动绘图系统（MEPAS）是一款紧贴我国业务数据环境,以MICAPS和GRIB1/GRIB2数据为主要输入源来实现自动化绘图的业务系统。MEPAS集成了多种物理量和对流参数的计算算法,在中尺度分析方面独具特色。MEPAS主要通过编写XML配置文件来模拟脚本,以命令行的方式运行,它学习简单,使用方便,运行稳定,出图高效,可用于业务系统的建设,也可用于气象科研,具有较高的应用推广价值。MEPAS通过模拟脚本实现自动绘图的技术可以被MICPAS借鉴或吸收,以填补MICAPS脚本交互的技术空白。     

Performance of the seasonal forecasting of the Asian summer monsoon by BCC_CSM1.1(m)

This paper provides a comprehensive assessment of Asian summer monsoon prediction skill as a function of lead time and its relationship to sea surface temperature prediction using the seasonal hindcasts of the Beijing Climate Center Climate System Model, BCC_CSM1.1(m). For the South and Southeast Asian summer monsoon, reasonable skill is found in the model's forecasting of certain aspects of monsoon climatology and spatiotemporal variability. Nevertheless, deficiencies such as significant forecast errors over the tropical western North Pacific and the eastern equatorial Indian Ocean are also found. In particular, overestimation of the connections of some dynamical monsoon indices with large-scale circulation and precipitation patterns exists in most ensemble mean forecasts, even for short lead-time forecasts. Variations of SST, measured by the first mode over the tropical Pacific and Indian oceans, as well as the spatiotemporal features over the Niño3.4 region, are overall well predicted. However, this does not necessarily translate into successful forecasts of the Asian summer monsoon by the model. Diagnostics of the relationships between monsoon and SST show that difficulties in predicting the South Asian monsoon can be mainly attributed to the limited regional response of monsoon in observations but the extensive and exaggerated response in predictions due partially to the application of ensemble average forecasting methods. In contrast, in spite of a similar deficiency, the Southeast Asian monsoon can still be forecasted reasonably, probably because of its closer relationship with large-scale circulation patterns and El Niño-Southern Oscillation.     

ENSO-independent contemporaneous variations of anomalous circulations in the Northern and Southern Hemispheres: The polar-tropical seesaw mode

Using the NCEP/NCAR reanalysis and the ENSO indices from the Climate Prediction Center over the period 1978–2014, we have investigated the contemporaneous circulation variations in the Northern and Southern Hemispheres by performing the singular value decomposition analysis of sea level pressure anomalies (SLPA) after the ENSO signal is regressed out. It is found that there exists a polar-tropical seesaw mode (PTSM) that characterizes with the out of phase fluctuations of SLPA between the polar and tropical regions in the Northern and Southern Hemispheres in boreal winter. This PTSM explains 47.74% of the total covariance of SLPA and is almost independent of ENSO. It demonstrates a long-term trend and oscillation cycles of 2–3 and 4–6 yr. The long-term trend in PTSM indicates that the sea level pressure gradually decreases in the tropics and increases in the polar region with time. This PTSM looks roughly symmetric about the equator besides the seesaw pattern of SLPA between the tropics and polar region in each hemisphere. The disturbances in the geopotential height field in association with the PTSM shows baroclinic features in the tropics whereas equivalent barotropic features in the mid and high latitudes in the troposphere. The anomalous thermal forcing in the tropical region is possibly one of the factors facilitating the formation of this PTSM. Significant global precipitation and temperature anomalies related to the PTSM are observed. In the positive PTSM phase, precipitation and temperature are higher than normal in southern Europe and the Mediterranean and surrounding areas, but lower than normal in northern Europe and Siberia. Precipitation is higher than normal while temperature is lower than normal in Northeast Asia. Significant temperature and precipitation anomalies possibly occur in the regions of western China, northern India, parts of North America, parts of subtropical Africa, Maritime Continent, and Antarctic. These results are helpful for better understanding of the circulation variations and the mechanisms behind the interactions between the Northern and Southern Hemispheres and the related winter climate anomalies over globe.     

A brief introduction to BNU-HESM1.0 and its earth surface temperature simulations

Integrated assessment models and coupled earth system models both have their limitations in understanding the interactions between human activity and the physical earth system. In this paper,a new human–earth system model,BNUHESM1.0,constructed by combining the economic and climate damage components of the Dynamic Integrated Model of Climate Change and Economy to the BNU-ESM model,is introduced. The ability of BNU-HESM1.0 in simulating the global CO2 concentration and surface temperature is also evaluated. We find that,compared to observation,BNU-HESM1.0underestimates the global CO2 concentration and its rising trend during 1965–2005,due to the uncertainty in the economic components. However,the surface temperature simulated by BNU-HESM1.0 is much closer to observation,resulting from the overestimates of surface temperature by the original BNU-ESM model. The uncertainty of BNU-ESM falls within the range of present earth system uncertainty,so it is the economic and climate damage component of BNU-HESM1.0 that needs to be improved through further study. However,the main purpose of this paper is to introduce a new approach to investigate the complex relationship between human activity and the earth system. It is hoped that it will inspire further ideas that prove valuable in guiding human activities appropriate for a sustainable future climate.     

登陆台风边界层风廓线特征的地基雷达观测

为了分析登陆台风边界层风廓线特征,利用2004—2013年中国东南沿海新一代多普勒天气雷达收集的17个登陆台风资料,采用飓风速度体积分析方法,反演登陆台风的边界层风场结构特征。与探空观测对比表明,利用雷达径向风场可以准确地反演登陆台风的边界层风场结构,其风速误差小于2 m/s,风向误差小于5°。所有登陆台风合成的边界层风廓线显示,在近地层(100 m)以上,边界层风廓线存在类似急流的最大切向风,其高度均在1 km以上,显著高于大西洋观测到的飓风边界层急流高度(低于1 km)。陆地边界层内低层入流强度也明显大于过去海上观测,这主要是由陆地上摩擦增大引起。越靠近台风中心,边界层风廓线离散度越大,其中,径向风廓线比全风速以及切向风廓线离散度更大。将风廓线相对台风移动方向分为4个象限,分析边界层风廓线非对称特征显示,台风移动前侧入流层明显高于移动后侧。最大切向风位于台风移动左后侧,而台风右后侧没有显著的急流特征,与过去理想模拟的海陆差异导致的台风非对称分布特征一致。     

MJO预报研究进展

热带大气季节内振荡 (Madden-Julian oscillation,MJO) 是次季节-季节时间尺度气候变率的支配模态。它不仅对低纬度地区天气气候产生重要影响,还能够通过经向传播和激发大气遥相关波列对中高纬度地区产生影响,是延伸期尺度最重要的可预报性来源。因此,MJO预报是次季节-季节气候预测中极为重要的部分,近年来受到国际学术界广泛关注。该文回顾了MJO预报发展历史,概述了当前国际上主要科研业务机构的MJO预报发展现状。目前基于统计方法和气候模式的MJO预报研究取得了较大进展,特别是多个耦合气候模式和一种基于时空投影方法的统计模型均能够显著提升MJO预报技巧 (有效预报可达20 d以上)。该文还介绍了中国气象局国家气候中心在MJO预报技术发展和业务系统研制方面的新进展,当前基于第2代大气环流模式的MJO业务预报填补了国内空白,技巧为16~17 d,而耦合气候模式试验的技巧已达到约20 d。总体来看,利用耦合模式预报MJO是未来发展的主要方向,其中,面向MJO的模式初始化和集合预报新方法研究将是关注重点。     

强对流天气监测预报预警技术进展

强对流天气预报业务包括监测、分析、预报、预警和检验等方面。对流初生识别、对流系统强度识别和对流天气类型识别等监测技术取得新进展,综合多源资料的监测技术已应用于中国气象局中央气象台业务。对流系统的触发、发展和维持机制等获得了新认识,我国不同类型强对流天气及其环境条件统计气候特征、分析规范及相应业务产品等为业务预报提供了必要基础和技术支撑。光流法、多尺度追踪技术以及应用模糊逻辑方法的临近预报技术等有明显进展,融合短时预报技术得到广泛应用,对流可分辨高分辨率数值 (集合) 预报及其后处理产品预报试验取得了显著成效,基于数值 (集合) 预报应用模糊逻辑方法的分类强对流天气短期预报技术为业务预报提供了技术支撑。强对流天气综合监测和多尺度自适应临近预报技术、多尺度分析技术以及融合短时预报技术、发展并应用模糊逻辑等方法的、基于高分辨率数值 (集合) 模式的区分不同强度等级和极端性的分类强对流天气精细化 (概率) 预报技术等是未来发展的主要方向。