用时钟方波测试地震数采时间精度及系统特性

用采集时钟方波信号加以分析的方法评估地震数据采集器的授时、守时服务精度、稳定性及系统特性。将具有时钟误差日志记录的数采的时间精度测试结果与日志记录相比较,二者完全一致;用时钟方波信号实测的数采经验传递函数与用厂家提供的滤波器系数并校正滤波器时间延迟计算的理论频率特性相符。实测结果显示,由于数采守时误差变化呈非线性,即使同一型号的不同数采间,其守时能力也可以差别很大;对于不同的数采及抽取滤波器,由于滤波延迟时间校正的参考点不一致,可导致数采记录数据的时间服务存在1个采样点左右的时间差,这对时间精度要求高的研究工作是不能接受的。     

An intermediate coupled model for the tropical ocean-atmosphere system

An intermediate ocean-atmosphere coupled model is developed to simulate and predict the tropical interannual variability. Originating from the basic physical framework of the Zebiak-Cane(ZC) model, this tropical intermediate couple model(TICM) extends to the entire global tropics, with a surface heat flux parameterization and a surface wind bias correction added to improve model performance and inter-basin connections. The model well reproduces the variabilities in the tropical Pacific and Indian basins. The simulated El Ni?o-Southern Oscillation(ENSO) shows a period of 3–4 years and an amplitude of about 2°C, similar to those observed. The variabilities in the Indian Ocean, including the Indian Ocean basin mode(IOBM) and the Indian Ocean Dipole(IOD), are also reasonably captured with a realistic relationship to the Pacific. However, the tropical Atlantic variability in the TICM has a westward bias and is overly influenced by the tropical Pacific. A 47-year hindcast experiment using the TICM for the period of 1970–2016 indicates that ENSO is the most predictable mode in the tropics. Skillful predictions of ENSO can be made one year ahead, similar to the skill of the latest version of the ZC model, while a "spring predictability barrier" still exists as in other models. In the tropical Indian Ocean, the predictability seems much higher in the west than in the east. The correlation skill of IOD prediction reaches 0.5 at a 5-month lead, which is comparable to that of the state-of-the-art coupled general circulation models. The prediction of IOD shows a significant "winter-spring predictability barrier", implying combined influences from the tropical Pacific and the local sea-air interaction in the eastern Indian Ocean. The TICM has little predictive skill in the equatorial Atlantic for lead times longer than 3 months, which is a common problem of current climate models badly in need of further investigation.     

Roles of different physical processes in upper ocean responses to Typhoon Rammasun (2008)-induced wind forcing

This study investigates the roles of different physical processes in the oceanic response to tropical cyclones(TCs) in the Pacific, using an ocean general circulation model with several numerical experiments. A case study is focused on Typhoon Rammasun, which passed through the northwestern tropical Pacific in May 2008. TC-induced wind stress fields are extracted using a locally-weighted regression(Loess) method from a six-hourly Cross-Calibrated Multi-Platform satellite scatterometer wind product. By comparing model experiments with TC wind forcing being explicitly included or not, the effects of TC on the ocean are isolated in a clean way. The local oceanic response is characterized by a cooling in the surface layer that persists along the typhoon track as a cold wake, and a deepening of the mixed layer(ML). The TC-induced wind can affect the ocean through the momentum effects, the ML processes(the stirring effect on the ML depth), and heat flux(via wind speed), repectively.Analyses of numerical experiments with these different underlying processes explicitly represented or not indicate that vertical mixing and upwelling are dominant processes responsible for surface cooling, while the surface heat flux also plays a nonnegligible role. Specifically, vertical mixing, upwelling and surface heat flux account for respectively ～53%, ～31% and ～16% of the sea surface temperature cooling. However, for the ML response, the vertical mixing and surface heat flux are dominant processes for the ML deepening, while the contribution from upwelling process is negligible. This study provides new insights into how TC-indcued wind forcing affects the ocean by isolating each different individual process in a clear way, which differs from previous direct heat budget analyses.     

Mechanisms of shelf-break frontogenesis

The shelf-break front is an omnipresent phenomenon in coastal oceans all over the world, but there is still no definitive explanation for the genesis of such a front. It is possible that different mechanisms are operative at different times and locations, but all of them should have something to do with the sharp change of bottom topography near the shelf-break. A couple of recently proposed mechanisms of shelf-break frontogenesis are dicussed. One of them invokes a flow convergence produced by local air-sea interac- tion over sloping topography, whereas the other relies on the depth dependence of wind-induced shear dispersion. These novel ide- as are based on new observational evidences and previous theoretical studies, and they are demonstrated here using an idealized o- cean-atmosphere coupled model and a stand-alone ocean model. The air-sea interaction mechanism seems plausible for the shelf- break front in the East China Sea, and the shear dispersion mechanism is likely to be applicable to the shelf-break front off the northcastem United States.     

GIS技术的研究现状及未来发展趋势

GIS是随着计算机技术发展而形成的一门新兴技术,其应用程度和范围也随之渗透、延伸,得到了人们的广泛关注。该文综述了地理信息的发展现状,从多个角度分析当前GIS技术发展存在的不足,并在此基础上研究分析了GIS技术的未来发展趋势。     

Preface to the Special Issue on Antarctic Meteorology and Climate:Past,Present and Future

The Antarctic,including the continent of Antarctica and the Southern Ocean,is a critically important part of the Earth system.Research in Antarctic meteorology and climate has always been a challenging endeavor.Studying and predicting weather patterns in the Antarctic are important for understanding their role in local-to-global processes and facilitating field studies and logistical operations in the Antarctic(e.g.,Walsh et al.,2018).Studies of climate change in the Antarctic are comparatively neglected compared to those of the Arctic.However,significant climate changes have occurred in the Antarctic in the past several decades,i.e.,a strong warming over the Antarctic Peninsula even with a recent minor cooling,a deepening of the Amundsen Sea low,a rapid warming of the upper ocean north of the circumpolar current,an increase of Antarctic sea ice since the late 1970s followed by a recent rapid decrease,and an accelerated ice loss from the Antarctic ice shelf/sheet since the late 1970s(e.g.,Turner et al.,2005;Raphael et al.,2016;Sallée,2018;Parkinson,2019;Rignot et al.,2019).Investigating recent climate change in the Antarctic and the underlying mechanisms are important for predicting future climate change and providing information to policymakers.     

国家地震烈度速报与预警工程建设进展

2010年1月,中国地震局启动国家地震烈度速报与预警工程项目立项建议书编制工作,2015年经国务院常务会议同意后获批,历经可行性研究、初步设计等,于2018年启动项目建设,并计划2023年投入运行,开展试服务。随着项目的实施,在台站观测系统建设、中心建设与集成、定制化软件研发、服务系统建设与拓展等方面取得重要进展。本文结合预警工程的目标、主要内容、技术体系等情况,对预警工程进展进行了介绍,随着项目的建设,部分地区已经开始对外开展地震预警试服务工作,工程完成后将成为我国防震减灾事业核心业务系统。     

海浪对北太平洋海-气二氧化碳通量的影响

利用4种海-气界面气体传输速率公式对比研究了北太平洋气体传输速率及其CO₂通量的季节变化特征。与单纯依赖风速的算法相比, 考虑波浪影响的气体传输速率和CO₂通量在空间分布和季节变化上具有明显差异。在低纬度地区(0°～30°N), 波浪参数使气体传输速率下降, 海洋对大气CO₂的吸收减少, 而在30°N以北范围内则出现新的气体传输速率高值区, 海洋对大气的吸收增加。进一步研究了黑潮延伸体区域的气候态月平均气体传输速率和CO₂通量。结果表明, 该区域气体传输速率和CO₂通量最大值分别出现于冬季和春季, 引入波浪参数后, 虽然该区域气体传输速率和CO₂通量平均值没有明显差异, 但季节变化强度显著增强。     

遥感卫星的防震减灾应用研究

整理了遥感卫星的发展历程和发展趋势,总结了目前国内外遥感卫星的特点、卫星遥感数据的现状及其应用于防震减灾领域的前景。在此基础上,研究卫星遥感应用于防震减灾的优势、面临的困难和目前的现状,并深入分析了卫星遥感数据应用于汶川地震救灾的成就和不足。最后对进一步推动卫星遥感的防震减灾应用展开了分析和讨论。