低温雨雪过程的粒子群-神经网络预报模型

利用逐日气温和降水量数据、NCEP/NCAR再分析资料以及预报场资料,通过分析提取我国南方区域持续性低温雨雪过程及其预报因子,使用粒子群-神经网络方法建立非线性的统计集合预报模型 (PSONN-EPM),对我国南方区域持续性低温雨雪过程进行预报试验。结果表明:以过程的冷湿程度及影响范围为标准,将低温雨雪过程分为一般过程和严重过程,并建立不同的预报模型效果较好。通过10 d独立样本预报试验看,基于粒子群-神经网络方法建立的集合预报模型比基于逐步回归方法建立的预报模型的预报平均相对误差小,对严重过程预报能力高于对一般过程预报,且这种非线性统计集合建模方法在建模过程中不需要调整神经网络参数,在实际预报业务中值得尝试。     

藏北龙木错—双湖—澜沧江板块缝合带发现晚石炭世—早二叠世洋岛型岩石组合

天泉群岛出露于龙木错—双湖—澜沧江板块缝合带的中西段,也是目前该缝合带上所发现的第一套洋岛型岩石组合。通过野外踏勘、剖面测制等对天泉群岛进行了较为详细的研究,结果显示,天泉群岛由9个孤立、岩石组合不同的洋岛组成,其中独泉沟洋岛、屏风岭洋岛的洋岛组分齐全,见玄武岩、灰岩、砾岩、硅质岩等,其他洋岛的洋岛组分不全。天泉群岛与展金组复理石沉积为整合接触,表明其形成时代为晚石炭世—早二叠世。天泉群岛的厘定,说明龙木错—双湖—澜沧江大洋在晚石炭世—早二叠世仍具有成熟的洋壳。该项研究进一步丰富了龙木错—双湖—澜沧江板块缝合带的演化内容,为反演区域地质演化历史提供了依据。     

中强地震前山东地下流体地震前兆模糊分维特征研究

采用模糊集理论与分形理论相结合的模糊分维方法，计算山东地下流体在１９８３年菏泽５．９级地震和１９９５年苍山５．２级地震前的变化。分析结果认为，模糊分维值反映了地震前兆时序观测资料的结构变化特征，具有一定的物理意义，为从复杂的地下流体前兆观测值中提取地震异常信息提供了新的方法，但对某些台、测项而言、必须具体分析其模糊分维变化特征及其震前异常变化特征。     

北京地区城市热岛强度长期变化特征及气候学影响机制

选择北京地区为研究区,基于1967~2016年城市站（北京站）和城郊农村站（密云站）的长期气象观测数据,研究平均气温、最高气温、最低气温对应的城市热岛强度长期变化特征及其气候学影响机制。研究发现,过去50 a平均气温和最低气温对应的城市热岛强度显著增加,增温率分别为0.29℃/10a和0.45℃/10a,而最高气温对应的城市热岛强度则没有明显变化趋势;统计分析显示过去50 a北京地区相对湿度、风速和日照时数显著降低以及气温显著上升有利于城市热岛的形成,强化城市热岛强度;未来全球变暖和快速城市化背景下北京地区城市热岛效应将进一步加剧,形成更频繁和持续时间更长的夏季城市高温热浪,严重危及城市居民生产生活和生命健康。     

Diagnostics of subseasonal prediction biases of the Asian summer monsoon by the NCEP climate forecast system

Biases of subseasonal prediction of the Asian summer monsoon are diagnosed using daily data from the hindcasts of 45-day integrations by the National Centers for Environmental Prediction Climate Forecast System version 2. The retrospective forecasts often show apparent systematic biases, which are mostly represented by the underestimation of the whole Asian monsoon. Biases depend not only on lead time, but also on the stage of monsoon evolution. An abrupt turning point of bias development appears around late June and early July, when ensemble spread and bias growth of winds and precipitation show a significant change over the northwestern Pacific (NWP) and the South Asian summer monsoon (SASM) region. The abrupt turning of bias development of winds, precipitation, and surface temperature is also captured by the first two modes of multivariate empirical orthogonal function analysis. Several features appear associated with the abrupt change in bias development: the western Pacific subtropical high (WPSH) begins its first northward jump and the surface temperature over the Tibetan Plateau commences a transition from warm bias to cold bias, and a reversal of surface temperature biases occurs in the eastern tropical Indian Ocean and the SASM region. The shift of WPSH position and the transition of surface thermal bias show close relationships with the formation of bias centers in winds and precipitation. The rapid growth in bias due to the strong internal atmospheric variability during short leads seems to mainly account for the weak WPSH and SASM in the model. However, at certain stages, particularly for longer-lead predictions, the biases of slowly varying components may also play an important role in bias development of winds and precipitation.     

Possible climate change/variability and human impacts,vulnerability of drought-prone regions,water resources and capacity building for Africa

ABSTRACT

This review article discusses the climate, water resources and historical droughts of Africa, drought indices, vulnerability, impact of global warming and land use for drought-prone regions in West, southern and the Greater Horn of Africa, which have suffered recurrent severe droughts in the past. Recent studies detected warming and drying trends in Africa since the mid 20th century. Based on the Fourth Assessment Report of the Intergovernmental Panel on Climate Change and the Coupled Model Intercomparison Project Phase 5 (CMIP5), both northern and southern Africa are projected to experience drying, such as decreasing precipitation, runoff and soil moisture in the 21st century and could become more vulnerable to the impact of droughts. The daily maximum temperature is projected to increase by up to 8°C (RCP8.5 of CMIP5), precipitation indices such as total wet day precipitation (PRCPTOT) and heavy precipitation days (R10 mm) could decrease, while warm spell duration (WSDI) and consecutive dry days (CDD) could increase. Uncertainties of the above long-term projections, teleconnections to climate anomalies such as ENSO and the Madden-Julian Oscillation, which could also affect the water resources of Africa, and capacity building in terms of physical infrastructure and non-structural solutions are also discussed. Given that traditional climate and hydrological data observed in Africa are generally limited, satellite data should also be exploited to fill the data gap for Africa in the future.

Editor D. Koutsoyiannis; Associate editor N. Ilich     

厦门浔江湾小型底栖生物数量分布及生态意义

本文首次报道 1 998年 5月厦门浔江湾水域 5个测站小型底栖生物调查的初步结果。小型底栖动物的平均密度为 5 9.6 5个 /cm2 ,自由生活的海洋线虫是优势类群 ,占总密度的 89.2 8% ;其次 ,底栖桡足类占 2 .76 % ;其它类群所占比例较少。小型底栖生物的丰度分布为湾口区底 ,湾中部高。文中分析了小型底栖生物具有高类群优势度和低类群多样性特征 ,以及线虫与桡足类的丰度比率与环境的关系 ,提出浔江湾水域环境状况应引起重视。     

白天工作条件下大气激光雷达探测的实验研究

作者在已完成大气激光雷达系统夜间工作的基础上 ,对白天工作条件下的各种环境背景光的干扰进行了理论与实验分析 ,得出太阳直射光和天空光为白天工作的主要背景干扰。实验结果表明 ,经过激光发射与接收视场角严格匹配及使用干涉滤光器 (2 .6 nm和 0 .15nm)进行窄带滤波 ,背景干扰被明显地剔除 ,可进一步压低背景干扰约 2 0倍。证明采取视场匹配及干涉滤光器的措施可基本保证激光雷达系统在白天条件下工作。     

包头地区二次大雪过程的成因分析

文章应用常规资料,从天气环流形势演变、物理量等方面,对2000年1月10—11日包头地区普降大雪过程作了客观的分析,揭示了大雪过程的发生、发展机制,对今后分析大雪过程具有一定指导意义。     

Comparison of short-term toxicity of 14 common phycotoxins (alone and in combination) to the survival of brine shrimp Artemia salina

Toxic harmful algal blooms(HABs) can cause deleterious effects in marine organisms, threatening the stability of marine ecosystems. It is well known that different strains, natural populations and growth conditions of the same toxic algal species may lead to different amount of phycotoxin production and the ensuing toxicity. To fully assess the ecological risk of toxic HABs, it is of great importance to investigate the toxic effects of phycotoxins in marine organisms. In this study, the short-te...