Can the Tibetan Plateau snow cover influence the interannual variations of Eurasian heat wave frequency?   总被引：6，自引：0，他引：6  

Zhiwei Wu  Peng Zhang  Hua Chen  Yun Li 《Climate Dynamics》2016,46(11-12):3405-3417

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“灿鸿”台风造成浙江东北部大暴雨成因分析   总被引：2，自引：1，他引：1  

周福  钱燕珍  方艳莹  顾小丽  王毅 《气象》2016,42(3):305-313

本文利用常规观测和自动站加密资料、卫星云图资料及NCEP再分析资料,分析了2015年7月10—11日1509号台风灿鸿造成其西侧浙江东北部异常强暴雨事件,得到本次大暴雨过程是由于"灿鸿"强度强、范围大、直接影响时间长,长时间东北气流下,在浙东北特殊地形作用下,形成地面辐合带造成的。台风影响前期该区域处在对流不稳定状态,水汽含量丰沛,低层辐合,高层辐散且气温低,有利于上升运动,上层水汽冷凝造成强降雨。暴雨区低层MPV1由负值转变为正值,导致垂直涡度加强,925 hPaθ_(se)的高能区的长期存在,有利于上升气流增强,水汽长时间大量输送有利于台风的发展和维持,也有利于强降雨的形成。这些物理量的变化与雨量增大和减小有6~12 h的提前。呈喇叭口状的杭州湾及南面四明山、狭长东北一西南走向的象山港以及南岸的山脉等地形有迎风坡作用和地形辐合,对东北气流参与造成的降雨有增幅作用。  相似文献   

Effects of optimized root water uptake parameterization schemes on water and heat flux simulation in a maize agroecosystem          下载免费PDF全文

Fu Cai  Huiqing Ming  Na Mi  Yanbing Xie  Yushu Zhang  Rongping Li 《Acta Meteorologica Sinica》2017,31(2):363-377

As root water uptake (RWU) is an important link in the water and heat exchange between plants and ambient air, improving its parameterization is key to enhancing the performance of land surface model simulations. Although different types of RWU functions have been adopted in land surface models, there is no evidence as to which scheme most applicable to maize farmland ecosystems. Based on the 2007–09 data collected at the farmland ecosystem field station in Jinzhou, the RWU function in the Common Land Model (CoLM) was optimized with scheme options in light of factors determining whether roots absorb water from a certain soil layer (W_x) and whether the baseline cumulative root efficiency required for maximum plant transpiration (W_c) is reached. The sensibility of the parameters of the optimization scheme was investigated, and then the effects of the optimized RWU function on water and heat flux simulation were evaluated. The results indicate that the model simulation was not sensitive to W_x but was significantly impacted by W_c. With the original model, soil humidity was somewhat underestimated for precipitation-free days; soil temperature was simulated with obvious interannual and seasonal differences and remarkable underestimations for the maize late-growth stage; and sensible and latent heat fluxes were overestimated and underestimated, respectively, for years with relatively less precipitation, and both were simulated with high accuracy for years with relatively more precipitation. The optimized RWU process resulted in a significant improvement of CoLM’s performance in simulating soil humidity, temperature, sensible heat, and latent heat, for dry years. In conclusion, the optimized RWU scheme available for the CoLM model is applicable to the simulation of water and heat flux for maize farmland ecosystems in arid areas.  相似文献   

Optical properties of cirrus transition zones over China detected by CALIOP          下载免费PDF全文

Hongke Cai  Yunfei Fu  Quanliang Chen  Xiao Feng  Xin Tie  Ranting Tao  Kepiao Xu 《Acta Meteorologica Sinica》2017,31(3):576-585

A transition zone near cirrus lateral boundaries can be detected by CALIOP (cloud–aerosol lidar with orthogonal polarization). In the present study, for such transition zones over China, a number of optical properties, such as the backscatter coefficient and depolarization ratio, showed transitional characteristics between cirrus and clear sky. The stepped horizontal profile showed sharp changes in particle number and morphology between cirrus clouds and clear sky. The color ratio, however, was unable to show cirrus transition features because of the low signal-to-noise ratio. Typical ice particles presented a color ratio of 0.55–1.25 and a depolarization ratio of greater than 0.12, which were significantly higher than those of clear sky. Therefore, optical properties in transition took the form of stepwise horizontal profiles. The proportion of typical-featured particles also demonstrated a stepped horizontal profile similar to the optical characteristics, but the relationship between the proportion and the optical characteristics was not uniform in the cirrus clouds, transition zone, and clear sky. Therefore, the optical changes in the transition zone were caused by not only the change in particle concentration, but also the change in the particles themselves. The probability density distribution of the transition-zone widths showed a positive skewness distribution, and transition zones with widths of 3–5 km occurred most frequently. Overall, transition-zone width decreased with increasing temperature and increased with increasing vertical and horizontal wind speeds. This trend demonstrated independence with the direction of the vertical and horizontal winds. These observations implied that the transitional features were caused by material exchange, such as entrainment and turbulent transport, near the cirrus lateral boundaries, and by the phase transformation of particles, such as sublimation.  相似文献   

CINRAD/CD接收机疑难故障案例诊断分析     

陈士英  闫平  叶飞  王志伟  王庆有  张丽霞 《气象科技》2017,45(1):68-71

针对CINRAD/CD无机内测试信号的疑难故障案例,介绍如何借助大型电子设备规范化维修的理念和方法,结合雷达系统原理和信号流程,综合运用原理分析法、越级法、测量法、代替法等故障诊断方法进行分析与判断,逐步缩小故障排查范围,从而达到快速定位及排除故障的目的。最终确定该故障是由于接收与监控分机间的信号线断开,造成控制码没有送至微波组件内单刀双掷微波开关所导致的。文中提供了该类型故障的规范化维修流程,其诊断方法和思路可广泛应用于CINRAD技术保障工作中。  相似文献   

CLDAS数据质量在线评估系统的设计与实现     

李显风  师春香  胡佳军  韩帅  姜志伟 《气象科技》2017,45(6):1116-1124

数据质量评估是模式业务运行中重要环节。本文利用土壤水分观测数据和中国气象局陆面数据同化系统(CLDAS)产品数据,采用MySQL数据库和html、JavaScript、HighChart等Web技术,建立CLDAS数据质量在线评估系统。系统采用相关系数、均方根误差、相对偏差和平均偏差等统计指标,实现对任意站点及省份、任意时段、不同土壤层次的土壤湿度的评估分析,并以时间序列图,散点图等多种方式对比显示土壤湿度观测与模拟值。系统具备各类统计指标的实时计算,并通过Web页面实时展示评估结果,实现对模式产品的数据质量进行实时监视。  相似文献   

T639预报气温产品误差分析与订正     

李华  宫明晓  刘春涛  梁卫芳  付业理 《气象科技》2017,45(6):1065-1069

由于T639数值预报模式对具体区域预报有一定偏差,为了更好的利用该模式做出山东即墨本区域各自动站气温预报,制定订正方法,将订正方法运用到实际业务中,推广到相关单位,提高气温预报准确率,本文利用2013年1月至2015年12月山东省即墨市8个区域自动站的最高(低)气温实况和对应的T639数值预报24小时2m气温预报产品进行了日最高(低)气温的预报准确率、相对误差分析,并结合风向风速预报结论和地形分区,运用综合订正、季节订正、风向订正和风速订正4种误差订正方法,在对比检验的基础上,得出如下结论:在4种订正方法中,预报准确率最高为综合订正方法。  相似文献   

一种顾及电离层延迟信息的长基线北斗三频模糊度解算方法     

杨东森  吕志伟  丛佃伟  张伦东 《测绘科学技术学报》2017,34(3)

北斗卫星导航系统播发3个频点的导航信号,有利于载波相位模糊度解算。鉴于传统的三频模糊度解算方法由于受基线距离的限制难以在中长基线情形下可靠地固定模糊度,本文提出一种适用于北斗卫星系统中长基线模糊度固定的新方法。实验结果表明,改进的新算法不受基线长度的约束,在保证超宽巷、宽巷模糊度正确固定的同时,宽巷模糊度估值误差在0.3周以内;窄巷模糊度估值误差在3周以内。相比于传统算法,新方法的改进效果较好。  相似文献   

青藏高原湿地土壤冻结、融化期间的陆面过程特征   总被引：4，自引：0，他引：4       下载免费PDF全文

张海宏  肖宏斌  祁栋林  李甫 《Acta Meteorologica Sinica》2017,75(3):481-491

利用青藏高原中部玉树隆宝湿地2015年7月-2016年7月的观测资料,分析了土壤冻结、融化前后土壤温、湿度和地表能量收支特征,结果表明：冻土持续时期为12月至次年4月,深层土壤的冻结较浅层土壤滞后,融化过程快于冻结过程,5-40 cm土壤全部冻结历时51 d,全部融化历时19 d。土壤体积含水量年变化幅度达0.6 m³/m³。冻结过程5-40 cm土壤体积含水量下降,融化过程5-10 cm土壤体积含水量升高。土壤冻结之后,感热通量白天的值升高,潜热通量白天的值降低,净辐射和土壤热通量均降低,土壤热通量日变化幅度增大。土壤融化之后,潜热通量、净辐射和土壤热通量白天的值升高。地表反照率、鲍恩比、土壤热导率和土壤热扩散率冻结后增大融化后减小,土壤热容量冻结后减小融化后增大。  相似文献   

区域监测站与低轨卫星数据联合测定MEO卫星轨道     

王乐  张勤  黄观文  燕兴元  秦志伟 《测绘学报》2016,45(Z2):101-108

我国北斗二代系统(BDS)地面运控监测站数量较少且为区域分布,短期内难以实现全球建站,因此对全球运行的中圆地球轨道卫星(MEO)难以形成连续多重覆盖观测,导致BDS的MEO实时轨道精度偏低。基于上述问题,本文考虑到低轨卫星星载GNSS数据可以有效弥补区域监测站在空间覆盖及几何结构上的不足,设计了一种将星载GNSS接收机作为高动态天基监测站,联合地面区域监测站数据对卫星导航系统的MEO卫星轨道进行实时解算预报的方法。算例结果显示:7个区域监测站联合1至3个天基监测站,其定轨精度可分别提升约21%、34%和55%,这也表明,地面区域监测站联合天基低轨卫星数据可有效提高MEO卫星的轨道精度。建议我国BDS在区域测站分布阶段可采用联合低轨卫星数据方法提高北斗MEO卫星实时轨道精度。  相似文献