Calculation of geomagnetically induced currents (GIC) in a high-voltage electric power transmission system and estimation of effects of overhead shield wires on GIC modelling     

《Journal of Atmospheric and Solar》2007,69(12):1305-1311

Geomagnetically induced currents (GIC) flowing in ground-based technological networks, such as electric power transmission grids, are the ground end of the space weather chain originating from the Sun. GIC constitute a possible source of problems to the system. Matrix formulas enabling the calculation of GIC in a power grid have been presented before. In this paper, we summarise the formulas and also express them in an alternative form that includes the (geo)voltages driving GIC during a space weather event more explicitly. An issue usually ignored in GIC modelling is the effect of overhead shield wires protecting a power grid and generally earthed at the towers. By numerical examples, it is shown in this paper that such neglect causes an insignificant error in comparison with other inaccuracies involved in GIC modelling and is thus really acceptable in practice.  相似文献   

山东省极端强降水天气概念模型研究   总被引：4，自引：0，他引：4       下载免费PDF全文

侯淑梅  盛春岩  万文龙  韩永清 《大气科学学报》2014,37(2):163-174

利用山东省1971—1999年逐日降水资料,采用百分位法确定各站极端强降水阈值。据此阈值,在2000—2009年中挑选了39个极端强降水天气过程并进行天气分型,得到高空槽类、副高外围类、切变线类、气旋类、热带气旋类5类极端强降水概念模型。研究表明:切变线类、气旋类和热带气旋类暴雨区范围较大,而高空槽类和副高外围类暴雨区范围较零散;5类极端强降水均伴有低空急流,暴雨区一般位于700 hPa与850 hPa切变线(或槽线)之间、低空急流左侧风向风速辐合处;高空槽类、副高外围类、切变线类一型和气旋类均有冷空气影响,暴雨区位于850 hPa冷温度槽前部;5类极端强降水的产生机制不同,落区与θse的配置也不尽相同。  相似文献   

Frost-free season lengthening and its potential cause in the Tibetan Plateau from 1960 to 2010   总被引：1，自引：0，他引：1  

Dan Zhang  Wenhui Xu  Jiayun Li  Zhe Cai  Di An 《Theoretical and Applied Climatology》2014,115(3-4):441-450

Frost-free season was an important index for extreme temperature, which was widely discussed in agriculture and applied meteorology research. The frost-free season changed, which was associated with global warming in the past few decades. In this study, the changes in three indices (the last frost day in spring, the first frost day in autumn, and the frost-free season length) of the frost-free season were investigated at 73 meteorological stations in the Tibetan Plateau from 1960 to 2010. Results showed that the last frost day in spring occurred earlier, significantly in 39 % of the 73 stations. For the regional average, the last frost day in spring occurred earlier, significantly at the rate of 1.9 days/decade during the last 50 years. The first frost day in autumn occurred later, significantly in 31 % of the stations, and the regional average rate was 1.5 days/decade from 1960 to 2010. The changing rate of the first frost day in autumn below 3,000 m was 1.8 times larger than the changing rate above 3,000 m. In addition, the first frost day in autumn above 3,000 m fluctuated dramatically before the early 1990s and then it was later sharply after the early 1990s. The frost-free season length increased significantly at almost all stations in the Tibetan Plateau from 1960 to 2010. For the regional average, the frost-free season lengthened at the rate of 3.1 days/decade. The changing rate of the frost-free season length below 3,000 m was more significant than the changing rate above 3,000 m. Eight indices of large-scale atmospheric circulation were employed to investigate the potential cause of the frost-free season length change in the Tibetan Plateau during the past 50 years. There was a significant relationship between the frost-free season length and the Northern Hemisphere Polar Vortex indices. The weakening cold atmospheric circulation might be an essential factor to the Tibetan Plateau warming since 1960.  相似文献   

利用机载探测设备研究云中零度层附近云雷达反射率与液态含水量的关系          下载免费PDF全文

王烁  张佃国  郭学良  崔雅琴  樊明月  刘泉 《山东气象》2020,40(2):103-112

利用机载Ka波段云雷达（an airborne Ka-band Precipitation cloud Radar, KPR）与DMT （Droplet Measurement Technologies）粒子测量系统对山东一次积层混合云进行同步穿云观测。对获取的KPR资料进行飞行轨迹误差订正和数据插值处理,与DMT粒子测量系统计算的云中的液态含水量进行相关性研究。从试验飞行云层中选取了两段云区,共划分成9个时段（累计飞行18 min）展开讨论,其中有3个时段相关性比较好,相关系数超过0.7,并且利用相关系数最大的时段拟合出KPR反射率与云中液态含水量之间的关系式。针对每个时段的粒子特征参数、云滴谱型、冰晶谱型及典型粒子图像展开详细分析,结果表明,较强相关性时段内,大云滴浓度要高于小云滴,且观测粒子多为小于100 μm的小粒子;较弱相关性时段,CIP（Cloud Imaging Probe）探头观测到的粒子多为针状或板状冰晶,尺度为毫米量级。  相似文献   

2007—2019年山东省短时强降水时空分布特征          下载免费PDF全文

赵海军  曹洁  潘玲  王庆华  曹张驰  毛国荣 《山东气象》2021,41(2):149-155

选用山东 123 个国家级地面气象观测站 2007—2019 年地面逐小时降水资料,分析短时强降水分布特征,主要结论如下：1）其间共有 695 个短时强降水日、3 337 个短时强降水时次和 6 257 个短时强降水样本,基于排序法确定山东省极端短时强降水间值为 71.2 mm ? h-1,鲁东南地区间值最高,鲁中地区间值最低。2）各站年均发生 3.9 次短时强降水天气,鲁东南地区短时强降水和极端短时强降水发生频次最多,半岛地区短时强降水发生最少,鲁西南地区极端短时强降水发生最少。3）短时强降水集中出现在 6 月中旬至 8 月下旬,又以 8 月上旬最多。4）日变化显著,呈现典型 “双峰” 特征,主要集中在午后至傍晚,其次是后半夜;6 月中旬至 8 月下旬傍晚和后半夜发生短时强降水的可能性大,需重点关注。  相似文献   

Surge-type glaciers in Karakoram Mountain and possible catastrophes alongside a portion of the Karakoram Highway     

Ding  Minghu  Huai  Baojuan  Sun  Weijun  Wang  Yetang  Zhang  Dongqi  Guo  Xiaoyin  Zhang  Tong 《Natural Hazards》2018,90(2):1017-1020

Natural Hazards - Along the Karakoram Highway (KKH) region, glacier surge, avalanche and debris flow play a dominant role in these disasters. The data of surge-type glaciers along the KKH are...  相似文献   

Fractions and Bioavailability of Soil Inorganic Phosphorus in the Loess Plateau of China under Different Vegetations   总被引：1，自引：0，他引：1  

WEI Xiaorong  SHAO Mingan  SHAO Hongbo  GAO Jianlun  XU Gang 《《地质学报》英文版》2011,85(1):263-270

Plants play an important role in soil phosphorus nutrition. However, the effect of plants on phosphorus nutrition in soils of the Loess Plateau of China is not well understood. This study was conducted to reveal the relationships between plants and phosphorus’ fractions and availability in the Loess Plateau of China. Twenty-two plant communities were surveyed and soil samples under different plant canopies were collected for the determination of soil properties and inorganic phosphorus fractionation. The results showed that Leguminosae and Lilaceae reduced pH and increased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies, while Labiatae and Rosaceae increased pH and decreased organic matter, cation exchange capacity, total and Olsen phosphorus in soils under their canopies. The contents of Ca2P, Ca8P, Al-P and Fe-P were highly related with soil Olsen phosphorus. They were all higher in soils under Leguminosae and Lilaceae and lower in soils under Labiatae and Rosaceae. The results of this study indicate that Leguminosae and Lilaceae improved phosphorus nutrition in soils, yet Labiatae and Rosaceae impeded the improvement of phosphorus nutrition in soils under their canopies, which will be of more help to instruct vegetation restoration in the region and provide information for soil development.  相似文献   

WRF模式物理参数化方案对一次局地大暴雨预报的影响研究          下载免费PDF全文

盛春岩  荣艳敏  曲巧娜  范苏丹 《山东气象》2020,40(1):66-78

基于WRF(Weather Research and Forecasting)模式及其3Dvar(3-Dimentional Variational)资料同化系统,采用36、12、4 km嵌套网格进行快速更新循环同化和不同的微物理及积云对流参数化方案对比试验,对2011年5月8日鲁中一次局地大暴雨过程进行了研究。结果表明,快速更新循环同化地面观测资料是影响模式降水落区预报准确性的关键因素,不同的微物理和积云对流参数化方案主要影响降水强度预报。采用不同的微物理参数化方案和积云对流参数化方案进行降水预报对比试验表明,LIN方案和WSM6(WRF Single-Moment 6-class)微物理参数化方案对降水预报均较好,LIN方案降水预报较WSM6方案略强。4 km网格预报使用K-F (Kain-Fritsch)积云对流参数化方案或不使用积云对流参数化方案,预报的降水均较好。4 km网格使用旧的K-F积云对流参数化方案,预报的近地层大气风场偏弱,导致大气动力抬升作用偏弱,从而造成模式降水预报偏弱。  相似文献   

雾与能见度数值预报诊断SW方案和FSL方案改进的研究及评估          下载免费PDF全文

夏凡  李昌义  刘诗军  王夏添 《山东气象》2020,40(3):48-59

为了提高雾与能见度的预报水平,对业务上常用的两种能见度诊断方案,即Stoelinga and Warner（SW）方案与Forecast Systems Laboratory（FSL）方案的改进进行预报试验,SW方案基于Gultepe方案考虑了液态水粒子数浓度对能见度的影响,FSL改进方案中利用了递减平均法对公式中用到的温度与露点温度进行订正,并用其重新计算公式中的相对湿度。基于山东省气象科学研究所逐时更新循环（hourly update cycle,HUC）业务模式输出结果,从2015—2016年选取10次雾天气过程,并详细分析了2015年11月13—14日这次雾天气过程的预报结果,比较了改进前后各方案对雾与能见度的预报效果,结果显示：在模式预报的雨水含量占总液态含水量比例较大的预报时效,改进后的SW方案对雾与能见度预报效果优于原始方案,在模式预报液态含水量接近0的预报时效,改进前后的SW方案对雾与能见度的预报效果相当;利用订正的温度与露点温度重新计算相对湿度,其平均绝对误差（mean absolute error,MAE）降低明显的预报时段,改进后的FSL方案对雾与能见度的预报效果大大提升。将两种改进后的方案相融合并进行预报试验,结果显示,综合对能见度与雾的预报效果,Combined Visibility（CVIS）方案要优于其他两种改进方案。  相似文献   

概率匹配平均法在山东强降水预报中的应用          下载免费PDF全文

荣艳敏  盛春岩  范苏丹  曲巧娜 《山东气象》2017,37(3):95-101

基于WRF集合预报系统开发了概率匹配平均降水产品,选取了山东省2014—2016年共13次强降水过程,检验评估了概率匹配平均法在山东省强降水预报中的综合表现。结果表明：对于不同的强降水过程,各预报产品的预报能力差异较大,尤其是对暴雨以上量级降水的预报存在较大偏差;概率匹配平均相对集合平均,对大雨以上量级降水预报有明显改善,较WRF确定性预报产品也有一定提高,对强降水预报具有一定指示意义;该方法的改进主要体现在对不同量级降水的调整上,尤其是强降水的落区,相对集合平均增大了强降水的范围和强度,但对整个区域的总降水量预报没有很好的改进作用。  相似文献