Recent Enhancement in Co-Variability of the Western North Pacific Summer Monsoon and the Equatorial Zonal Wind

The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the evolution of the El Niño-Southern Oscillation(ENSO).The possible linkage between the EZW over the western Pacific and the offequatorial monsoonal winds associated with the WNPSM and its decadal changes have not yet been fully understood.Here,we find a non-stationary relationship between the WNPSM and the western Pacific EZW,significantly strengthening their correlation around the late 1980s/early 1990s.This observed shift in the WNPSM–EZW relationship could be explained by the changes in the related sea surface temperature(SST)configurations across the tropical oceans.The enhanced influence from the springtime tropical North Atlantic,summertime tropical central Pacific,and maritime continent SST anomalies may be working together in contributing to the recent intensified WNPSM–EZW co-variability.The observed recent strengthening of the WNPSM–EZW relationship may profoundly impact the climate system,including prompting more effective feedback from the WNPSM on subsequent ENSO evolution and bolstering a stronger biennial tendency of the WNPSM–ENSO coupled system.The results obtained herein imply that the WNPSM,EZW,ENSO,and the tropical North Atlantic SST may be closely linked within a unified climate system with a quasi-biennial rhythm occurring during recent decades,accompanied by a reinforcement of the WNPSM–ENSO interplay quite possibly triggered by enhanced tropical Pacific–Atlantic cross-basin interactions.These results highlight the importance of the tropical Atlantic cross-basin influences in shaping the spatial structure of WNPSM-related wind anomalies and the WNPSM–ENSO interaction.

Structures and Characteristics of the Windy Atmospheric Boundary Layer in the South China Sea Region during Cold Surges

An observational analysis of the structures and characteristics of a windy atmospheric boundary layer during a cold air outbreak in the South China Sea region is reported in this paper. It is found that the main structures and characteristics are the same as during strong wind episodes with cold air outbreaks on land. The high frequency turbulent fluctuations （period 〈 1 min） are nearly random and isotropic with weak coherency, but the gusty wind disturbances （1 rain〈period 〈 10 min） are anisotropic with rather strong coherency. However, in the windy atmospheric boundary layer at sea, compared with that over land, there are some pronounced differences： （1） the average horizontal speed is almost independent of height, and the vertical velocity is positive in the lower marine atmospheric boundary layer; （2） the vertical flux of horizontal momentum is nearly independent of height in the low layer indicating the existence of a constant flux layer, unlike during strong wind over the land surface; （3） the kinetic energy and friction velocity of turbulent fluctuations are larger than those of gusty disturbances; （4） due to the independence of horizontal speed to height, the horizontal speed itself （not its vertical gradient used over the land surface） can be used as the key parameter to parameterize the turbulent and gusty characteristics with high accuracy.

Climate Projections of Spatial Variations in Coastal Storm Surges Along the Gulf of Mexico and U.S.East Coast

Using statistically downscaled atmospheric forcing, we performed a numerical investigation to evaluate future climate's impact on storm surges along the Gulf of Mexico and U.S. east coast. The focus is on the impact of climatic changes in wind pattern and surface pressure while neglecting sea level rise and other factors. We adapted the regional ocean model system(ROMS) to the study region with a mesh grid size of 7–10 km in horizontal and 18 vertical layers. The model was validated by a hindcast of the coastal sea levels in the winter of 2008. Model's robustness was confirmed by the good agreement between model-simulated and observed sea levels at 37 tidal gages. Two 10-year forecasts, one for the IPCC Pre-Industry(PI) and the other for the A1 FI scenario, were conducted. The differences in model-simulated surge heights under the two climate scenarios were analyzed. We identified three types of responses in extreme surge heights to future climate: a clear decrease in Middle Atlantic Bight, an increase in the western Gulf of Mexico, and non-significant response for the remaining area. Such spatial pattern is also consistent with previous projections of sea surface winds and ocean wave heights.

Seasonal Wind Characteristics and Prospects of Wind Energy Conversion Systems for Water Production in the Far North Region of Cameroon

This study aimed at investigating the characteristics of the wind power resource in the Far North Region of Cameroon (FNR), based on modelling of daily long-term satellite-derived data (2005-2020) and in-situ wind measurements data (1987-2020). Five different reliable statistical indicators assessed the accuracy level for the goodness-of-fit tests of satellite-derived data. The two-parameter Weibull distribution function using the energy factor method described the statistical distribution of wind speed and investigated the characteristics of the wind power resource. Six 10-kW pitch-controlled wind turbines (WT) evaluated the power output, energy and water produced. A 50 m pumping head was considered to estimate seasonal variations of volumetric flow rates and costs of water produced. The results revealed that the wind resource in FNR is suitable only for wind pumping applications. Based on the hydraulic requirements for wind pumps, mechanical wind pumping system can be the most cost-effective option of wind pumping technologies in FNR. However, based on the estimated capacity factors of selected WT, wind electric pumping system can be acceptable for only four out of twenty-one sites in FNR.

Summer’s Warm Surge in the North Pacific

A physical mechanism is proposed for initiation of summer’s warm surge, which is a large body of surface layer water, heated by the spring and summer sun, which moves north to mid- and high latitudes near the ocean’s center starting from the western tropical North Pacific. As the sun approaches the equator from the south during January to March, the surface layer warms and the sea level rises due to thermal expansion, creating a downward slope to the north of the sea surface. Warm surface water will therefore begin to move north assuming that there is no counterbalancing force. At some point the colder surface water to the north, being unstable, will move south and cause the warm surface layer in the south to move farther north than the sun can urge it to do. Summer’s warm surge is a transient and shallow thermal circulation that occurs every year. Measurements in the western tropics of the northward slope of the sea surface, and the northward surface flow, are needed to confirm the proposed hypothesis.

Analytical Solution for Evaluation of Voltage Surge Distribution along Transformer Windings through the Method of Residues

Computer programs have definitely become indispensable for designing power transformer. Among several applications, computer programs are mostly used for electric field calculation and thus electrical insulation concerns. In consequence, studies based on analytical approach to basic studies of correlated problems have become even more important because they form the very basis of knowledge that is necessary to every transformer designer in view of taking all the advantages of computational analyses. On the other hand, one of the most important basic studies consists in the evaluation of voltage surge distribution along transformer windings for which the method of separation of variables has been extensively used thanks to some simplifying assumptions. With this aim, authors have developed and previously published works that show the applicability of an alternative and useful analytical method that is the method of the residues, which requires no simplification to be assumed. In this work, another important step is taken towards proofing the total applicability of this promising method that is through a practical problem. A comparison to the numerical method TLM （transmission line method） is also performed and concordance with TLM and experimental data confirms the proposal of the method of residues can be also applicable to several others problems of electromagnetism.

风对波状涌潮海塘越浪水动力特性影响的数值研究

文章基于二维不可压缩两相流数值模型,首先通过对比数值计算结果与试验数据,验证了该两相流涌潮计算模型模拟波状涌潮与海塘相互作用的可靠性;然后通过设置合理的计算工况,系统分析了风速、涌潮高度、潮前水深和斜坡坡度对波状涌潮在海塘上的越浪水动力特性的影响。计算结果表明:向岸风速会显著影响波状涌潮的海塘越浪量,风速越大,涌潮的越浪量越大,且挡浪墙所受荷载也越大;随着涌潮高度和潮前水深的增大,涌潮越浪量和挡浪墙所受涌潮荷载也随之增大;当增大海塘斜坡坡度时,涌潮越浪量和挡浪墙所受涌潮荷载均呈现先增大后减小的趋势。

中国沿海地区热带气旋危险性分析

基于1980—2016年的西北太平洋热带气旋尺度资料,采用2种方法分析了热带气旋灾害的危险性。第一种方法根据热带气旋的风圈半径,用GIS生成了每个气旋的影响范围,对于登陆中国沿海的227个热带气旋,用叠加法得到了其影响范围与频次。第二种方法侧重热带气旋引发的风暴潮灾害,用潮位模型估算了热带气旋登陆时的潮位数据,提出了H3指标,该指标用潮位、风速和中心气压3个因子计算潮位点的风暴潮危险性,并根据H3指标得到了海岸线的危险性综合指标。分析结果表明,福建、广东两省受热带气旋的影响最为严重。37 a间,福建省有80%的面积(约9.8万km^(2))受热带气旋影响的频次超过20次;广东省则有70%的面积(约12.6万km2)受热带气旋影响的频次超过20次。受风暴潮危害大的海岸线主要位于广东、广西、福建、浙江四省,危险性指标在30以上的有广东的湛江市、茂名市、江门市、阳江市和珠海市;广西的北海市、防城港市和钦州市;福建的福州市以及浙江的台州市和温州市。

三大洋海温异常对2022年2月中国南方持续低温雨雪的影响

2022年2月,中国南方出现持续低温雨雪天气:区域平均降水量126.6 mm,较多年(1981~2020年)平均偏多99.7%;日最低气温5.1℃,较多年平均偏低2.6℃。分析表明,该地区700 hPa到925 hPa异常强的经向风垂直切变是2月持续低温雨雪期间的关键环流特征。经向风垂直切变与三大洋的海温异常均有联系:在赤道中东太平洋海温偏冷的背景下,热带西太平洋和北太平洋中部海温偏暖可导致东亚槽加深和对流层低层到近地面出现偏北风异常;北大西洋中部海温偏暖可通过西欧—东亚沿岸的北支Rossby波列加强乌拉尔山高压脊和东亚槽,使得西伯利亚高压和中国南方低层偏北风增强;东南印度洋海温偏暖有利于南支槽加深和西北太平洋异常反气旋加强,对流层中层偏南风加强。海温对环流的影响有明显的季内变化,北太平洋中部和北大西洋中部海温与西伯利亚高压仅在2月显著相关,有利于2月气温偏低;东南印度洋海温与1月和2月的南支槽显著相关,与2月西北太平洋异常反气旋显著相关,中国南方地区降水从1月中旬起增多可能与该海域海温持续偏暖有关。因此,上述三个海区的海温异常可能与2021/2022年冬季暖干到冷湿的季内转折以及2022年2月持续低温雨雪有关。

冬春两湖盆地地区大气气溶胶污染的年代际变化特征及其与东亚经向风南北反相位的联系

基于MERRA-2及ERA5逐月再分析资料,本文采用EOF分析、线性回归和合成分析等方法,分析了1980~2020年长江流域中游两湖盆地地区气溶胶光学厚度(AOD)的年代际变化特征及东亚经向风南北反位相模态对其的影响。结果表明,在年代际尺度上两湖盆地地区AOD呈现非线性的变化趋势,20世纪80、90年代处于低值,21世纪初AOD持续升高,2010年后开始下降。空间场上表现为全区一致的变化特征,高值区主要位于两湖盆地中部,以洞庭湖为中心呈南北纵向分布。进一步对两湖盆地AOD年代际变化与大气环流异常关系的分析表明,在东亚经向风南北反相模的影响下,偏北风输送是影响两湖盆地AOD年代际变化的主要气象原因。在年代际尺度上,当西伯利亚高压的强度、面积增大,东亚大槽西移,西北太平洋副热带高压脊线南移时,东亚经向风南北反相模趋于正相位(即长江以北有异常偏南风、长江以南有异常偏北风)。此时,两湖盆地位于气旋性环流异常的底部,在异常的偏北风的作用下,西北地区的气溶胶向两湖盆地输送加强。且两湖盆地处于两个异常气旋性环流的中间,气压梯度小,风速偏弱,使得两湖盆地气溶胶输入大于输出,促进21世纪初AOD年代际升高。

东亚夏季风与热带海气相互作用研究进展

在东亚夏季风变异的众多影响因子中,热带海温是影响夏季风系统变化的主要原因。近年来,国内外学者在热带海温异常对东亚夏季风影响的研究方面取得了很大进展。本文从季节内、年际到年代际时间尺度,简要回顾了近年来关于热带海气相互作用影响东亚夏季风变异及其机理的研究进展,特别综述了关于ENSO(El Ni?o-Southern Oscillation)、热带印度洋和大西洋海温异常对东亚夏季风系统的影响和机理方面的主要研究进展。此外,本文还系统回顾了热带海温对东亚夏季风与冬季风关联的影响及过程。最后,提出了在热带海温异常影响东亚夏季风季节内尺度变化、全球变暖下热带海温的变化及其对东亚夏季风的影响等方面值得深入探讨的科学问题。

卫星遥感北大西洋风暴“尤尼斯”生成和发展特征

2022年2月中旬,北大西洋冬季风暴“尤尼斯”(Eunice)给欧洲中、西部带来严重自然灾害。以卫星观测数据为主,研究了“尤尼斯”发生的环境场、卫星水汽图像干侵入特征、对流层中高层位涡强迫对爆发性发展的影响等。结果表明:“尤尼斯”活动期间,北半球高纬度西半球偏冷、东半球偏暖,极涡偏向北美大陆,北美极区附近平均气温偏低。“尤尼斯”的生成和北美极区附近极涡分裂南下的冷空气沿着西风带东传有关。爆发性发展期间,海平面气压下降率约40 hPa/(24 h),远超爆发性发展指标(24 hPa/(24 h)),且出现在海温正距平区。格陵兰岛南部气旋提供的极区冷空气对爆发性发展尤为重要,该冷空气在北大西洋洋面形成强西北风转偏西风,表现为排列整齐的大范围细胞状积云一直延伸至风暴中心附近,卫星水汽图像上表现为快速增强的干侵入特征,并伴有高位涡异常。发展至最强阶段,高位涡向下伸展,400 hPa最强高位涡区位于风暴中心的正上方,500 hPa以下高位涡向东南方向倾斜,并伴随着对流层中、下层强下沉运动,下沉运动为低空风速增强提供了一定的高空能量来源,高位涡侵入的下方也有利于低层气旋式环流发展。

浙江沿海风暴潮增水对台风移速的响应研究

基于MIKE21建立东中国海-浙江沿海嵌套潮流模型,采用修正的Holland风场对1509号台风“Chanhom”产生的风暴潮进行模拟,通过与实测数据对比验证表明该模型模拟结果合理可靠。基于验证模型,对1949—2020年间2个极端移速台风(低移速台风“Mary”和高移速台风“Kai-tak”)进行模拟分析,为剥离单一移速变量对增水的影响,以1509号台风“Chan-hom”为基础,设置3种台风移速(2倍移速、实际移速及50%移速)对风暴潮增水影响进行研究,得到如下结论:(1)低移速台风尽管登陆时强度低于高移速台风,但对浙江沿海海域的增水影响时间更长,台风“Kai-tak”增水0.5 m及以上的持续时间仅4 h,而“Mary”却长达12 h;(2)台风移速越慢,向岸风影响时间越长,舟山群岛以西至钱塘江海域的增水随着移速的减小呈上升趋势,杭州湾南岸具有较大洪水及内涝隐患;(3)在台风登陆点朱家尖,3种移速下的增水及风速相差不大,最大增水出现在台风登陆前风速最大时刻,而在舟山外海,增水大小受潮位波动影响呈现周期变化,低潮位时增水较大,高潮位时增水较小。

近代齐鲁名医张伯龙中风学术思想探析

张伯龙是近代齐鲁名医,与张锡纯、张山雷并称“近代三张”。张伯龙博采历代医家学术精华,辨析了中风病名源流,汇通中西理论,探讨了中风病理机制,提出中风病位在脑,重视以脉测证、凭脉施治,确立了“潜阳息风,镇摄肝肾”的治疗大法,强调南北分治,注重调理体质预防中风。张伯龙的中风学术思想推动了清末民初中风理论与实践的发展,开辟了近现代中风研究的新路径。

重复脉冲法在凸极转子绕组匝间短路检测中的应用探索

为了探索和推广重复脉冲检测法(RSO)在大型凸极式转子绕组匝间短路检测中的应用,参考在隐极发电机中的应用情况和经验,采取控制变量法,对某大型水轮发电机进行模拟试验,对比研究在不同的频率、波形、幅值和脉宽的激励信号作用下的响应和检测情况,得出了方波在传播过程中的衰减较锯齿波的小、信号传播中的衰减随频率上升而增大、脉宽过大时不利于故障判断、增大激励信号的幅值有利于提高故障检测的灵敏性等结论。

陕西“三北”防护林体系建设历史论析

陕西省是“三北”防护林体系建设工程重点省份。1949年以来,全省大力开展防风治沙、植树造林,控制水土流失取得明显成效,为“三北”防护林体系建设规划提供了实践支撑。文中通过档案等相关材料的梳理,总结1949年到中共十一届三中全会召开期间陕西防沙治沙、绿化造林对全国的影响及其在“三北”防护林体系建设工程的提出、规划和实施中的重要贡献,对于全面认识总结“三北”防护林体系建设的历史价值有重要意义。

帕米尔中部North Kyzkurgan冰川跃动变化遥感监测

跃动冰川作为一种特殊类型的冰川,蕴含着巨大的灾害风险,对其开展监测研究具有重要意义。本研究基于1973年以来的Landsat影像、ASTER立体像对和ITS_LIVE数据产品,监测分析了帕米尔中部North Kyzkurgan冰川在跃动前、跃动中、跃动后的面积、高程、流速变化,揭示了该冰川完整的跃动发生过程。结果表明:North Kyzkurgan冰川是一条典型的跃动冰川,在1973—2011年处于恢复阶;2011—2016年处于跃动阶;2016年之后重新进入恢复阶。North Kyzkurgan冰川所在地区气候寒冷,降雪量丰富,同时该冰川积累区面积比率超过0.8,冰川作用正差近1000 m,因此冰川补给物质充足。在积蓄区物质积累、不断增厚的情况下,冰川底部达到压力熔点,融水不断增多,在融水的润滑和顶托作用下,最终导致冰川发生跃动。因此,North Kyzkurgan冰川跃动的发生主要与热力学因素有关。

Numerical Study on the Bifurcation of the North Equatorial Current

A 1.5-layer reduced-gravity model forced by wind stress is used to study the bifurcations of the North Equatorial Current(NEC).The authors found that after removing the Ekman drift,the modelled circulations can serve well as a proxy of the SODA circulations on the σθ=25.0 kg m～-3 potential density surface based on available long-term reanalysis wind stress data.The modelled results show that the location of the western boundary bifurcation of the NEC depends on both zonal averaged and local zero wind stress curl latitude.The effects of the anomalous wind stress curl added in different areas are also investigated and it is found that they can change the strength of the Mindanao Eddy(ME),and then influence the interior pathway.

Derivation of Parametric Tropical Cyclone Models for Storm Surge Modeling

In this paper, the parametric tropical cyclone models for storm surge modeling are further developed. Instead of tangential wind speed via cyclostrophic balance and radial wind speed using a simple formulation of defection angle, the analyrical expressions of tangential and radial wind speed distribution are derived from the governing momentum equations based on the general symmetric pressure distribution of Holland and Fujita. The radius of the maximum wind is estimated by tropical cyclone wind structure which is characterized by the radial extent of special wind speed. The shape parameter in the pressure model is estimated by the data of several tropical cyclones that occurred in the East China Sea. Finally, the Fred cyclone （typhoon 199417） is calculated, and comparisons of the measured and calculated air pressures and wind speed are presented.

Development modes analysis of renewable energy power generation in North Africa

North African countries generally have strategic demands for energy transformation and sustainable development.Renewable energy development is important to achieve this goal.Considering three typical types of renewable energies—wind,photovoltaic(PV),and concentrating solar power(CSP)—an optimal planning model is established to minimize construction costs and power curtailment losses.The levelized cost of electricity is used as an index for assessing economic feasibility.In this study,wind and PV,wind/PV/CSP,and transnational interconnection modes are designed for Morocco,Egypt,and Tunisia.The installed capacities of renewable energy power generation are planned through the time sequence production simulation method for each country.The results show that renewable energy combined with power generation,including the CSP mode,can improve reliability of the power supply and reduce the power curtailment rate.The transnational interconnection mode can help realize mutual benefits of renewable energy power,while the apportionment of electricity prices and trading mechanisms are very important and are related to economic feasibility;thus,this mode is important for the future development of renewable energy in North Africa.