On the Variability of Charleston South Carolina Winds, Atmospheric Temperatures, Water Levels, Waves and Precipitation

Atmospheric winds, air temperatures, water levels, precipitation and oceanic waves in the Charleston South Carolina (SC) coastal zone are evaluated for their intrinsic, internal variability over temporal scales ranging from hours to multi-decades. The purpose of this study was to bring together a plethora of atmospheric and coastal ocean state variable data in a specific locale, to assess temporal variabilities and possible relationships between variables. The questions addressed relate to the concepts of weather and climate. Data comprise the basis of this study. The overall distributions of atmospheric and coastal oceanic state variable variability, including wind speed, direction and kinematic distributions and state variable amplitudes over a variety of time scales are assessed. Annual variability is shown to be highly variable from year to year, making arithmetic means mathematically tractable but physically meaningless. Employing empirical and statistical methodologies, data analyses indicate the same number of intrinsic, internal modes of temporal variability in atmospheric temperatures, coastal wind and coastal water level time series, ranging from hours to days to weeks to seasons, sub-seasons, annual, multi-year, decades, and centennial time scales. This finding demonstrates that the atmosphere and coastal ocean in a southeastern U.S. coastal city are characterized by a set of similar frequency and amplitude modulated phenomena. Kinematic hodograph descriptors of atmospheric winds reveal coherent rotating and rectilinear particle motions. A mathematical statistics-based wind to wave-to-wave algorithm is developed and applied to offshore marine buoy data to create an hour-by-hour forecast capability from 1 to 24 hours;with confidence levels put forward. This affects a different approach to the conventional deterministic model forecasting of waves.

Change of Annual Extreme Water Levels and Correlation with River Discharges in the Middle-lower Yangtze River: Characteristics and Possible Affecting Factors

As one of the fastest developing regions in China, the middle-lower Yangtze River （MLYR） is vulnerable to floods and droughts. With obtained time series of annual highest water level （HWL）, annual lowest water level （LWL） and the corresponding fiver discharges from three gauging stations in MLYR that covering the period 1987-2011, the current study evaluated the change character- istics of annual extreme water levels and the correlation with fiver discharges by using the methods of Vend test, Mann-Whitney-Pettitt （MWP） test and double mass analysis. Major result indicated a decreasing/increasing trend for annual HWL/LWL of all stations in MLYR during the study period. A change point in 1999 was identified for annual HWL at the Hankou and Datong stations. The year 2006 was found to be the critical year that the relationship between annual extreme water levels and fiver discharges changed in the MLYR. With contrast to annual LWL in MLYR, further investigation revealed that the change characteristics of annual HWL were highly consistent with regional precipitation in the Yangtze River Basin, while the linkage with Three Gorges Dam （TGD） operation is not strong. Our observation also pointed out that the effect of serious down cutting of the riverbed and the enlargement of the cross-section area during the initial period of TGD operation caused the downward trend of the relationship between annual LWL and river discharge. Whereas, the relatively raised river water level before the flood season due to TGD regulation since 2006 explained for the changing upward trend of the relationship between annual HWL and river discharge.

The effects of mean sea level rise and strengthened winds on extreme sea levels in the Baltic Sea

Mean sea level rise and climatological wind speed changes occur as part of the ongoing climate change and future projections of both variables are still highly uncertain. Here the Baltic Sea’s response in extreme sea levels to perturbations in mean sea level and wind speeds is investigated in a series of simulations with a newly developed storm surge model based on the nucleus for European modeling of the ocean(NEMO)-Nordic. A simple linear model with only two tunable parameters is found to capture the changes in the return levels extremely well. The response to mean sea level rise is linear and nearly spatially uniform, meaning that a mean sea level rise of 1 m increases the return levels by a equal amount everywhere. The response to wind speed perturbations is more complicated and return levels are found to increase more where they are already high. This behaviour is alarming as it suggests that already flooding prone regions like the Gulf of Finland will be disproportionally adversely affected in a future windier climate.

Characteristics Analysis and Risk Assessment of Extreme Water Levels Based on 60-Year Observation Data in Xiamen, China

Extreme water levels are related to astronomical tides and storm surges.Eleven typhoon systems,which have caused extreme water level rises,were selected based on 60-yr water level data from the Xiamen tide gauge station.In these 11 typhoon systems,the astronomical tide component accounts for 71%-95%of the total water level.The Gumbel distribution of extreme water level rise was estimated,and the impact of typhoon surges on water levels during the return period was analyzed.The ex-treme tide levels caused by typhoons Herb(1996)and Dujuan(2015)are much higher than those of other typhoons and correspond to the return period of 76 yr and 71 yr,respectively.The differences of sea levels in the presence and absence of these two typhoons in the 10-100 yr return period are 5.8-11.1 cm.For the 100-yr return period,the total risks within 10,25,50,and 100 yr increase by 94.3%,85.4%,72.9%,and 54.4%,respectively,if the Herb and Dujuan are not considered.Assuming that typhoon Herb(1996)occurred during the highest astronomical tide,it will produce a water level higher than that of the 1000-yr return period.Sea level rise has an important influence on the water level return period,and the contribution of nonlinear sea level rise in the next 100 yr is estimated to be 10.34%.

Case analysis of water exchange between the Bohai and Yellow Seas in response to high winds in winter

Based on the data from a special project titled China's Offshore Marine Integrated Investigation and Evaluation as well as Regional Ocean Modeling Systems(ROMS)diagnostic numerical model,we studied the influence of high wind processes on the circulation and water exchange between the Bohai and Yellow Seas(BYS)in winter.The results show that the vertical structure of the Yellow Sea Warm Current(YSWC)is relatively uniform under condition of high winds,showing obvious barotropic features.However,this flow is not a stable mean flow,showing strong paroxysmal and reciprocating characteristics.A comparison of the changes in sea level suggests that the intensity of the northwards upwind flow is consistent with the abnormal fluctuations in the sea level.It indicates that the upwind flow is closely related to the water exchange between the BYS.The impact of high wind processes on the water exchange between the BYS is enormous.It can make the flux through the Bohai Strait,as well as that through the mouth of each constituent bay(i.e.,Liaodong Bay,Bohai Bay,and Laizhou Bay)far greater than usual,resulting in a significant increase in the water exchange rate.The exchange capacity,which is about 8%of the total volume of the Bohai Sea,can be completed in a few days.Therefore,the water exchange of the Bohai Sea may be completed by only a few occasional high wind processes in winter.

Stochastic Model for Estimating Extreme Water Level in Port and Coastal Engineering Design

Extreme water level is an important consideration when designing coastal protection structures. However, frequency analysis recommended by standard codes only considers the annual maximum water level, whereas water levels should actually be regarded as a combination of astronomical tide and storm surge. The two impacting factors are both random variables, and this paper discusses their dependency structures and proposes a new joint probability method to determine extreme design water levels. The lognormal, Gumbel, Weibull, Pearson type 3, traditional maximum entropy, and modified maximum entropy distributions are applied to fit univariate data of astronomical tides and storm surges separately, and the bivariate normal, Gumbel-Hougaard, Frank and Clayton copulas are then utilized to construct their joint probability distributions. To ensure that the new design method is suitable for use with typhoon data, the annual occurrence frequency of typhoon processes is considered and corresponding bivariate compound probability distributions are proposed. Based on maximum water level data obtained from Hengmen hydrological station in the Pearl River Basin, China, these probability models are applied to obtain designs for extreme water levels using the largest sum of the astronomical tide and storm surge obtained under fixed joint return periods. These design values provide an improved approach for determining the necessary height of coastal and offshore structures.

东南风低空急流影响“21·7”郑州市极端暴雨分析

利用中国气象局上海台风研究所热带气旋(Tropical Cyclone,TC)最佳路径数据、美国环境预报中心(National Center of Environmental Prediction,NCEP)最终分析格点资料(Final Analysis,FNL)及常规观测数据等,分析了2021年7月郑州极端暴雨过程的特征机理。结果表明:(1)两个TC同时远距离输送大量水汽,东南风低空急流与强降水关系密切。当东南风急流北上到太原、邢台等站后郑州市暴雨减弱。郑州市6 h降水超过62.5 mm站点数目增减与850 hPa地转偏差数值变化趋势一致。(2) 20日白天郑州站极端降水发生前,从850 hPa经500 hPa至200 hPa风向从东南风顺转为西南风。200 hPa与850 hPa水平风的垂直切变(Vertical Wind Shear,VWS)从最大值开始减小、可降水量(Precipitable Water Vapor,PWV)明显加大、不稳定程度减小,这些都是极端暴雨发生的有利条件。极端暴雨具有明显的湿对流特点。(3)纬、经向风变率诊断表明,最有利于郑州市850 hPa东风维持的因子是地转偏差,最有利于南风加大的因子是动量平流。动量对流促使郑州市暴雨过程850 hPa南风减小,故动量上、下传递并非850 hPa南风加大原因。

2016—2022年太湖胥口湾水质变化及对水温、水位的响应

明确太湖胥口湾水质特征及对环境变化的响应有利于维系区域水资源安全。研究追踪2016—2022年胥口湾水质变化趋势,分析了水质指标对水温和水位的响应。结果显示,胥口湾水质环境总体稳定,且总氮(TN)、氨氮(NH_(3)-N)、总磷(TP)浓度和COD_(Mn)均呈下降趋势。但胥口湾水温年均值呈现快速上升趋势,上升幅度大于0.086℃·a^(-1),对该区域生态稳定性形成威胁。冗余分析显示,虽然水温和水位对胥口湾水质环境波动的贡献率低于5%,但水温变化显著影响了水质环境(P<0.01),而水位波动不能有效解释水质变化过程。尽管如此,TN、NH_(3)-N浓度及COD_(Mn)、pH值对高水温(>30℃)较为敏感,而高水位(>3.8 m)显著影响了NH_(3)-N、TN、TP和叶绿素a浓度。总体而言,胥口湾水环境总体稳定趋好,但受水位尤其是水温影响较大。研究结果可为极端天气下水质管理提供借鉴。

三峡库区卧沙溪滑坡变形机理及稳定性的研究

三峡库区是滑坡地质灾害频发地区,降雨条件下库区水位变化是导致边坡失稳的主要原因,但二者对滑坡的贡献及作用机理一直是三峡库区地质灾害研究重点.选取三峡库区卧沙溪滑坡为研究对象,利用非饱和土力学数值模拟进行研究,初步得出库水位下降是诱发卧沙溪滑坡失稳的主要因素,通过模拟库水位从175m下降到145m时,滑坡变形发生阶跃式的变化,导致滑体内部渗透力、位移场及水头压力发生变化,这些因素加快了滑坡体失去稳定性,产生滑坡.研究成果可为三峡库区地质灾害治理技术提供一定参考.

2022年“2.13”冀中大雪过程多源气象资料分析

利用常规观测资料、era5再分析资料、风廓线雷达产品、地基GPS/MET大气可降水量(precipitable water vapor,PWV)等,对2022年2月13日冀中大雪过程进行了详细分析。①降雪发生之前的36 h内PWV呈增长态势,0~12 h上升最快,12~36 h呈缓慢上升趋势。②降水量和PWV呈一定正相关关系,降雪期间PWV变化平稳,随着PWV出现连续下降,降水结束。③风廓线雷达的水平风向风速演变对降雪的预报有一定指示意义:3000 m突然出现20 m/s的西南低空急流,随着20 m/s的西南低空急流向下延伸至2500 m高度,降雪增强。④降雪之前,0.5 m/s及以上的正速度首先出现在1500 m以上,当2000 m以下突然出现1.0 m/s以上的正速度后,0~3 h内降雪发生。⑤1000 m以下垂直速度增加到1.5 m/s及以上时,降雪增强。⑥降雪期间C_(n)^(2)(大气折射率结构常数)一直稳定在-180~-165 dB,C_(n)^(2)值小于-180 dB时,最大探测高度降至3500 m以下,整层垂直速度小于0.5 m/s,预示降雪结束。

汛期水风光多能互补动态调度模型研究

为充分利用水电站水库汛期在预报无洪水或小洪水时的调节能力,将汛期运行水位动态控制域对应库容作为调节风光运行的可用库容,在提高水库调节能力的基础上给出了考虑入库洪水实时状态的汛期水电站水库动态消纳风光调度模式,以风光出力期望值加水电出力之和与负荷偏差最小为目标,结合风光出力不确定性建立了汛期水风光多能互补动态调度模型,并以福建省水口水电站为例进行模拟调度计算。结果表明:所提动态消纳风光调度模式能够在保证防洪安全的前提下充分合理利用水位动态控制域内的调节能力来调节风光出力,使失负荷时段数和发电量缺口期望值相较于传统调度模式分别降低约37%和32%,水电站水库平均发电水头提高约4.39%,不仅可提高系统出力可靠性,且能增加系统运行效益。研究成果可为汛期调节风光出力提供参考。

三峡水库消落带生境特征与植被恢复模式

[目的]三峡水库蓄水运行后消落带生境破碎斑块化加剧,极端生境胁迫严重损害植被的结构和功能。厘清三峡水库消落带生境状况,提出适宜性植被恢复对策,重建河流受损廊道综合生态功能,对构建区域生态安全格局和保障长江流域水资源安全具有重要意义。[方法]针对三峡水库消落带植被退化与生态功能受损的突出问题,系统解析了消落带生境特征及其对植被生长的影响,围绕水库河岸受损廊道生态修复重大需求,探讨面向消落带微生境构建与植被格局功能优化的三峡水库消落带植被恢复模式。[结果]三峡水库消落带生境状况受水库运行形成的独特水位节律、出露期植被生长季气候条件、土壤侵蚀与泥沙沉积过程、土壤环境等多生境因子协同影响,呈现高度空间异质性特征。水位变动形成的淹没时长、出露时令、淹水强度是影响植株繁衍、生长的首要因素;土壤侵蚀、泥沙掩埋、土壤水养条件等影响植被生长状况。[结论]三峡水库消落带植被恢复需综合考虑水位节律、立地条件与物种形态-功能性状,选育优质抗逆物种,注重土壤基质保育,突出植被格局的分区优化配置。重建消落带综合生态功能,为水库消落带生态治理提供理论支撑和科学依据。

极端干旱对鄱阳湖碟形湖水生植物群落的影响

水生植物是水生生态系统的重要组成部分,为底栖动物、鱼类和水鸟提供食物来源和栖息场所。近年来鄱阳湖水位变化剧烈,极端水文事件频发,对水生植物生长产生了不利影响。目前,关于极端干旱对鄱阳湖水生植物的影响报道较少。该研究于2022年7月和2023年7月对鄱阳湖典型碟形湖大湖池、沙湖及常湖池的水生植物群落进行调查,结果表明,2022和2023年鄱阳湖碟形湖平均水深分别为(160.27±50.70)、(58.00±21.46)cm,透明度分别为(49.10±14.41)、(47.25±10.91)cm。浮叶植物菱(Trapa spp.)优势度最大,沉水植物刺苦草(Vallisneria spinulosa)和轮叶黑藻(Hydrilla verticillata)优势度及生物量在2023年有所增加。湖区干旱导致水位降低,水体透明度发生变化,影响了植物群落的物种数,导致植物多样性增加。不同年份碟形湖水位和水体透明度的变化对水生植物多样性有显著影响,2 a间鄱阳湖碟形湖水生植物群落的物种组成差异显著,表现为2023年干旱后挺水和湿生植物比例增加。该研究通过对比分析2 a的监测数据,探讨了极端干旱对碟形湖水生植物的影响,研究结果可为鄱阳湖水生植物的恢复和越冬水鸟的食物资源补充管理提供科学依据。

风光消纳对梯级水库群运行水位的影响

水风光多能互补系统大多聚焦协同调度和提高新能源消纳研究,却忽略了风光能源消纳对水库水位的潜在影响。构建了考虑短期弃电特征的水风光互补系统中长期优化调度模型。首先,根据实际水风光出力模拟可能的弃电情景,拟合弃电损失函数,将其嵌套在中长期优化调度模型中;其次,模拟接入风光前后的水库调度运行过程;最后,分析风光消纳对梯级水库群年际、年内、月运行水位的影响。以黄河上游龙羊峡至刘家峡梯级水电站水风光互补系统为实例,研究表明:①接入风光后,梯级水库群的年均出力降低约0.5%,可促进风光消纳,保证系统总出力更大,可提高风光上网出力和系统总出力约2.2%;②风光消纳导致梯级水库群的年际和月水位波动增加,龙羊峡和刘家峡水库的年末消落水位和年均水位的波动范围分别增加2.5%、101.6%、0.8%和78.9%,龙羊峡的月水位波动变幅为0,刘家峡月水位下限降低14.7%;③在丰水年,接入风光后梯级水库水位显著下降;平水年,龙羊峡水库水位稍有降低,刘家峡水库的水位表现为汛前春季水位降低,汛后秋季水位升高;枯水年,风光消纳对水库水位几乎没有影响。这些研究结果对于更好地理解风光能源与水库运行之间的复杂关系以及优化水风光互补系统的运行策略具有重要的实际意义。

长江口徐六泾水文站极值水位研究

在气候变化背景下,极端天气和水位事件频发。为了分析长江口极端潮位的长周期特征,研究基于极值理论相关方法,采用近33 a实测资料对长江口极值潮位趋势性和重现期进行分析,结果表明:长江口徐六泾站年极值水位呈轻微下降趋势,直接原因是大通流量减少导致当地年均海面的下降;区分组模型结果显示,台风“温妮”期间长江口造成的风暴潮位为100 a一遇,而POT模型计算结果仅为60 a一遇,100 a一遇重现期潮位约7.0 m;潮位重现期的计算本质是一种用频率代替概率、从样本推求整体的过程,具有一定不确定性。其意义在于以可获取的数据为基础,计算事件发生的风险率,旨在为工程设计或风险管理提供依据。

渤、黄海天文潮—风暴潮相互作用及其对极值水位的贡献

基于Delft3D模型建立了中国渤、黄海风暴潮数值模型,选取1979—2020年影响该海域的93场风暴过程(包括台风、寒潮和温带气旋),模拟了所产生的风暴增水和风暴潮总水位。采用泊松—皮尔逊复合极值分布理论,推算了渤、黄海对应不同重现期的极值水位;通过数值试验,对天文潮—风暴潮非线性相互作用对极值水位的贡献进行了量化分析。研究结果表明,渤海的莱州湾、渤海湾,以及黄海的江华湾、西朝鲜湾风暴增水最大,其中江华湾北侧和渤海湾西南侧的百年一遇风暴增水可达4 m;天文潮—风暴潮非线性相互作用在潮差较大、水深较浅的河口、湾顶区域更为显著,与耦合模型结果相比,非线性作用使极值水位值偏小,天文潮、风暴潮增水的线性叠加可显著高估极值水位,高估的幅值可达0.5~0.8 m。考虑重现期极值水位是海岸灾害防护工程的关键设计参数之一,对海岸构筑物的安全和建造成本影响极大,应重视天文潮—风暴潮非线性相互作用对重现期水位的影响。

甬江流域鄞州平原区极端洪水对暴雨的响应特征

为深刻揭示变化环境下甬江流域鄞州平原区雨洪关系特征,以姜山水文站为例,基于1962—2021年逐日降水和水位观测资料,利用分位数扰动法和极端降雨水位时变相关模型,从扰动过程和时变关系两个方面,探讨了水位对极端暴雨的响应特征演变趋势。结果表明:近60年姜山水文站年最大1、3 d降水量和年最大水位均呈显著上升趋势,变化倾向率分别为8.39 mm/10 a、12.66 mm/10 a和0.67 m/10 a;年最大1、3 d降水量和最大水位均呈现相似的阶段性扰动特征,即1960—1984年以负扰动为主,1985—2012年扰动强度较为平稳,2013—2021年为显著扰动;在选用的12个模型中,Time-varing Normal、Time-varing Rotated Gumbel、Timevaring Symmetrized Joe-Clayton等3个动态时变响应模型能更好地拟合极端洪水对暴雨的响应。总体上,年最大水位对年最大3 d降水量的响应以1990s—2000s为高值期,呈现先升后降的阶段性特征。研究结果可以加深城镇化对雨洪关系影响机制的认知,也可供区域洪涝灾害预警和预测参考。

1970—2020年黄土高原水蚀风蚀交错区极端降水时空变化研究及驱动因素分析

黄土高原水蚀风蚀交错区作为中国北方典型的生态脆弱区,因其独特地形和气候条件,极端降雨事件对其环境和生态系统的影响更加突出。选取水蚀风蚀交错区28个气象站点,结合RClimDex模型计算11个极端降水指数,采用线性相关分析法、Mann-Kendall趋势检验法和小波交叉法,分析了1970—2020年黄土高原水蚀风蚀交错区极端降水事件时空分布特征,探讨了极端降水事件的驱动因素。结果表明:(1)1970—2020年水蚀风蚀交错区持续干燥日数(CDD)呈下降趋势,其余10个指数呈上升趋势,反映出近50a研究区极端降水事件的频率、量级和强度不断增加。交错区年降水量增加和极端降水事件增加具有密切关系,且极端降水事件增加主要是由中雨日数(R10)和大雨日数(R20)引起。(2)1970—2020年极端降水事件在全区整体为增加趋势,交错区中部和西南部极端降水事件显著发生,陕西段极端降水量和强度呈显著增加趋势且极端化程度更显著。(3)湿日总降水量(PRCPTOT)、暴雨日数(R25)、5d最大降水量(R5d)3个极端降水指数,与影响因子厄尔尼诺-南方涛动(ENSO)、东亚夏季风(EASM)和太阳黑子(SN)具有不同的功率,与SN的交叉小波变换功率最大,说明影响因子中SN和极端降水指数的相关性最高,SN对极端降水事件的影响最大。

长江安庆段长江江豚分布特征及其影响因子探究

研究于2021年秋季至2023年夏季在长江安庆段(安庆市程营村-凤凰码头)开展了2个周年共8次目视考察,从种群数量、集群规模、迁移规律、栖息地偏好四个方面探讨了该水域长江江豚(Neophocaena asiaeorientalis asiaeorientalis)的分布特征及影响因子。研究期间共观测到长江江豚555群次、1000头次,最大单次评估结果为192头;其中2023年观测到长江江豚336群次、603头次,较2022年分别上升53.4%和51.9%。研究期间长江江豚最大集群规模为8头,平均集群规模为1.8头/群。考察发现长江安庆段长江江豚总体呈连续分布,但存在明显的热点区域,其中张家州北汊、上三号洲、下三号洲洲尾及清洁洲洲头水域为长江江豚的重要栖息地,四个栖息地内观测头次分别占总头次的19.3%、4.9%、12.6%和10.8%。禁捕后长江江豚在河口汇流区活跃的月份增加并有从八里江安徽段向下游扩散分布的趋势,但码头、崩岸区对其栖息地范围的拓展仍存在一定影响,华阳河口以下江段仍只有清洁洲洲头水域为长江江豚的重要栖息地。因此研究认为在十年禁渔及鄱阳湖极端枯水频发的背景下,长江安庆段的长江江豚数量有明显上升趋势,同时长江江豚对各重要栖息地斑块之间迁移通道的利用情况逐渐好转,分布更具连续性。研究建议,应在长江江豚可能的聚集觅食区及迁移通道保持自然岸线占比,加大岸线整治力度,加强人类活动管控;根据极枯水位下鄱阳湖长江江豚迁移入江的时序特征,制定湖口-华阳河口水域的应急管理预案。

风光电解水制氢平准化成本优化空间分析

氢能是中国绿色低碳能源体系的组成部分和“双碳”目标实现的关键载体,其未来可持续发展是以电解水生产的“绿氢”为方向,但目前针对可再生能源制“绿氢”的最新平准化成本以及成本优化空间较少受关注。对此,基于我国制氢行业最新数据计算出“绿氢”最新平准化成本,并对系统发电侧和制氢侧成本优化空间进行分析,最后开展敏感性分析。结果表明:我国“绿氢”最新平准化价格为20元/kg,已接近目前传统化石原料生产的“灰氢”成本,综合发电侧和制氢侧成本优化空间,至2030年可使氢气平准化成本下降48%左右,达到10.4元/kg;电价敏感性方面,风光电价每降低0.02元/kWh,氢气平准化成本降低约1.2元/kg。