Analytic Study of Sea-Land Breezes

An analytic study of the structure of sea-land breezes is presented, with special attention paid to the dependence on the model parameters. In this linearized model, the wind speed of the sea-land breezes is directly proportional to the difference of sea and land heating rates. For the same differential heating, the sea-land breeze is more prominent if the stratification is weakly stable, or if the frictional force is small. The horizontal penetration from the coast is also investigated, and found to be asymmetric between the land and the sea. The above results are in agreement with observation.

STATISTICAL CHARACTERISTICS AND NUMERICAL SIMULATION OF SEA-LAND BREEZES IN HAINAN ISLAND

The sea-land breeze circulation(SLBC) occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorological stations of Hainan Island, the frequency of sea-land breeze(SLB) is studied to depict the diurnal and seasonal variations. The statistics indicated that there is a monthly average of 12.2 SLB days and an occurrence frequency of about 40%, with the maximum frequency(49%) in summer and the minimum frequency(29%) in autumn. SLB frequencies(41%) are comparable in winter and spring. A higher frequency of SLB is present in the southern and central mountains due to the enhancement effect of the mountain-valley breeze. Due to the synoptic wind the number of SLB days in the northern hilly area is less than in other areas. Moreover, the WRF model, adopted to simulate the SLBC over the island for all seasons, performs reasonably well reproducing the phenomenon, evolution and mechanism of SLBC. Chiefly affected by the difference of temperature between sea and land, the SLBC varies in coverage and intensity with the seasons and reaches the greatest intensity in summer. The typical depth is about 2.5 km for sea breeze circulation and about 1.5 km for land breeze circulation. A strong convergence zone with severe ascending motion appears on the line parallel to the major axis of the island, penetrating 60 to 100 km inland. This type of weak sea breeze convergence zone in winter is north-south oriented. The features of SLBC in spring are similar both to that in summer with southerly wind and to that in winter with easterly wind. The coverage and intensity of SLBC in autumn is the weakest and confined to the southwest edge of the central mountainous area. The land breeze is inherently very weak and easily affected by the topography and weather. The coverage and intensity of the land breeze convergence line is significantly less than those of the sea breeze. The orographic forcing of the central mountain exhibits significant impacts on low-level airflow. A windward land breeze front usually occurs along the coastline between the wee hours and the morning in summer, with an arc-shaped convergence zone about 10 to 30 km off shore. In winter the arc-shaped convergence zone is weak and appears only in the southeast coastal area. Landing on the flat regions of northern to western parts of the island and going inland from there, the sea breeze front at the leeward side meets with that at the windward side in the centre of the island when sea breeze fully develops, causing an intense convergence zone throughout the whole island. Consistent with prevailing winds in direction, the windward sea breeze and leeward land breeze develop quickly but are not distinguishable from background winds.

Evolution Mechanism of a Severe Squall Line Triggered by the Coupling of a Sea Breeze Front and a Gust Front

In the present study, a severe squall line(SL) was analyzed by using intensive observational surface data and radar monitoring products. In this process, mesoscale convergence lines, such as the sea breeze front(SBF), gust front and dry line, served as the main triggering and strengthening factors. The transition from convection triggering to the formation of the initial shape was mainly affected by the convergence line of the SBF, which combined with thermal convection to form the main parts of the SL. In the later stage, the convergence line of the gust front merged with other convergence lines to form a series of strong convective cells. The SBF had good indicative significance in terms of severe convective weather warnings. The suitable conditions of heat, water vapor and vertical wind shear on the Shandong Peninsula were beneficial to the maintenance of the SL. Before SL occurrence, tropopause folding strengthened, which consequently enhanced the baroclinic property in the middle and upper troposphere. The high sensible heat flux at the surface easily produced a positive potential vorticity anomaly in the low layer, resulting in convective instability, which was conducive to the maintenance of these processes. In the system, when precipitation particles passed through the unsaturated air layer, they underwent strong evaporation, melting or sublimation, and the cooling effect formed negative buoyancy, which accelerated the sinking of the air and promoted the sustained development of the surface gale. Together with the development of lowlevel mesocyclones, the air pressure decreased rapidly, which was conducive to gale initiation.

A Case Modeling of Sea-Land Breeze in Macao and Its Neighborhood

PSU / NCAR MM5 was utilized to simulate the sea-land breeze circulation in Macao and the three-dimensional flow around the Pearl River estuary. Four two-way nested grids having resolution of 1, 3, 9, and 27 km were included in the simulation. It was initialized with conventional observational data, and a 30 h simulation and analysis of one sea-land breeze case were performed. It was shown, that the model with a finer resolution (1 km) captures the sea breeze and land breeze in Macao with reasonable skill. The sea breeze front and the thermal internal boundary layer (TIBL) were also obviously revealed. However, the coarser horizontal resolution (3 km) could capture the sea breeze but not the land breeze.

The Structure and Evolution of Sea Breezes During the Qingdao Olympics Sailing Test Event in 2006

Using data from automatic surface weather stations, buoys, lidar and Doppler, the diurnal variation and the three-dimensional structure of the sea breezes near the sailing sites of the Good Luck Beijing- 2006 Qingdao International Regatta from 18 to 31 August 2006 are analyzed. Results show that excluding rainy days and days affected by typhoon, the sea breezes occur nearly every day during this period. When Qingdao is located at the edge of the subtropical high at 500 hPa, the sea breeze is usually stronger, around 3-4 m s^-1. It starts at around 1100 to 1300 LST and lasts about 6 hours. The direction of the sea breeze tends to be southeasterly. When Qingdao is under the control of the subtropical high, the sea breeze is usually weaker, less than 2.5 m s^-1 throughout the day, and begins later, between 1300 and 1500 LST. In this case, the direction of the sea breeze is variable from easterly to southeasterly. Most sea breezes in Qingdao are very shallow, up to 300 meters deep. Strong sea breezes can reach 1.5 km in depth and can push as far as 100 km inland. If the Huanghai sea breeze moves inland and meets the sea breeze of the Jiaozhou Bay in the western part of Qingdao, the sea breeze will strengthen and form three boundaries due to the interaction of the two sea breezes.

Characteristics of Lake Breezes and Their Impacts on Energy and Carbon Fluxes in Mountainous Areas

In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin,southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux(Hs) and carbon dioxide flux(F_(CO_2)) and increases the latent heat flux(LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases F_(CO_2). For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases suppress carbon dioxide exchange.

The research of sea-land breeze (SLB) on the west coast of Bohai Bay based on field observation

Four automatic meteorological stations were set up in a line from beach to inland perpendicular to the west coast of Bohai Bay. Wind direction and velocity at altitudes of 2 m, 4 m and 12 m were surveyed with 10 minute intervals. On ＂Sea-Land Breeze＂ （SLB） days, the transition from sea breeze to land breeze was very evident in the study area. Direction of sea breeze was basically perpendicular to the coast and mainly from the ENE and E. Duration of sea breeze varied by the stations＇ distance to the coastline, and the near-coast wind velocity was larger than that of the inland and decreases as it reaches inland. There was increased development of SLB on sunny days than on overcast days. The term ＂Climatic Coastal Zone＂ can be defined for the area influenced by SLB, which reaches more than 74 km inland on a typical SLB day but less than 10 km on a non-typical SLB day.

NUMERICAL EXPERIMENT ON THE EFFECT OF URBANIZATION UPON SUMMER LAND-SEA BREEZES IN THE COASTLAND OF GUANGXI

The 2003-006 observations were utilized to analyze the surface characteristics of summer land-sea breezes along the coastland of Guangxi and the Weather Research and Forecast model was applied to simulate the breeze structure on August 1-2, 2006. Results show that 1） the intensity and distributions of the breezes reproduced from improved urban underlying surface were close to observations. In the daytime the coastwise urban band was a convergent belt of sea breeze, corresponding to the centers of torrential rains; in the nighttime hours the surface of the Gulf of Tonkin （the Vietnamese name） or the Northern Bay （the Chinese name） acted as a convergent zone of land breezes, likely to produce convective cloud cluster; 2） the experiment on urbanization showed the heat island effect enhancing （weakening） the sea （land） breeze development. Furthermore, the heat island effect mitigated the atmospheric cooling via radiation over the cities in the night, weakening sinking motion correspondingly, thereby suppressing the dominant factor responsible for the steady development of temperature inversion. As a result, the inversion vigor was reduced greatly, but nevertheless no strong effect of the decreased subsidence was found upon the inversion height.

Whether human-induced activities could change the gradient pattern of coastal land use along the sea-land direction:a case study in Manila Bay,Philippines

Increasing intense human activities have largely changed the coastal landscape and caused many environmental issues.However,whether human-induced activities could change the coastal land use gradient pattern,an important coastal zonal characteristic along the sea-land direction,remains unclear.Manila Bay was selected as the study area in this work.According to the distance of the land use and land cover(LULC)to the coastline,we clustered the typical coastal land use sequence patterns(CLUSPs)along the sea-land direction between 1988 and 2016 in Manila Bay and found the following.(1)Four typical CLUSPs,including the natural CLUSP dominated by forest land and grassland,the agricultural CLUSP dominated by dry farm and paddy field,the urbanised CLUSP dominated by construction land and the fishery CLUSP dominated by fishing farm,were mined in 1988.Three typical CLUSPs(a natural CLUSP,an intermediate CLUSP between the agricultural and urbanised CLUSPs,and a fishery CLUSP)were mined in 2016.(2)Affected by the dominant LULC,these typical CLUSPs showed a regular spatial pattern along the sea-land direction.For example,the typical natural CLUSP showed a landward pattern due to the long distance between the forest land and grassland and the coastline.(3)However,influenced by urban and aquaculture expansion,the land intensification of the CLUSP exhibited an obvious increase and caused the decrease of the CLUSP diversity from 1988 to 2016.The increase in the area of LULC coverage showed no obvious correlation with its distance from the coastline(DFC),but the net increase rate of LULC coverage had a significant negative correlation with the DFC.Therefore,human-induced activities have a large impact on the gradient pattern of coastal land use along the sea-land direction.

Sea-Land Segmentation of Remote Sensing Images Based on SDW-UNet

Image segmentation of sea-land remote sensing images is of great importance for downstream applications including shoreline extraction,the monitoring of near-shore marine environment,and near-shore target recognition.To mitigate large number of parameters and improve the segmentation accuracy,we propose a new Squeeze-Depth-Wise UNet(SDW-UNet)deep learning model for sea-land remote sensing image segmentation.The proposed SDW-UNet model leverages the squeeze-excitation and depth-wise separable convolution to construct new convolution modules,which enhance the model capacity in combining multiple channels and reduces the model parameters.We further explore the effect of position-encoded information in NLP(Natural Language Processing)domain on sea-land segmentation task.We have conducted extensive experiments to compare the proposed network with the mainstream segmentation network in terms of accuracy,the number of parameters and the time cost for prediction.The test results on remote sensing data sets of Guam,Okinawa,Taiwan China,San Diego,and Diego Garcia demonstrate the effectiveness of SDW-UNet in recognizing different types of sea-land areas with a smaller number of parameters,reduces prediction time cost and improves performance over other mainstream segmentation models.We also show that the position encoding can further improve the accuracy of model segmentation.

Research on Breeze Vibration Law and Modal Identification Method of Conductor Considering Anti-Vibration Hammer Damage

In the harsh environment,the structural health of the anti-vibration hammer,which suffers from the coupled effects of corrosion and fatigue damage,is significantly reduced.As part of the conductor structure,the anti-vibration hammer is rigidly attached to the conductor,effectively suppressing conductor vibration.The conductor’s breeze vibration law and natural modal frequency are altered damage to the anti-vibration hammer structure.Through built a vibration experiment platform to simulate multiple faults such as anti-vibration hammer head drop off and position slippage,which to obtained the vibration acceleration signal of the conductor.The acceleration vibration signal is processed and analyzed in the time and frequency domains.The results are used to derive the breeze vibration law of the conductor under multiple faults and propose an anti-vibration hammer damage online monitoring technology.The results show that the vibration acceleration value and vibration intensity of the conductor are significantly increased after the anti-vibration hammer damage.The natural frequency increases for each order,with an absolute change ranging from 0.15 to 6.49 Hz.The anti-vibration hammer slipped due to a loose connection,the 1st natural frequency increases from 8.18 to 16.62 Hz.Therefore,in engineering applications,there can be no contact to determine the anti-vibration hammer damage situation by monitoring the modal natural frequency of the conductor.This is even a tiny damage that cannot be seen.This method will prevent the further expansion of the damage that can cause accidents.

中国典型复杂地形风能资源特性及其形成机制

为提高对复杂地形风资源特性及其形成机制的认识,改进复杂地形风场数值模拟方法,分别选取代表极大起伏山地与宽谷地形的藏南谷地、代表极大起伏山地与深谷地形的横断山区以及代表中、小起伏丘陵山地的山西高原开展风资源特性观测实验,分析不同典型复杂地形条件下天气背景风场、局地大气环流、地形动力强迫、地表摩擦与热力作用对风资源特性形成的贡献,结果表明:山西高原局地大气环流的作用较小;藏南谷地和横断山区的山谷风环流对其风能资源特性的形成起主要作用,尤其是横断山区还存在多尺度的局地大气环流,传统的风电场风资源CFD数值模拟不足以描述如此复杂的风场。因此,在局地大气环流作用明显的复杂地形地区,需要采用中尺度与CFD结合的风电场选址风资源数值模拟方法。

基于概率密度演化的大跨越导线铝部风振疲劳可靠度分析

为了掌握微风作用下大跨越架空输电导线铝股疲劳特性及其可靠度,提出了基于概率密度演化的大跨越输电导线铝部疲劳可靠度计算方法.首先建立了大跨越塔线体系有限元模型,研究了微风激振下导线悬挂点处振动位移时程,然后构建了导线节段有限元实体模型,以微风激振作用下导线位移时程为激励,研究了大跨越导线内外层铝股风振疲劳应力时程响应,最后采用概率密度演化方法,考虑线路风速风向概率分布,分析了大跨越导线疲劳可靠度,并与Miner线性累积损伤结果进行比较.结果表明:微风风速越大,大跨越导线振幅越大;微风作用下大跨越导线的外层铝股应力大于内层铝股,外层的钢股应力亦大于内层;大跨越导线运行年限越大,导线内外层铝股可靠度越小,但内层铝股可靠度大于外层铝股可靠度;基于Miner原理计算的铝股疲劳可靠度偏大,建议开展大跨越输电导线疲劳设计时考虑分层特性.

海南岛土地覆盖变化对海风锋结构演变影响的数值模拟

本文利用WRF-Noah陆气耦合中尺度模式,针对海南岛一次典型的海风锋事件进行了高分辨率的数值模拟,研究了海南岛土地覆盖(下垫面)变化对海风锋结构演变的影响及其机制。结果表明,海南岛土地覆盖变化对海风锋的作用是通过多种地表和植被属性的综合影响决定的。森林化试验中动力和热力作用分别抑制和促进海风锋的发展,对海风锋的影响是两者共同作用的结果;反照率的减小引起净辐射的增大,从而使感热通量小幅增加,使低层大气增温而增加海陆温度梯度,这在一定程度上增强了海风驱动力,但地表粗糙度的增大减弱了海风风速,进一步减弱了海风锋传播距离和上升速度。然而,由于海南岛森林覆盖面积较大,导致森林化试验与控制试验中海风锋的整体差异较小。相比之下,荒漠化试验中热力和动力作用均有利于海风锋的发展;反照率的增大和叶面积指数的降低,改变了地表能量分配,造成潜热通量显著减小,感热通量先减少后增大,对低层大气的增温效应非常明显,从而加大了海陆温度梯度。另一方面,地表粗糙度显著减小,下垫面对海风的阻挡作用减弱,海风风速增大。因此,荒漠化试验海风锋传播距离、上升速度以及海风厚度都显著增大。

弱天气背景下天津三次局地突发暴雨中尺度特征及触发机制

利用ERA5再分析(0.25°×0.25°)、加密自动气象站、多普勒天气雷达和变分多普勒天气雷达分析系统等高时空分辨率资料,对比分析了2018年7月22日、2019年7月18日、2021年8月23日天津中心城区三次局地突发性暴雨过程的中尺度特征及其触发机制。结果表明:三次局地突发性强降雨均无明显天气尺度系统主导,但环境大气具备较高的对流不稳定能量和较小的对流抑制能量,抬升凝结高度仅0.2~0.4 km,且低层均存在一定的湿层。局地突发性暴雨的发生与城市热岛及海陆下垫面特征差异造成的中小尺度系统有关,暴雨发生前天津中心城区与沿海地区之间的温差和气压差增大,中心城区附近温压场具有明显的非均匀分布特性,中尺度暖低压及其东侧的高温度梯度为局地对流发生提供了有利的中尺度环境条件。此外,暴雨发生前沿海地区均出现了明显的海风加强,城市热岛暖低压辐合与海风风速辐合共同作用使得中尺度辐合强度明显加强,是局地突发性暴雨发生的主要原因,初生的γ中尺度对流单体均位于地面强辐合中心边缘上空。

海南岛沿海城镇化对海风锋推进影响的数值模拟

本文利用中尺度模式WRF-ARW(Weather Research and Forecasting Model-Advanced Research WRF)(Version 4.0)对海南岛不同天气条件下的典型海风锋个例进行了高分辨率数值模拟,通过设计局地城镇化的敏感性试验,重点分析了海南岛沿海城镇化对海风锋推进的影响及其可能机制。研究结果表明:海南岛沿海城镇化造成的海风锋结构差异是热力作用和动力作用共同影响的结果;城镇下垫面的摩擦效应与城市热岛的增强阻碍海风向内陆推进,减弱了海风锋途经地区的降温增湿效应,造成海风锋位置相对滞后;而城镇化所引起的高海陆热力差异增强了海风风速及海风辐合,同时导致海风锋前的垂直上升气流和海风环流厚度也明显增强。海风锋发展不同时期,城镇化对海风锋的推进影响有所不同。海风锋发展初期,海陆热力差异引起的推动作用与摩擦效应的阻碍作用相抵消,导致海风锋的推进无明显影响;海风锋发展强盛阶段,城镇化条件下内陆城市与非城市之间的热力差异有所增强,阻碍了海风锋向内陆推进,导致海风锋内陆渗透距离减小。不同天气条件下城市化对海风锋推进的影响有所不同,相比于晴空天气,多云天气下城市与非城市的热力差异稍强,加强了城市热岛效应对海风推进的阻碍作用,导致海风锋滞后距离稍远。此外,当土地利用类型更换为城镇后,净辐射与陆气间交换能量减少,导致其潜热通量显著减小,感热通量值变大,从而升高了下垫面温度,增强了海风的垂直上升运动,进而造成边界层高度的升高。

Influence of sea-land breeze on the formation and dissipation of severe dense fog and its burst reinforcement in the Yellow Sea coastal area,China

Based on the global reanalysis data of the National Centers for Environmental Prediction(NCEP)/National Center for Atmospheric Research,the surface meteorological observation data,sounding data and satellite observation data,this paper comprehensively analyzes the evolution process and formation mechanism of a persistent severe dense fog process occurred on February 15–17,2015 in Yancheng,eastern China.Through the numerical simulation experiment of Weather Research and Forecast(WRF)model,we further analyze the impact of sea-land breeze on the formation and burst reinforcement of fog.Results show that the precipitation caused by the southwesterly airflow in front of the upper-level trough and the low-pressure inverted trough are conducive to the formation of early rain fog,while the nighttime clear radiance under the control of surface cold high and the infiltration of weak cold advection are conducive to the formation and development of later radiation-advection fog.The WRF model simulates the fog evolution process,which is basically consistent with the actual fog area,and the simulation results are credible to a certain extent.The simulation results show that the establishment of sea breeze has an advection cooling effect on the near surface layer,which is conducive to the formation and development of the inversion layer on the near surface,providing stable stratification conditions for the formation and burst reinforcement of fog.On one hand,the strengthening of sea breeze circulation can continuously transport water vapor to the study area.On the other,the occurrence of ultra-low level jet is favorable for the accumulation of low-level water vapor.At the same time,the inversion intensity further strengthens,which is in favor of the burst reinforcement and long-term maintenance of fog.

大型浅水湖泊高时空分辨率风场特征数值模拟研究:以巢湖为例

【目的】大型浅水湖泊的风场是影响湖泊流场、水体富营养化和藻华运移聚集规律的关键因素之一,仅依托气象站点的观测数据难以有效捕捉湖面风场在空间和时间上的快速变化。为精细刻画湖泊高频变化风场,辨识其时空变化特征,【方法】以巢湖为研究对象,综合利用气象观测数据、全球再分析数据集和地理静态数据,通过中尺度天气预报模式和地理空间分析技术,模拟分析巢湖地区2019年高时空分辨率的风场变化过程。【结果】结果显示:巢湖区域风速由东向西、由南向北、由湖面向陆面逐渐减弱;湖面主导风向为东风和偏东风,主导风速为二级至四级,湖面平均风速在11月最大,12月次之,5月最小,不同季节湖面平均风速由大到小依次为冬季、秋季、夏季和春季。【结论】结果表明:巢湖在白天(夜晚)出现冷(暖)湖效应,其风场在早上6时和夜晚23时出现陆风和湖风转换;西半湖受湖陆风和城市热岛影响显著,在夏季会出现明显的环湖湖风锋,其湖风锋穿透内陆距离约4.7~9 km;东半湖受山谷风影响显著,在东南部山脉以东湖区易形成低风速区,在湖口附近受狭管效应易形成高风速区。通过研究成果可进一步认知巢湖区域风场特征,为巢湖水生态环境治理提供技术支撑。

生物质燃料用于铁矿烧结的研究进展

生物质燃料由于来源广泛、储量巨大且具有高发热值、高纯度、低成本的优势而具有良好的应用前景,其应用于烧结生产也是钢铁行业低碳绿色高质量发展的重要途径之一。本文从原料制粒、烧结过程、烟气减排三个方面对生物质燃料在铁矿烧结工艺中的应用进行系统性的归纳与分析。在原料制粒方面,生物质燃料相较于焦粉和无烟煤,在烧结生产时需要配入更大的水分,根据生物质燃料的种类该水分配比可能需要增加1%~5%。在烧结过程方面,受限于燃烧特性,生物质燃料替代焦粉的比例不宜过高,一般为10%~40%,进一步提高该配比则会出现烧结矿成品率和转鼓指数、烧结机利用系数的显著降低。在烟气减排方面,生物质燃料在降低烧结烟气中CO、NO_(x)、SO_(x)、粉尘和二噁英等有害污染物排放量方面作用显著。对于大规模工业化应用,仍需继续加深理论与试验探索,进一步提高生物质燃料的可获得性,统筹生物质燃料回收加工处理的配套产业,并加大包括投资鼓励等政策支持。

渤海湾海陆风环流及臭氧特征分析

利用2023年夏季在乐亭县开展的观测实验数据和相关气象数据及环境数据,分析渤海湾地区海陆风环流及其对臭氧污染的影响。结果表明,海陆风环流可以影响臭氧在海陆间输送,可能导致渤海湾上空及沿海地区臭氧污染。HYSPLIT后向轨迹模拟解析共有5条主要气团轨迹影响到实验观测地区,其中有2条偏南方向气团通过短距离输送进入实验地区,对该区域的臭氧污染贡献率高达65%。