Diurnal Variation of MCSs over Asia and the Western Pacific Region

Mesoscale convective systems (MCSs) are severe disaster-producing weather systems. Radar data and infrared satellite image are useful tools in MCS surveillance. The previous method of MCS census is to look through the printed infrared imagery manually. This method is not only subjective and inaccurate, but also inefficient. Different from previous studies, a new automatic MCS identification (AMI) method, which overcomes the above disadvantages, is used in the present study. The AMI method takes three steps: searching potential MCS profiles, tracking the MCS, and assessing the MCS, so as to capture MCSs from infrared satellite images. Finally, 47468 MCSs are identified over Asia and the western Pacific region during the warm seasons (May-October) from 1995 to 2008. From this database, the geographical distribution and diurnal variation of MCSs are analyzed. The results show that different types of MCSs have similar geographical distributions. Latitude is the main control factor for MCS distribution. MCSs are most frequent over the central Tibetan Plateau; meanwhile, this area also has the highest hail frequency according to previous studies. Further, it is found that the diurnal variation of MCSs has little to do with MCSs’ size or shape; MCSs in different areas have their own particular diurnal variation patterns. Based on the diurnal variation characteristics, MCSs are classified into four categories: the whole-day occurring MCSs in low latitude, the whole-day occurring MCSs in high latitude, the nocturnal MCSs, and the postmeridian MCSs. MCSs over most places of mainland China are postmeridian; but MCSs over the Sichuan basin and its vicinity are nocturnal. This conclusion is coincidental with the hail climatology of China.     

The Characteristics of Mesoscale Convective Systems (MCSs) over East Asia in Warm Seasons

Mesoscale convective system (MCS) cloud clusters,defined using an objective recognition analysis based on hourly geostationary infrared satellite data over East Asia during the warm seasons of 1996-2008 (except 2004),were investigated in this study.The geographical pattern of MCS distribution over East Asia shows several high-frequency centers at low latitudes,including the Indo-China peninsula,the Bay of Bengal,the Andaman Sea,the Brahmaputra river delta,the south China coastal region,and the Philippine Islands.There are several middle-frequency centers in the middle latitudes,e.g.,the central-east of the Tibet Plateau,the Plateau of west Sichuan,Mount Wuyi,and the Sayan Mountains in Russia;whereas in Lake Baikal,the Tarim Basin,the Taklimakan Desert,the Sea of Japan,and the Sea of Okhotsk,rare MCS distributions are observed.MCSs are most intensely active in summer,with the highest monthly frequency in July,which is partly associated with the breaking out and prevailing of the summer monsoon in East Asia.An obvious diurnal cycle feature is also found in MCS activities,which shows that MCSs are triggered in the afternoon,mature in the evening,and dissipate at night.MCS patterns over East Asia can be characterized as small,short-lived,or elongated,which move slowly and usually lead to heavy rains or floods.     

基于静止卫星红外云图的MCS普查研究进展及标准修订

基于静止卫星红外云图的MCS普查标准不统一不利于各种MCS普查结果的对比分析, 该文在总结MCS普查研究进展的基础上, 依据Orlanski尺度分类标准对MβCS普查的最小尺度标准作了修订, 即修订为TBB≤-32 ℃的连续冷云区直径≥20 km。根据马禹等的MβCS普查标准和该文修订的MβCS普查标准, 利用GOES-9卫星红外云图普查了2003年6月19日—7月22日淮河大水期间的MCS, 结果发现共有10个MαCS和24个MβCS, 并对24个MβCS作了普查标准修订前后的统计结果对比, 发现新的普查标准比根据马禹等的MβCS普查标准获得的结果多7个MβCS, 并且这7个MβCS中有6个都引起强降水, 因此这种对比分析结果表明:新MβCS普查标准对揭示淮河大水和MCS的关系更具合理性。此外, 还分析了3个因MβCS而引起局地强降水的典型个例, 这些MβCS的直径尺度只有几十至一百多公里, 不符合马禹等的MβCS普查标准。对这3个MβCS分析结果表明:该文新MβCS普查标准有助于对产生剧烈天气的MCS的普查研究和预报。     

Initiation and Evolution of Long-Lived Eastward-Propagating Mesoscale Convective Systems over the Second-Step Terrain along Yangtze-Huaihe River Valley

Based on the previous statistical analysis of mesoscale convective systems(MCSs)over the second-step terrain along Yangtze-Huaihe River Valley,eight representative long-lived eastward-propagating MCSs are selected for model-based sensitivity testing to investigate the initiation and evolution of these types of MCSs as well as their impact on downstream areas.We subject each MCS to a semi-idealized(CNTL)simulation and a sensitivity(NOLH)simulation that neglects condensational heating in the formation region.The CNTL experiment reveals convection forms in the region downstream of a shortwave trough typified by persistent southwesterly winds in the low-to midtroposphere.Upon merging with other convective systems,moist convection develops into an MCS,which propagates eastward under the influence of mid-tropospheric westerlies,and moves out of the second-step terrain.The MCS then merges with pre-existing local convection over the plains;the merged convection reinforces the cyclonic wind perturbation into a mesoscale vortex at 850 hPa.While this vortex moves eastward to regions with local vortex at 850 hPa,another vortex at 925 hPa is also intensified.Finally,the vortices at 850 and 925 hPa merge together and develop into a mesoscale convective vortex(MCV).In contrast,MCSs fail to form and move eastward in the NOLH experiment.In the absence of eastward-propagating MCSs,moist convection and mesoscale vortices still appear in the plains,but the vortex strength and precipitation intensity are significantly weakened.It is suggested the eastward-propagating MCSs over the second-step terrain significantly impact the development and enhancement of moist convection and vortices in the downstream areas.     

Impact of land–sea breezes at different scales on the diurnal rainfall in Taiwan

The formation mechanism of diurnal rainfall in Taiwan is commonly recognized as a result of local forcings involving solar thermal heating and island-scale land–sea breeze (LSB) interacting with orography. This study found that the diurnal variation of the large-scale circulation over the East Asia-Western North Pacific (EAWNP) modulates considerably the diurnal rainfall in Taiwan. It is shown that the interaction between the two LSB systems—the island-scale LSB and the large-scale LSB over EAWNP—facilitates the formation of the early morning rainfall in western Taiwan, afternoon rainfall in central Taiwan, and nighttime rainfall in eastern Taiwan. Moreover, the post-1998 strengthening of a shallow, low-level southerly wind belt along the coast of Southeast China appears to intensify the diurnal rainfall activity in Taiwan. These findings reveal the role of the large-scale LSB and its long-term variation in the modulation of local diurnal rainfall.     

亚洲季风区不同形态中尺度对流系统的特征分析

利用16 a的TRMM卫星观测资料,分析了亚洲季风区准圆状、线状和拉长状中尺度对流系统(MCSs)的空间分布、对流属性及其区域变化特征。结果表明:拉长状MCSs的数量最多,准圆状的其次而线状的最少。自西向东,准圆状(线状)MCSs数量占各区域MCSs总数的比例逐渐减小(增加),线状MCSs在副热带和洋面地区的产生几率相比更大。MCSs的发生频次呈现以暖季(5—9月)为峰值的单峰分布,准圆状和拉长状MCSs的暖季峰值比线状MCSs的大。MCSs主要发生在下午—傍晚时段,但线状MCSs在午夜—凌晨出现的概率比其它两种大。3种类型MCSs的整体强度基本表现为副热带地区弱于近热带地区,但不同类型MCSs的强度差异在各区域不尽相同,如中国中东部地区和西北太平洋地区的准圆状MCSs强度最强,但东海及其以东洋面的线状MCSs强度最强。     

Modes of Mesoscale Convective System Organization During Meiyu Season over the Yangtze River Basin

Mesoscale convective systems （MCSs） are classified and investigated through a statistical analysis of composite radar reflectivity data and station observations during June and July 2010-2012. The number of linear-mode MCSs is slightly larger than the number of nonlinear-mode MCSs. Eight types of linear-mode MCSs are identified： trailing stratiform MCSs （TS）, leading stratiform MCSs （LS）, training line/adjoining stratiform MCSs （TL/AS）, back-building/quasi-stationary MCSs （BB）, parallel stratiform MCSs （PS）, bro- ken line MCSs （BL）, embedded line MCSs （EL）, and long line MCSs （LL）. Six of these types have been identified in previous studies, but EL and LL MCSs are described for the first time by this study. TS, LS, PS, and BL MCSs are all moving systems, while TL/AS, BB, EL, and LL MCSs are quasi-stationary. The average duration of linear-mode MCSs is more than 7 h. TL/AS and TS MCSs typically have the longest durations. Linear-mode MCSs often develop close to the Yangtze River, especially over low-lying areas and river valleys. The diurnal cycle of MCS initiation over the Yangtze River valley contains multiple peaks. The vertical distribution of environmental wind is decomposed into storm-relative perpendicular and parallel wind components. The environmental wind field is a key factor in determining the organizational mode of a linear-mode MCS.     

2007年7月8—9日淮河流域特大暴雨过程MCS观测分析

利用多部雷达组合反射率因子拼图资料、地面自动站加密资料及NCEP 1°×1°每日4 次再分析资料,分析2007 年7 月8—9 日淮河流域特大暴雨过程中MCS 活动及其影响系统和降水特征。结果表明,该过程主要由3 次线状MCSs 活动造成,其分别为邻接层状单向发展MCS、前导层状MCS 和镶嵌带状MCS;雷达组合反射率因子图上,MCS 表现为回波组织性强、模态清晰,或移动,或静止,MCS 雷达回波分布特征决定雨带走向和落区;3 次MCSs 活动分别对应地面图上不同的天气影响系统,第一次邻接层状单向发展的MCS 主要受地面弱冷锋和低压倒槽影响,第二次前导层状降水MCS 受强的锋面影响,第三次镶嵌带状MCS 由地面风场上辐合线造成,与之对应的对流层中低层流场或高度场上表现为两次低涡活动,随低涡演变,MCS 生成区对应气流辐合区。     

The 2001 Mesoscale Convective Systems over Iberia and the Balearic Islands

Summary This paper characterizes Mesoscale Convective Systems (MCSs) during 2001 over Iberia and the Balearic Islands and their meteorological settings. Enhanced infrared Meteosat imagery has been used to detect their occurrence over the Western Mediterranean region between June and December 2001 according to satellite-defined criteria based on the MCS physical characteristics. Twelve MCSs have been identified. The results show that the occurrence of 2001 MCSs is limited to the August–October period, with September being the most active period. They tend to develop during the late afternoon or early night, with preferred eastern Iberian coast locations and eastward migrations. A cloud shield area of 50.000 km² is rarely exceeded. When our results are compared with previous studies, it is possible to assert that though 2001 MCS activity was moderate, the convective season was substantially less prolonged than usual, with shorter MCS life cycles and higher average speeds. The average MCS precipitation rate was 3.3 mm·h⁻¹ but a wide range of values varying from scarce precipitation to intense events of 130 mm·24 h⁻¹ (6 September) were collected. The results suggest that, during 2001, MCS rainfall was the principal source of precipitation in the Mediterranean region during the convective season, but its impact varied according to the location. Synoptic analysis based on NCEP/NCAR reanalysis show that several common precursors could be identified over the Western Mediterranean Sea when the 2001 MCSs occurred: a low-level tongue of moist air and precipitable water (PW) exceeding 25 mm through the southern portion of the Western Mediterranean area, low-level zonal warm advection over 2 °C·24 h⁻¹ towards eastern Iberia, a modest 1000–850 hPa equivalent potential temperature (θ_e) difference over 20 °C located close to the eastern Iberian coast, a mid level trough (sometimes a cut-off low) over Northern Africa or Southern Spain and high levels geostrophic vorticity advection exceeding 12·10⁻¹⁰ s⁻² over eastern Iberia and Northern Africa. Finally, the results suggest that synoptic, orographic and a warm-air advection were the most relevant forcing mechanisms during 2001.     

The contribution of mesoscale convective systems to intense hourly precipitation events during the warm seasons over central East China

Central East China is an area where both intense hourly precipitation(IHP) events and mesoscale convection systems(MCSs) occur frequently in the warm seasons. Based on mosaics of composite Doppler radar reflectivity and hourly precipitation data during the warm seasons(May to September) from 1 July 2007 to 30 June 2011, the contribution of MCSs to IHP events exceeding 20 mm h~(-1) over central East China was evaluated. An MCS was defined as a continuous or quasicontinuous band of 40d BZ reflectivity that extended for at least 100 km in at least one direction and lasted for at least 3h. It was found that the contribution of MCSs to IHP events was 45% on average over central East China. The largest contribution,more than 80%, was observed along the lower reaches of the Yellow River and in the Yangtze River–Huaihe River valleys.These regions were the source regions of MCSs, or along the frequent tracks of MCSs. There were two daily peaks in the numbers of IHP events: one in the late afternoon and one in the early morning. These peaks were more pronounced in July than in other months. MCSs contributed more to the early-morning IHP event peaks than to the late-afternoon peaks. The contributions of MCSs to IHP events with different intensities exhibited no significant difference, which fluctuated around 50% on average over central East China.     

A warm season climatology of mesoscale convective systems in the Mediterranean basin using satellite data

A 3-year climatology of isolated warm season mesoscale convective systems (MCSs) was built for the Mediterranean basin using Meteosat Second Generation infrared imagery and an objective identification and tracking algorithm. A dataset of 4,718 MCS trajectories was constructed for the warm season of the period 2005–2007, which in turn was split into two subsets (deep and weak convective) according to the intensity of convection using a discriminant parameter in the MCS properties. Several parameters related to geographical, temporal, radiative, morphological, and motion related properties were calculated for each MCS. The majority of MCSs are mainly continental and strongly correlated with orography showing an increased formation from April to June when maximum is found. Initiation and dissipation time revealed a distinct diurnal cycle having a strong correlation with the typical diurnal heating cycle of the atmosphere. On average, a typical isolated MCS in the Mediterranean basin initiates between 14:00 and 17:00 local solar time, tends to be small with elongated shape, short-lived, usually moving toward northeast to southeast with a mean velocity of 36 km/h. When comparing the two MCS subsets, some notable differences were revealed. Weak convective MCSs initiate earlier, move faster, travel longer, tend to reach slightly smaller sizes, are more linear, present higher cloud top temperatures, and have lower fractions of convective cloud type areas than deep convective systems.     

梅雨锋暴雨中尺度对流系统触发和组织化的观测分析

利用观测和NCEP再分析资料,对2015年6月26-28日江淮流域梅雨锋暴雨天气对流的触发和中尺度对流系统（MCS）的组织方式进行了分析。结果表明:梅雨锋附近发展的2个线状中尺度对流系统是暴雨的直接制造者。MCS2的发展有2种组织方式,26日夜间到27日凌晨,东西向雨带的不断后部建立和随后对流单体的列车效应是其发展的主要方式。27日凌晨到白天,初期新单体不断在线状MCS2的南缘触发,形成多个近乎平行的东北-西南向短雨带,后期梅雨锋锋面雨带从西部不断东移,经过强降水区;对流元有2种尺度的组织方式:新生对流单体沿着单个雨带向东北方向的列车效应以及东北-西南向雨带沿线状中尺度对流系统向东平移的"列车带"效应;持续的后部建立型和沿着同一路径不断的"列车带"效应使MCS2发展和维持。梅雨锋前不稳定空气的地形抬升和边界层辐合上升是初始对流的主要触发机制;26日夜间对流产生的冷池对对流的触发和MCS2的组织化及维持起重要作用,中尺度对流系统的组织特征和发生、发展受近地面环境场制约。      

内蒙古夏季典型短时强降水中尺度特征

利用常规观测资料、NCEP FNL分析资料、FY-2D逐时云顶亮温(TBB)资料、内蒙古地区自动气象站资料和闪电定位资料, 对2012—2015年内蒙古夏季37例典型短时强降水事件进行分析。结果表明:冷锋云系尾部、涡旋云系和暖湿切变云系中发展的中尺度对流系统(MCS)是造成内蒙古短时强降水的直接影响系统, 短时强降水发生在MCS发展或成熟阶段, 而且位于TBB梯度密集区MCS移出区域靠近干冷空气侵入一侧。自动气象站观测到的中气旋、中低压以及中小尺度气旋式辐合风场和切变线诱发MCS发展, MCS发展到成熟阶段地闪密度达到最大值, 地闪密度值较高对应的MCS面积扩展率也较大。内蒙古西部和中部偏北地区短时强降水发生前3 h相对湿度达到60%~80%, 但其余地区相对湿度基本为80%~90%, 温度锋区浅薄冷空气是触发MCS发生发展的关键因素。     

华南前汛期MCS的活动特征及组织发展形式

利用卫星云图Tbb资料、常规观测资料和NCEP/NCAR再分析资料,按照Jirak对中尺度对流系统(MCS)的分类方法,将华南MCS分为MCC(中尺度对流复合体)、PECS(线状或长条状MCS)、MβCCS和MβECS(即β尺度的MCC和β尺度的PECS)4种类型,对华南前汛期MCS的时空变化特征、发生发展的组织形式和天气学背景进行了分析。结果表明:PECS是华南地区MCS的主要发展形式。4—6月MCS的发生个数逐月增多。MCS的日变化呈单峰型,主要集中于下午到上半夜形成,傍晚到半夜之间发展成熟。但具体到不同的4种类型,其日变化特征有一定差异。MCS活动分布特征与地形没有明显对应关系,全区都可有PECS发生。MCS主要以东移为主,其次的移动方向4种不同类型分别略有不同。MCS的发生发展有3种主要天气形势:500 hPa槽前西南风场型、850 hPa切变线南侧的西南风场型和地面低槽配合的Ⅰ型;500 hPa西北风场型、850 hPa切变线型和地面低槽配合的Ⅱ型;500 hPa西风槽过境型、850 hPa切变线南侧的西南风场型和地面低槽配合的Ⅲ型。孤立发展和合并增长是华南MCS的主要组织发展形式。     

渤海湾西部海陆风的空间结构

利用常规气象观测资料、NCEP再分析资料与WRF数值模拟资料,以2014年8月11日闽东沿海一次大暴雨天气过程为例,分析了该过程中海风锋、低压环流的形成、移动及其在暴雨区上空的结构演变与热力、动力特征。结果表明:(1)该过程午后强降水的主要影响系统是海风锋,夜间强降水的主要影响系统是低压环流。(2)数值模式较好地模拟出海风锋的生消以及低压环流的形成和移动。海风能深入到内陆70~90 km,并与山谷风形成海风锋。在海风锋的前端是东南风和东北或西北风交汇的辐合带,对应其南侧海风气旋性曲率最大处,降水越强。(3)海风锋在向内陆推进的过程中呈现出湿度增大、湿层增厚、气温下降的特征;海风最强时刻对应低空辐合最强、地面降水最强;海陆气压差日变化与海陆温差呈反位相分布。(4)闽东沿海午后强降水主要由海风锋造成;夜间,再次增强的偏南气流与随冷空气南下的偏北气流汇合,激发气旋性涡度增大,使得低压环流强烈发展,导致闽东沿海夜间大暴雨。

     

中尺度对流系统中的湿中性层结结构特征

基于CloudSat卫星获得的高分辨率中尺度对流系统垂直剖面结构,结合大气参量相对湿度和相当位温的诊断分析,在低纬度、中高纬度地区、陆地或海洋以及不同天气形势下,发现了多个非常典型的中尺度对流系统(MCS)内部具有湿中性层结特征的个例.进一步利用静止卫星普查到的东亚地区MCS分布情况,结合NCEP再分析资料诊断MCS重心位置处大气状态廓线,利用大量的例子从统计的角度揭示了湿中性层结结构特征在MCS中存在的普遍性,并且从动力学和热力学的角度探讨了湿中性层结结构在MCS发生和发展中所起到的作用.     

大理苍山—洱海局地环流的数值模拟

利用耦合了湖泊模型的WRF_CLM模式模拟了秋季大理苍山—洱海地区的局地环流特征。结果表明:模式对近地面温度、风向、风速的模拟与观测基本一致,模拟结果能较好地再现该地区山谷风和湖陆风相互作用的局地环流特征。在秋季,大理苍山的谷风起止时间为08:00~17:00(北京时,下同),湖风起止时间为09:00~19:00。局地环流受高山地形及洱海湖面影响明显,山谷风形成早于湖陆风1 h,夜间山风、陆风强盛于白天谷风、湖风。白天苍山谷风与洱海湖风的叠加作用会驱动谷风到达2600 m的高度,而傍晚最先形成的苍山山风则会减弱洱海的湖风环流。夜间盆地南部在两侧山风、陆风的共同作用下,形成稳定而持续的气旋式环流。日出以后,对流边界层迅速发展,边界层高度逐渐增高。陆地17:00温度达到最高,边界层高度也达到峰值2000 m,之后逐渐降低。日落后形成稳定边界层,边界层高度在夜间基本保持在100 m。相对于陆地,湖面白天边界层高度低300 m,夜间边界层高度高100 m。     

A MASCOTTE-based characterization of MCSs over Spain, 2000–2002

A 3-year Mesoscale Convective Systems (MCSs) database, which extends from 2000 to 2002, has been built for the Iberian Peninsula and the Balearic Islands using the objective method MASCOTTE (MAximum Spatial COrrelation Technique). It was originally developed to track the evolution of convective systems over the Amazon region; after modifications, it is able to track MCS evolution even with an hour and a half of missed images and provides essential information of both dynamical and morphological characteristics of MCSs. MASCOTTE is tested against a visual and subjective method, and is found to offer advantages such as automation and a simple and efficient operation that make it very useful for building large MCS databases.Thirty-five MCSs were found between June and October, most of them originated along the Mediterranean coast and near the Pyrenees, showing an increasing occurrence from June to September, when the maximum is found. The regions most influenced by MCS occurrences are Balearic Islands, Valencia, Catalonia, Murcia and the Basque Country. The MCSs tend to be small, short-lived and linear, usually moving eastward or northeastward with low velocities.The MCSs-associated precipitation presents high variability, ranging from 80 to 0 mm h⁻¹ as maximum hourly records. Two different convective regions are identified based on MCS behavior in extreme precipitation events: Northern Spain (the Basque Country) with abundant and continuous precipitation regime but little MCS influence, and the Mediterranean coast, where precipitation is sporadic but much more intense.     

地形作用下低空急流的演变与强降水对流风暴系统的相互作用

利用天气雷达、地面加密雨量站降水资料、綦江流域五岔水文站水文资料以及ERA5再分析资料,对2020年6月19—22日綦江流域破历史记录洪水的降水时空分布特征、环流背景、水汽源地和中尺度对流系统发展演变特征进行了分析。结果表明：（1）此次过程是一次范围集中的持续性强降水过程,表现出明显的阶段性和日变化特征,可分为三个阶段,强降水主要发生在夜间。（2）持续性强降水发生在乌拉尔山地区冷低压东移引导冷空气南下到四川盆地东北部、中纬度低槽在四川东部-重庆-贵州一带长时间维持、西太平洋副热带高压稳定少动的环流背景下。（3）低空西南暖湿急流进一步加强了贵州北部至重庆南部的大气层结不稳定度,并将中国南海和孟加拉湾的水汽输送到綦江流域一带,为强降水产生和持续提供了丰富的水汽。（4）3个强降水阶段中尺度对流系统（MCSs）的发生发展表现为不同特征,第一阶段MCSs对应的雷达强回波呈近南北向,东移影响綦江流域,强降水持续时间较短;第二阶段MCSs呈西南—东北向,影响綦江流域时间较长,但回波强度较弱;第三阶段MCSs呈块状,成熟时期呈西西北—东东南向线状分布,具有“列车效应”,影响綦江流域时间更长、降水强度更大。

     

多云天气下海南岛海风环流结构的数值模拟

利用WRF-Noah耦合中尺度模式对海南岛2012年7月5日的多云海风个例进行三维高分辨率数值模拟,重点分析多云天气条件下复杂地形区域的海风环流结构及其演变特征。通过观测资料与模拟结果的对比发现,WRF模式能够合理地模拟出岛屿四周的海风演变特征。与少云海风日相似,多云海风日中全岛海风于12时开始形成,15时海风发展最为强盛,影响范围最广,18时全岛海风的辐合程度最强,海风辐合区是主要的潜在降水区域。对比山区与平坦地区的海风环流发现,山区海风环流强盛期为13—18时,而平坦地区海风环流强盛期为15—18时。复杂的山地对海风环流结构有直接和间接的影响:一方面在山地地形动力阻挡和抬升作用下,海风环流变得更加清晰完整,间接延长了海风环流的维持时间;另一方面局地地形热力作用形成的谷风环流与海风几乎同时产生和消亡,两者汇合后,谷风的瞬间加强会引起海风锋锋消,瞬间减弱会引起海风锋锋生;两者同相叠加会使得海风环流结构更加完整。相比之下,平坦地区的海风受到的地形动力和热力作用小,海风水平分布比较规则,海风环流垂直结构的变化主要取决于不同方向海风之间的相互作用。