西北太平洋夏季风的变化对台风生成的影响

研究了西北太平洋夏季风特征及其季风槽结构对台风生成的影响。当西北太平洋季风槽增强并向东扩展使季风加强时,西北太平洋的风速垂直切变、高低空辐散风、湿度和海温等都对台风的生成产生有利的影响,台风数明显比季风槽弱时多。而且对台风生成的位置也有很大的影响,即季风槽强时,台风的生成位置偏东,季风槽弱时台风的位置偏西。这表明西北太平洋夏季风主要是通过季风槽活动影响台风的生成。而夏季风的强弱对台风也有影响,在西北太平洋夏季风的活跃阶段,西北太平洋夏季风强时,台风生成的比较多,夏季风中断时台风生成的比较少。西北太平洋夏季风通过季风的季节内振荡对西北太平洋台风也有显著的影响。季节内振荡对台风生成的影响主要以30—60 d振荡为主。在这种低频振荡对流活动的湿位相时期台风生成个数明显多,干位相时期台风生成的少。而且低频振荡的西风位相也有利于台风生成,在东风位相时生成的台风少。另外,还研究了多台风期西北太平洋夏季的特征(群发性),发现在这些时期,存在强的季风槽,弱的垂直切变与充足的水汽供应。这表明西北太平洋台风时空的群发性与夏季风活动的异常密切相关。

西北太平洋夏季风的气候学研究

西北太平洋季风区(5°～25°N,120°～160°E)是亚洲-太平洋季风区与亚洲-澳大利亚季风区的一个重要部分,也是一个独立的季风区.文中对西北太平洋夏季风进行了气候学研究,发现西北太平洋夏季风的爆发发生在31候(6月上旬)前后.爆发后,夏季风经历了3次活跃-中断循环,每个循环都相应于独立的干期和湿期.第1个循环是从6月初到7月中旬,降水与低层西风的中心主要位于5°～10°N.第2个循环是7-下旬至9-下旬,降水与低层西风明显向东北方向移动,位于10°～20°N.这个循环是西北太平洋夏季风最强盛的时期.第3个循环是从9月末到10月末,降水与低层西风又向南退回到5°～10°N,达到了西北太平洋夏季风最弱的阶段.这个循环的结束也就预示着西北太平洋夏季风的结束.西北太平洋季风区有明显的季节内振荡(ISO),这种气候的季节内振荡(CISO)主要由30～60 d与10～20 d两种周期组成,但是主要以30～60 d的低频振荡为主.根据西北太平洋的对流和低层西风在不同位相分布的分析,可以看出西北太平洋的低频对流和西风是向西向北传播的.西北太平洋的季风降水、对流与西风的活跃-中断循环在很大程度上受30～60和10～20 d低频振荡的调制.

西北太平洋夏季风对中国长江流域夏季降水的影响

利用1979～2005年NCEP/NCAR的环流场再分析资料和降水资料,通过对季风期降水、大气环流、水汽输送及低频振荡等方面的分析,分别从时间和空间上分析了西北太平洋夏季风与中国长江流域夏季降水的联系。结果表明:(1)西北太平洋夏季风与中国长江流域夏季降水存在显著的负相关关系,在西北太平洋夏季风强盛时,副热带高压异常偏北,其西侧的偏南气流异常偏弱,使得我国长江流域形成低层异常环流及水汽输送的辐散区,从而造成长江流域夏季降水偏少;而在西北太平洋夏季风减弱的年份,西太平洋副高异常偏南偏西,在长江流域以南地区形成异常偏强的偏南风水汽输送,使得长江流域成为南、北距平风的汇合区,其上空对流活动异常活跃,非常有利于长江流域的降水。(2)东亚局地Hadley垂直环流在强、弱季风年也显著不同,在强季风年里,Hadley局地环流异常偏弱,长江流域上空出现的下沉运动距平,使得该地区降水减弱,而弱季风年则正好相反。(3)西北太平洋夏季风存在显著的气候平均的大气季节内振荡(CISO),在西北太平洋夏季风减弱时期,长江流域降水同时受到源自热带西北太平洋西传CISO和源自热带印度洋东传CISO的共同影响,可能造成了某种锁相关系,从而造成降水偏多;而在强季风年里长江流域只受由西太平洋西传的CISO的影响,不容易激发降水。

GAMIL1.0大气模式模拟的西北太平洋夏季风:阵风参数化方案的影响

本文分析了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG/IAP)发展的大气环流格点模式(GAMIL1.0)对1980~1999年西北太平洋夏季风的模拟,讨论了阵风参数化方案对模拟效果的影响。结果表明:GAMIL1.0能合理再现西北太平洋夏季风气候态和年际变率的主要特征,不足之处在于其模拟的平均态及年际变率的强度都较之观测偏弱。引入阵风参数化方案后,模拟得到明显改进:区域平均的气候态降水由5.71 mm/d增加到8.35 mm/d,与观测值9.11 mm/d更为接近;模拟的季风指数与观测的相关系数由0.66上升到0.82;年际变率的振幅也显著增强,与观测更一致;模拟的"季风—ENSO"关系与观测几乎完全一致。对潜热通量、加热率和辐散环流的分析表明:降水平均态的改进来自阵风方案带来的潜热通量增加,年际变率模拟的改进与平均态的改进有关。引入阵风方案后,暖池地区的表面风速增加、潜热通量增强、降水增加,平均态更接近观测;合理的平均态降水使得模式对El Ni^no型海温异常的响应更为合理。这在加热场、对流层上层的异常辐合中心上都有清楚体现。

西北太平洋夏季风对中国长江流域夏季降水及农业的影响研究

为了探究影响中国长江流域夏季降水的因素,研究了西北太平洋夏季风对中国长江流域夏季降水及农业的影响,并从中发现长江流域夏季降水的主要影响因素,以期作为洪涝灾害防治依据;探析了季风气候对中国长江流域农业发展的影响,有助于促进该区域农业发展。

亚洲-太平洋季风区的遥相关研究

亚洲—太平洋季风区各季风子系统间的相互作用对季风区甚至全球的气候变化都有非常显著的影响。文中根据国内外相关研究,重点分析和评述了在亚洲—太平洋季风区中4种季节内时间尺度的遥相关关系,清楚地揭示了印度夏季风、东亚夏季风和西北太平洋夏季风之间的相互作用。研究发现:(1)在亚洲季风爆发初期,印度夏季风的爆发相对于中国长江流域梅雨的开始存在相差大约两周的超前关系,形成从印度西南部经孟加拉湾到达中国长江流域及日本南部的遥相关型,即"南支"遥相关型。(2)在季风盛行期间,长江流域降水明显受热带西北太平洋夏季风的影响,与西北太平洋夏季风降水呈反相关关系,即当季风减弱时,长江流域夏季降水偏多。(3)与长江流域降水相反,华北雨季(7月第4候—8月第3候)则与西北太平洋夏季风降水呈正相关关系,当西北太平洋夏季风强时,西太平洋副热带高压异常偏北偏东,副高西南侧的异常东南水汽输送在中国华北地区上空辐合,给该地区降水偏多提供了充足的水汽条件。(4)华北夏季降水同时还与印度夏季风呈正相关关系,在夏季风盛行期间,形成由印度西北部经青藏高原到中国华北地区的西南—东北走向的遥相关型,即"北支"遥相关型。上述4种遥相关关系,反映了亚洲夏季风季节北推过程中,印度夏季风、东亚夏季风和西北太平洋夏季风子系统之间的关联。

一个区域海气耦合模式的发展及其在西北太平洋季风区的性能检验:不同大气分量的影响

本文基于一个国际通用的耦合器OASIS,将区域大气模式CREM(Climate version of Regional Eta Model)和RegCM3(Regional Climate Model version 3)分别与改进的普林斯顿区域海洋模式(POM2000)耦合,建立了一个区域海气耦合模式,并利用该耦合模式讨论了不同大气分量对耦合模式性能的影响.以1998年西北太平洋夏季风为模拟个例,结果表明,对降水而言,CREM和RegCM3耦合前后显示出显著不同的特征.较之控制试验(即不考虑海气耦合),耦合后CREM(RegCM3)模拟的海上降水显著增多(减少).上述降水变化与耦合模拟的海温场偏差不同有关:CREM(RegCM3)耦合后海温偏暖(偏冷),增加(减少)了海表蒸发,增加(减少)了海上降水.分析表明,控制试验中模式对海洋区域温湿垂直廓线的模拟偏差是导致耦合海温偏差的重要原因.CREM(RegCM3)模拟的低层大气偏暖偏湿(干冷),使得海表潜热偏少(多),低层大气层结较之观测更不稳定(稳定),导致低层云量偏少(多),到达海表的净短波辐射偏多(少).CREM(RegCM3)在观测海温强迫下对海表净热通量模拟偏少(多),相当于一个潜在的虚假热源(冷源).一旦开始海气耦合,该热源(冷源)会使模拟的SST升温(降温),产生暖(冷)偏差.温湿廓线的模拟偏差可能与两个大气模式对对流降水过程的描述不同有关.

全球各主要季风年际变化主周期在20世纪90年代前后差异的对比

季风降雨的变异和异常会对农业活动产生至关重要的影响,研究了季风的变异规律可以为农业活动提供有益的信息。对比全球各主要季风年际变化主周期在20世纪90年代前后的特征差异。结果表明,西北太平洋夏季风的年际变化主周期由20世纪90年代之前的准4年周期为主,转变为20世纪90年代之后的准2年周期为主。相反,印度夏季风由20世纪90年代之前的准2年周期为主转变为20世纪90年代之后的准4年周期为主。南非夏季风在20世纪90年代之后出现准4年周期的显著增强,与之相反的,澳洲夏季风在20世纪90年代之后出现准4年周期的显著减弱。与全球其他季风相比较,西北太平洋夏季风年际变化主周期在20世纪90年代的变异特征与El Nino-Southern Oscillation(ENSO)的年际变化主周期的变异特征一致。热带太平洋和大西洋之间跨洋盆相互作用的增强可能是引起西北太平洋夏季风在20世纪90年代以后准2年周期变化显著增强的重要驱动因素。

Impacts of monsoon break events in the western North Pacific on the cross-equatorial flows over the Maritime Continent

本文利用ERA5逐日再分析资料,探讨了1979-2020年间西北太平洋季风中断事件对海洋性大陆越赤道气流的影响.合成结果表明,西北太平洋季风中断事件会造成高,低空越赤道气流减弱,即高层南风异常,低层北风异常,与此相关的环流异常表现为西北太平洋高层气旋,低层反气旋的斜压结构。特别的是,西北太平洋季风中断对高空越赤道气流的影响更为显著,92%的季风中断事件都导致高空越赤道气流减弱,而只有70%的事件造成低空越赤道气流减弱,这是由于低空越赤道气流同时还受到赤道中东太平洋海温异常的调控.

太湖最高水位及其与气候变化、人类活动的关系

采用累积距平及非参数检验的方法，重点分析1954～1999年太湖最高水位的变化，及其与相关气候因子的关系。1954年以来，太湖最高水位变化大致以20世纪80年代初为界，此前下降，此后则上升。梅雨和热带气旋影响次数直接影响太湖最高水位的变化；Wilcoxon检验表明最高水位变化与西北太平洋夏季风指数之间联系密切，而最低水位与其关系则不明显。Kendall协和系数检验验证了太湖最高水位与各气候因子变化之间的一致性。80、90年代太湖最高水位不断上升且常常居高不下，人类活动起着重要的作用；从河网水系变化、湖泊围垦和土地利用变化等方面分析了人类活动对太湖水位变化的影响。结论认为，太湖最高水位上升仍然受控于气候变化因子；而人类活动则加剧了水位上升的情势，并在其中所起作用日益重要。

全国各省市气象科技期刊文章摘编(29)

1 中尺度模式和新一代天气雷达产品识别云降水方法《气象科学》2007年第4期胡雯安徽省气象科学研究所 230061降水潜力区的确定和可降水云的识别是科学预报降水强度和落区的关键之一。

Contrasting the Indian and western North Pacific summer monsoons in terms of their intensity of interannual variability and biennial relationship with ENSO

The intensity of interannual variability(IIV)of the monsoon and monsoon–ENSO biennial relationship(MEBR)were examined and compared for both the Indian summer monsoon(ISM)and western North Pacific summer monsoon(WNPSM)during 1958–2018.Covariability of the IIV and MEBR were identified for the two monsoons.When the MEBR was strong(weak),the IIV of the monsoon was observed to be large(small).This rule applied to both the ISM and WNPSM.Out-ofphase relationships were found between the ISM and the WNPSM.When the IIV and MEBR of the ISM were strong(weak),those of the WNPSM tended to be weak(strong).During the period with a stronger(weaker)ENSO–Atlantic coupling after(before)the mid-1980 s,the IIV and MEBR of the WNPSM(ISM)were observed to be stronger.The increasing influences from the tropical Atlantic sea surface temperature(SST)may trigger the observed seesaw pattern of the ISM and WNPSM in terms of the IIV and MEBR multidecadal variability.The results imply that tropical Atlantic SST may need to be given more attention and consideration when predicting future monsoon variability of the ISM and WNPSM.

Enhanced correlation between ENSO and western North Pacific monsoon during boreal summer around the 1990s

The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant correlation afterward.This observed interdecadal change around the 1990 s may be associated with more frequent occurrences of central Pacific(CP)El Nino and the interdecadal changes in ENSO-associated SST anomalies.During the post-1990 s period(the pre-1990 s period),highly noticeable tropical Atlantic(Indian)Ocean SST anomalies tend to co-occur with the summertime Nino3.4 SST anomalies.The concurrent tropical Atlantic(Indian)Ocean SST anomalies could constructively reinforce(destructively mitigate)the WNP monsoon circulation anomalies induced by the summertime Nino3.4 SST,thus boosting(muting)the correlation between summertime Nino3.4 SST and WNP monsoon.In addition,the faster decaying pace of preceding-winter El Nino after the 1990 s,which may have been mainly induced by the influences from the spring tropical North Atlantic SST anomalies,could also have contributed to the enhanced correlation between the summertime Nino3.4 index and WNP monsoon.These results suggest that the enhanced influences from the tropical Atlantic SST may have triggered the intensified correlation between summertime ENSO and WNP monsoon since the early 1990 s.

Does regional air–sea coupling improve the simulation of the summer monsoon over the western North Pacific in the WRF4 model?

A new regional coupled ocean–atmosphere model,WRF4-LICOM,was used to investigate the impacts of regional air–sea coupling on the simulation of the western North Pacific summer monsoon(WNPSM),with a focus on the normal WNPSM year 2005.Compared to WRF4,WRF4-LICOM improved the simulation of the summer mean monsoon rainfall,circulations,sea surface net heat fluxes,and propagations of the daily rainband over the WNP.The major differences between the models were found over the northern South China Sea and east of the Philippines.The warmer SST reduced the gross moist stability of the atmosphere and increased the upward latent heat flux,and then drove local ascending anomalies,which led to the increase of rainfall in WRF4-LICOM.The resultant enhanced atmospheric heating drove a low-level anomalous cyclone to its northwest,which reduced the simulated circulation biases in the stand-alone WRF4 model.The local observed daily SST over the WNP was a response to the overlying summer monsoon.In the WRF4 model,the modeled atmosphere exhibited passive response to the underlying daily SST anomalies.With the inclusion of regional air–sea coupling,the simulated daily SST–rainfall relationship was significantly improved.WRF4-LICOM is recommended for future dynamical downscaling of simulations and projections over this region.

Seesaw Pattern of Rainfall Anomalies between the Tropical Western North Pacific and Central Southern China during Late Summer

It is well known that suppressed convection in the tropical western North Pacific(WNP) induces an anticyclonic anomaly,and this anticyclonic anomaly results in more rainfall along the East Asian rain band through more water vapor transport during summer, as well as early and middle summer. However, the present results indicate that during late summer(from mid-August to the beginning of September), the anomalous anticyclone leads to more rainfall over central southern China(CSC), a region quite different from preceding periods. The uniqueness of late summer is found to be related to the dramatic change in climatological monsoon flows: southerlies over southern China during early and middle summer but easterlies during late summer. Therefore, the anomalous anticyclone, which shows a southerly anomaly over southern China, enhances monsoonal southerlies and induces more rainfall along the rain band during early and middle summer. During late summer,however, the anomalous anticyclone reflects a complicated change in monsoon flows: it changes the path, rather than the intensity, of monsoon flows. Specifically, during late summers of suppressed convection in the tropical WNP, southerlies dominate from the South China Sea to southern China, and during late summers of enhanced convection, northeasterlies dominate from the East China Sea to southern China, causing more and less rainfall in CSC, respectively.

The Coupled Model Predictability of the Western North Pacific Summer Monsoon with Different Leading Times

Leading time length is an important issue for modeling seasonal forecasts. In this study, a comparison of the interannual predictability of the Western North Pacific (WNP) summer monsoon between different leading months was performed by using one-, four-, and sevenmonth lead retrospective forecasts (hindcasts) of four coupled models from Ensembles-Based Predictions of Climate Changes and Their Impacts (ENSEMBLES) for the period of 1960 2005. It is found that the WNP summer anomalies, including lower-tropospheric circulation and precipitation anomalies, can be well predicted for all these leading months. The accuracy of the four-month lead prediction is only slightly weaker than that of the one-month lead prediction, although the skill decreases with the increase of leading months.

Optimal heat source for the interannual variability of the western North Pacific summer monsoon

Using 132-member experiments based on a linear baroclinic atmospheric model(LBM), this study investigates the optimal heat source forcing the interannual variability of the western North Pacific summer monsoon(WNPSM). The 132 members are forced by localized atmospheric heat sources distributed homogeneously over regions from 55°S to 55°N, each 10° latitude × 30° longitude in size. The atmospheric responses to all the heating constitute an ensemble to examine the relative contribution of each local heat source to the strength of the WNPSM. The result indicates that the combination of an atmospheric heating(cooling) source over the subtropical Northwest Pacific and a cooling(heating) source over the tropical Indian Ocean and the midlatitudes from China to the southern part of Japan is the pattern most effective at enhancing(weakening) the WNPSM.Besides, the optimal heat source pattern identified by the LBM simulations is similar to the observed atmospheric heating anomalies associated with WNPSM interannual variability. The results suggest that any external forcing that leads to a similar heating structure as the optimal thermal forcing pattern could lead to an anomalous WNPSM.

2003～2014年东北三省气溶胶光学厚度变化分析

利用2003~2014年MODIS-Aqua气溶胶光学厚度(AOD)产品、DMSP卫星夜间灯光时间资料和基本气象资料,分析我国东北三省(辽宁、吉林、黑龙江)大气气溶胶光学厚度年际变化及季节变化的空间分布特征.结果表明,东北三省多年平均AOD空间分布存在由大连、沈阳、长春和哈尔滨等城市构成的一个高值带,呈东北-西南走向,多年平均AOD值为0.4~0.8;东北三省植被覆盖率较高的东部和北部是AOD的低值区,多年平均AOD小于0.3;东北三省AOD季节变化为AOD春季到夏季升高,秋季下降,冬季再次升高.东北三省AOD年际变化特征为大部分低值地区呈减小趋势,但以沈阳、长春和哈尔滨为轴线的东北-西南走向的高值区域呈增大趋势,反映了近10多年出现的空气质量两极分化趋势.此外研究了东北三省年均AOD在强、弱西北太平洋夏季风年时的空间分布差异,受地面风场影响,AOD在强季风年时较弱季风年偏低.

The critical role of Indian summer monsoon on the remote forcing between Indian and Northwest Pacific during El Nio decaying year

Recent studies have found a connection between Indian Ocean Basin Warming and the anomalous Northwest Pacific Anticy- clone （ANPWA） during El Nifio decaying year. This study focuses on the necessary condition for this connection by using ob- servation and numerical simulation. The seasonal transition of the Indian Ocean sea surface wind is critical to the climatic ef- fect of Indian Ocean Basin Warming. When the South Asian Summer Monsoon reaches its peak, the background wind be- comes desirable for basin warming, which then affects the climate in the Northwest Pacific. Via the Kelvin waves and Ekman divergence, the wind anomalies exist in the lower atmosphere east of the Indian Ocean warm Sea Surface Temperature （SST） anomalies, and intensify and sustain the ANWPA throughout the E1 Nifio decaying summer. This impact plays an important role in the inter-annual variability of the East Asian Summer Monsoon.

Development and evaluation of a regional ocean-atmosphere coupled model with focus on the western North Pacific summer monsoon simulation:Impacts of different atmospheric components

A regional ocean atmosphere coupled model (ROAM) is developed through coupler OASIS3,and is composed of regional climate model RegCM3 and CREM (Climate version of Regional Eta Model) as its atmospheric component and of a revised Princeton ocean model (POM2000) as its oceanic component.The performance of the ROAM over the western North Pacific summer monsoon region is assessed by the case simulation of warm season in 1998.Impacts of different atmospheric model components on the performance of ROAM are investigated.Compared with stand-alone simulation,CREM (RegCM3) produces more (or less) rainfall over ocean area with inclusion of the air-sea coupling.Different biases of rainfall are caused by the different biases of SST derived from the coupled simulation.Warm (or cold) SST bias simulated by CREM_CPL (RegCM3_CPL) increases (or decreases) the evaporation at sea surface,then increases (or decreases) the rainfall over ocean.The analyses suggest that the biases of vertical profile of temperature and specific humidity in stand-alone simulations may be responsible for the SST biases in regional coupled simulations.Compared with reanalysis data,the warmer (or colder) and moister (or dryer) lower troposphere simulated in CREM (RegCM3) produces less (or more) sea surface latent heat flux.Meanwhile,the more unstable (or stable) lower troposphere produces less (or more) cloudiness at low-level,which increases (or decreases) the solar radiation reaching on the sea surface.CREM (RegCM3) forced by observed SST overestimates (or underestimates) the sea surface net heat flux,implying a potential warm (or cold) heat source.After coupling with POM2000,the warm (or cold) heat source would further increase (or decrease) the SST.The biases of vertical profile of temperature and specific humidity may be ascribed to the different representation of cumulus convection in atmospheric models.