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Xiaohua SHAO Tao WANG Yongjin WANG Hai CHENG Kan ZHAO Xinggong KONG 《Journal of Meteorological Research》2020,(2):325-335
We present a230Th-dated stalagmite oxygen isotope(δ^18O)record from Loushanguan Cave in the Yangtze River valley,China.The^δ18O record,if viewed as a proxy of the Asian summer monsoon(ASM)intensity,provides an ASM history for the early Holocene with clear centennial-scale variability.A significant approximately 200-yr cycle between 10.2 and 9.1 ka BP(before present,where"present"is defined as the year AD 1950),as revealed by spectral power analyses,is of global significance and is probably forced by the Suess or de Vries cycle of solar activity.Here,we explore a physical mechanism to explain the relationship between the solar activity and the ASM.A strong coherence between the ASM and El Ni?o–Southern Oscillation(ENSO)has been observed by performing crosswavelet analyses on this cycle.Our study suggests that a strong(weak)ASM state corresponds to a warm(cold)ENSO,which is consistent with modern meteorological observations but contrasts with previous studies on regions far from the Meiyu rainbelt.We argue that the centennial fluctuations of the ASM are a fundamental characteristic forced by the solar activity,with the ENSO variability as a mediator.The relationship between ENSO and the ASM displayed spatial heterogeneity on the centennial scale during the early Holocene,which is a more direct analogue to the observed modern interannual variability of the ASM. 相似文献
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Explosive cyclones(ECs)over two basins in the Northern Hemisphere(20°-90°N)from January 1979 to December2016 are investigated using ERA-Interim and Optimum Interpolation Sea Surface Temperature(OISST)data.The classical definition of an EC is modified considering not only the rapid drop of the central sea level pressure of the cyclone,but also the strong wind speed at the height of 10 m in which maximum wind speeds greater than 17.2 m s^-1are included.According to the locations of the northern Atlantic and northern Pacific,the whole Northern Hemisphere is divided into the"A region"(20°-90°N,90°W-90°E)and"P region"(20°-90°N,90°E-90°W).Over both the A and P regions,the climatological features of ECs,such as their spatial distribution,intensity,seasonal variation,interannual variation,and moving tracks,are documented. 相似文献
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A QUANTITATIVE STUDY FOR ABNORMAL FREEZING RAINS AND SNOWSTORMS IN SOUTHERN CHINA IN EARLY 2008 总被引：2，自引：1，他引：1
A quantitative diagnosis is carried out for the upward branch of a local meridional circulation over southern China(SC) during the abnormal snowstorms with severe freezing rain from 10 January to 3 February 2008.The diagnostic study shows that the upward branch is mainly associated with the zonal advection of westerly momentum and meridional temperature advection instead of the latent heating(which is commonly the dominant factor in many other storm cases).The corresponding weather analyses indicate that(1) the zonal advection of westerly momentum represents the effect of the upper-level divergence on the anticyclone-shear side in the entrance of a 200 hPa westerly jet with a westward deviation from its climatological location over southwestern Japan;(2) the meridional temperature advection represents the interaction between the mid-lower layer(850 to 400 hPa) warm advection over SC(ahead of temperature and pressure troughs with the latter trough deeper than the former in the Bay of Bengal) and cold advection over north China(steered by an underlying flow at 500 hPa);(3) the relatively weak vapor transport(compared to that of spring,summer and autumn) from the Bay of Bengal and the South China Sea to SC and the existence of a temperature inversion layer in the lower troposphere over SC diminish the effect of latent heating.With the significant increase of vapor transport after 24 January,the role of latent heating is upgraded to become the third positive contributor to the upward branch over SC. 相似文献
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INTERANNUAL VARIABILITY OF WINTER AND SPRING PRECIPITATION IN SOUTH CHINA AND ITS RELATION TO MOISTURE TRANSPORT 总被引：3，自引：3，他引：0
The interannual variability of winter and spring precipitation in South China(SC)and its relation to moisture transport are investigated by using the monthly precipitation data of NMIC,NCEP reanalysis datasets and NOAA ERSST analysis datasets from 1960 to 2008.The results show that winter and spring precipitation in SC is less than normal from the 1960s to the start of the 1970s and from the end of the 1990s to the present.Most of rainfall anomalies on the whole regional scale of SC is well in phase during winter and spring,and the frequency of persistent drought is higher than that of persistent flood.Seasonal variations of moisture transport differences of SC between persistent drought and flood events are observed:the differences in winter are characterized by moisture transport from Bay of Bangle(BOB)and South China Sea(SCS),while differences in spring are characterized by that from SCS and North China(NC).There are two types of Ni o3.4 sea surface temperature anomaly(SSTA)related to persistent winter and spring drought(flood)events in SC,which are positive SSTA next to Ni o4(Ni o3)and negative SSTA next to Ni o3(Ni o4).Moreover,the variations of moisture transport from BOB and SC have important effects on persistent drought/flood in SC when the Ni o3.4 index is in the positive phase,while those from western North Pacific(WNP)-SC in winter and those from Philippine Sea(PHS)-SC and NC in spring primarily contribute to persistent drought/flood events in SC when the Ni o3.4 index is in the negative phase,and these stronger(weaker)moisture transports are observed in persistent flood(drought)during winter and spring regardless of the Ni o3.4 index.In conclusion,with the correlation between variations and distributions of Ni o3.4 SSTA and persistent drought/flood events in SC,moisture transport is responsible for the formation of precipitation anomalies.In addition,the moisture transport from SCS is most significantly correlated with persistent drought/flood events during winter and spring. 相似文献
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引言:最近十年来國内的氣象事業在高空探測方面發展得相當可觀。尤其測風氣球觀測站設立得最多,主要的原因是國内航空事業的進步。航空事業愈進步,牠所需要的氣象資料愈迫切。七七事變未發生以前,國内幾個有名的航空公司在其航線中主要的起落地點,曾設立幾個測風氣球觀測站,其中有觀測時間繼續了五,六年之久的。這種記錄相當可貴,而且似乎還很少人用牠来作過綜合的統計研究。中央研究院氣象研究所在南京,北平,西安,青岛觀象台在靑島,外人在上海與香港,也有較長時期的測風氣球記錄。那些記錄已經多人利用作過各方面的研究。研究結果散見國内外各氣象刊物。七七事變以来,由於空軍方面的需耍,在内地設立了不少的測風氣球 相似文献
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Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isentropic mass circulation(IMC)perspective.Results show that the midlatitude cold surface temperature anomalies always co-occurred with the high-latitude warm anomalies,and this was closely related to the strengthening of the low-level equatorward cold air branch of the IMC,particularly along the climatological cold air routes over East Asia and North America.Specifically,the two cold surges over East Asia in early winter were results of intensification of cold air transport there,influenced by the Arctic sea ice loss in autumn.The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures(SSTs)explained the concurrent anomalous warmth there.This enhanced a wavenumber-1 pattern and upward wave propagation,inducing a simultaneous and long-lasting stronger poleward warm air branch(WB)of the IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming(SSW)event on 4 January.The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch,hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February.Results do not yield a robust direct linkage from La Ni?a to the SSW event,IMC changes,and cold events,though the extratropical warm SSTs are found to contribute to the February cold surge in North America. 相似文献
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The relative contributions of atmospheric fluctuations on 6 h?2 d,2?8 d,and 8 d?1 month time scales to the changes in the air?sea fluxes,the SO circulation,and Antarctic sea ice are investigated.It was found that the imposed forcing variability on the three time scales creates a significant increase in wind power input,and hence an increase of about 50%,97%,and 5%of eddy kinetic energy relative to the simulation driven by monthly forcing,respectively.Also,SO circulation and the strength of the upper cell of meridional overturning circulation become strengthened.These results indicate more dominant effects of atmospheric variability on the 2?8 d time scale on the SO circulation.Meanwhile,the 6 h?2 d(2?8 d)atmospheric variability causes an increase in the total sea-ice extent,area,and volume,by about 33%,30%,and 19%(17%,20%,and 25%),respectively,relative to those in the experiment forced by monthly atmospheric variables.Such significant sea-ice increases are caused by a cooler ocean surface and stronger sea-ice transports owing to the enhanced heat losses and air-ice stresses induced by the atmospheric variability at 6 h?2 d and 2?8 d,while the effects of the variability at 8 d?1 month are rather weak.The influences of atmospheric variability found here mainly result from wind fluctuations.Our findings in this study indicate the importance of properly resolving high-frequency atmospheric variability in modeling studies. 相似文献
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上海市大气降尘污染的地面气象背景特征 总被引：10，自引：0，他引：10
对上海市11 a(1993-2003年)的月降尘量和同期气象要素资料分析表明,降尘量的年际变化呈下降趋势、月际变化呈双峰型分布,气象因子是这种分布的主要影响因素;重点运用聚类分析方法将降尘地面气象背景分为A、B、C、D、E 5个类型,不同天气类型对降尘量的影响不同,其中A型最有利于降尘,其气象特征是偏南风频率、3 m/s以上风速频率、蒸发量和气温位居其他各类之首,降水量、雨日数、湿度中等,气压低.冬季,降水与降尘量呈现为一定的正相关关系. 相似文献
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一次江淮暴雨中中尺度低涡的数值模拟及分析 总被引：6，自引：3，他引：6
利用MM5模式对2003年7月4—5日一次江淮梅雨暴雨过程进行了数值模拟。分析表明：暴雨与江淮地区对流层中低层中尺度低涡的发生发展有密切关系。中尺度低涡与中尺度雨团相伴移动，低涡强度与雨强的演变近于一致；低涡中心的强上升运动及低层辐合、高层辐散的配置有利于中尺度对流系统的发生发展；低涡低层有不稳定能量的积聚。应用螺旋度理论分析指出，较大的螺旋度是对流层中低层低涡发生和发展的一种有利机制。 相似文献
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一次局地大暴雨过程的数值模拟和诊断分析 总被引：14，自引：0，他引：14
采用中尺度数值模式MM5(V3)对2002年8月15-16日发生在江苏启东附近的一次局地大暴雨过程进行了数值模拟,较好地模拟出了本次过程的暴雨中心落区和降水量,以及相关的中尺度系统的发生、发展过程.探讨了中尺度涡旋、局地环流对这次暴雨过程的影响,结果表明,中尺度涡旋对暴雨的发生起了至关重要的作用,局地环流的存在,也有利于降水的发生. 相似文献
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"99.8"山东特大暴雨形成机制的数值模拟分析 总被引：11，自引：9，他引：11
利用双重嵌套的非静力数值模式MM5V3,成功地模拟了1999年8月11~12日山东诸城发生的特大暴雨。利用模式输出的高时空分辨率资料,对这次暴雨天气及中尺度低涡的形成机制进行了诊断分析。结果表明,这次特大暴雨是在弱冷空气侵入台风低压环流,热带辐合带北伸的形势下形成的;倾斜涡度发展是特大暴雨及中尺度低涡产生、发展的重要机制,鲁东南有利的地形对中尺度低涡的形成具有重要作用;台风低压倒槽顶部的强辐合作用首先触发上升运动,产生强降水,强降水位于低层气旋性暖式切变最明显的地方;强降水释放的凝结潜热使高层气层增暖,高层辐散加强,引起低层中尺度低涡强烈发展,导致降水增幅。可见,CISK机制是特大暴雨和中尺度低涡加强的另一种机制。 相似文献
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贵州大暴雨个例形成机制数值模拟 总被引：1，自引：0，他引：1
利用3层嵌套的中尺度数值模式MM5 V3.5,模拟了2007年6月24～25日发生在贵州中南部的一次大暴雨过程.利用模式输出的高分辨率资料,对这次暴雨天气及中尺度低涡的形成机制进行了诊断分析.模式较成功地模拟出了中尺度系统的演变和降水的分布特征.中尺度低涡的发展、稳定维持是造成贵州这次大暴雨天气的直接原因.暴雨、大暴雨出现在低涡的西南侧.在低层正涡度、辐合、强烈的上升运动和高层负涡度、辐散的有利配置下,形成深厚的上升运动柱,这种中尺度动力配置结构,不仅与暴雨区和暴雨发生时段相对应,而且是引起此次暴雨的中尺度低涡发展和持续的动力机制之一.暴雨区与强烈上升运动区,正涡度区相对应. 相似文献
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利用NCEP1°×1°再分析资料、卫星云图TBB资料和逐小时地面降水资料对2012年7月12~13日发生在湖北东部地区一次大暴雨过程进行了分析,结果表明:(1)在华北横槽转竖带动冷空气南下的过程中,中低层有中尺度低涡的发生发展,中尺度低涡的稳定维持与副高外围西南暖湿气流共同作用,导致了这次强降雨的发生。(2)鄂东强降水主要由两个中尺度暴雨云团影响,前一个暴雨云团为MCC,受副高外围西南气流向偏东方向移动,后一个暴雨云团受冷空气影响向东南方向移动。(3)低层露点锋与本次强降水天气过程的发生发展有较好的对应,锋区北侧偏北气流穿越露点锋,使得低层气旋式涡度增大、辐合加强。(4)本次过程干湿空气的相互作用形成能量锋区,锋区的维持和加强导致了强降水的发生。 相似文献
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江西一次暴雨过程的诊断分析 总被引：3，自引：0，他引：3
利用NCEP 1°×1°再分析资料、地面与探空资料、卫星资料等,对2012年5月12日发生在江西省中部的一次暴雨过程进行诊断分析。结果表明：本次暴雨过程发生在冷锋南侧地面倒槽区,由高层西风槽、低层低空急流及切变线、低涡共同影响所致。中低层西南气流的加强,一方面使暴雨区有充足的水汽输送,同时也使该区对流不稳定度加大,加强了暴雨区上空的对流上升运动。中尺度辐合线是强对流暴雨的触发机制,而冷锋影响使地面东风气流加强,冷空气入侵致中尺度辐合线演变为中尺度低压,中尺度低压是江西短时强降水长时间持续的机制;500hPa高空槽东移,槽前正涡度平流向江西上空输送,利于低层低涡生成和维持、上升运动加强,从而导致降水增强。冷空气影响初始阶段,〉10mm·h-1 的中尺度雨团产生在中尺度辐合线及其所演变成低压的1、2象限即中尺度辐合线或中尺度低压偏北一侧,随着冷空气的进一步入侵,中尺度雨团产生于中尺度低压的偏南一侧。 相似文献
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江淮梅雨锋强暴雨低涡系统发生发展的数值研究 总被引：16，自引：2，他引：14
利用美国新一代中尺度WRF(Weather Research and Forecast)模式,采用高分辨率的细网格距和适当的物理方案,对2003年7月4—5日的江淮梅雨锋强暴雨中尺度系统进行了数值模拟研究。模拟结果很好地描述了本次暴雨及其中尺度系统发生、发展的时空演变过程,并较理想地预报出了该次降水的落区、强度及降水中心的位置。着重分析了低空急流、倾斜不稳定发展及中尺度低涡系统和对流层高层小扰动,并进一步指出了其形成、发展的物理机制。从数值模拟分析结果看,倾斜垂直涡度的发展是造成低空涡旋生成和发展的动力机制。充足的湿有效能量和凝结潜热的释放为本次大降水过程提供了物质条件。 相似文献
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2003年淮河汛期一次中尺度强暴雨过程的诊断分析和数值模拟研究 总被引：11，自引：4，他引：11
2003年7月4—5日淮河流域发生了一次中尺度强暴雨过程,致使淮河洪水泛滥。这次暴雨过程由中尺度对流系统(MCS)以及因其发展而产生的低涡造成。通过对此次过程的诊断分析和新一代细网格WRF中尺度预报模式的数值模拟,研究了这次过程发生发展的机制。模拟结果较好地描述了本次暴雨及中尺度系统发生、发展的时空演变过程。分析结果表明:此次移动性暴雨过程的前期由不断向东移动发展的MCS造成,后期降水则由低涡切变线产生的中尺度低涡引起。同时,副热带高压明显偏西偏北,并维持较长时间,造成雨带一直维持在淮河流域。高层辐合中心的加强使低空急流不断增强,低空急流的增强进而引起低层辐合的加强,而低层辐合的加强以及上升运动的潜热释放导致低涡的发生,低涡形成及形成后移动缓慢,造成了淮河流域的大暴雨。高层中尺度辐散区的抽吸对低层中尺度涡旋的发生发展起到了促进和加强的作用。低层的中尺度辐合场和高层的中尺度辐散场的发展与耦合对中尺度系统的发展有很好的预示作用。低层中尺度辐合区的减弱预示着系统的衰减,西南偏西的中层相对干冷空气侵入并在梅雨锋前缘下沉促进了系统的衰减。 相似文献
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A Cloud-resolving Study on the Role of Cumulus Merger in MCS with Heavy Precipitation 总被引：4，自引：0，他引：4
The cumulus merging processes in generating the mesoscale convective system （MCS） on 23 August 2001 in the Beijing region are studied by using a cloud-resolving mesoscale model of MM5. The results suggest that the merger processes occurred among isolated convective cells formed in high mountain region during southerly moving process play critical role in forming MCS and severe precipitating weather events such as hailfall, heavy rain, downburst and high-frequency lightning in the region. The formation of the MCS experiences multi-scale merging processes from single-cell scale merging to cloud cluster-scale merging, and high core merging. The merger process can apparently alter cloud dynamical and microphysical properties through enhancing both low- and middle-level forcing. Also, lightning flash rates are enhanced by the production of more intense and deeper convective cells by the merger process, especially by which, the more graupel-like ice particles are formed in clouds. The explosive convective development and the late peak lightning flash rate can be found during merging process. 相似文献
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利用LAPS系统融合分析资料对安徽沿淮一次短时暴雨过程进行中尺度天气分析,探讨降水过程成因机制及天气结构特点,同时验证LAPS分析资料的实用性。结果表明：过程主要影响系统为中尺度气旋式涡旋,其向安徽北部沿淮地区移动为暴雨的发生、发展提供了触发机制。雷达降水回波主要出现在850hPa中尺度涡旋南侧以及700hPa槽前西南气流辐合上升运动过程中,持续的低空急流及其带来的水汽共同为暴雨过程提供了水汽条件和动力机制。比较雷达回波发展和云中液态水含量演变发现,云中液态水含量极大值区多出现在雷达回波单体的新生区域,借助于LAPS云中液态水含量分布结果对预测雷迭回波发展趋势及降水分布有借鉴作用。 相似文献