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1.
为了探索春季强对流发生发展的机制,利用常规观测资料、MICAPS资料以及新一代多普勒天气雷达资料,采用天气学诊断方法,对2013年3月20日凌晨发生在浙中金华地区的一次大范围的强雷暴天气过程进行分析。结果表明:(1)高空槽和地面倒槽是此次强对流天气过程的主要影响系统;(2)高空三层为一致的西南急流,水汽输送强;(3)中低层急流附近存在强的垂直上升运动中心且几乎重合,500hPa到地面存在强的垂直风切变,动力条件好;(4)中低层深厚的暖平流与高层弱冷平流相互作用形成了上干冷、下暖湿的不稳定层结;(5)中层冷空气渗透,促使强对流进一步发展,风暴发展为中-β尺度飑线系统,但前沿无阵风锋产生;(6)飑线南段的超级单体风暴发展为非超级单体强风暴,在雷达图上表现为"弓形"回波,其顶点经过武义站时造成27.4m/s(10级)的瞬时大风;(7)VIL高值维持时间较短,不利于冰雹出现。 相似文献
2.
湖南电网严重冰灾天气成因分析 总被引：1，自引：0，他引：1
为研究2005年初和2008年初2次造成湖南电网严重冰灾的低温雨雪冰冻天气过程的成因,利用NCEP1°×1°全球再分析资料、地面常规气象观测资料及环流特征指数资料对过程期间高中低三层的水平和垂直结构进行了诊断分析,并分析了两次冰冻天气过程中各项环流特征指数与气温的相关性,结果表明:副高强度持续偏强,中层有暖层存在,850hPa与700hPa有明显的逆温层,700hPa强劲的西南急流,850hPa南北温差锋区的建立和维持,异常强大的冷高压长时间控制是造成两次冰灾过程的主要原因;地面降水、相对湿度、日平均气温、日最低气温、风向风速均与电线覆冰直径有关,温度垂直结构、环流指数和地形也与冰冻有一定关系。 相似文献
3.
四川盆地强暴雨过程诊断及中尺度分析 总被引：2，自引：1，他引：1
为了探索四川盆地暴雨天气发生发展的机制,利用云图和美国环境预报中心的全球再分析资料,针对2010年8月18—19日出现的暴雨过程进行环流形势、物理量场及中尺度特征分析,结果表明：暴雨过程中不断有低压槽东移,西太平洋副高西伸至盆地东部,暖湿气流通过低层绕流等方式进入盆地;在低层辐合高层辐散和热力不稳定的条件下,随着干冷空气入侵,对流运动异常强烈,促使强降水发生,湿位涡等值线密集带对暴雨落区预报有较好的指示意义。中尺度对流系统各阶段特征明显,与中尺度气旋演变有很好的相关性。 相似文献
4.
为了能够深入了解1011号台风"凡亚比"粤西暴雨过程发生发展机制,采用天气学诊断方法、Ncep1°×1°再分析资料和观测降水资料对凡亚比登陆后在广东西部地区造成的两次暴雨过程进行了研究。通过初步诊断分析得到以下结论:粤西暴雨二次增强的主要原因是强冷空气侵入和水汽输送增加,二次增强过程偏南风主导的水汽条件造成了暴雨增强。假相当位温的垂直剖面显示暴雨主要发生在等值线密集陡峭的区域,等值线的斜率增加对暴雨二次增强有指示作用。湿位涡在暴雨区为上正下负的垂直分布形式,对流层上层高值位涡向下传递,高层干冷空气与低层暖湿气流交汇促使降水增加。 相似文献
5.
An N-shape thermal front in the western South Yellow Sea (YS) in winter was detected using Advanced Very High Resolution Radiation
(AVHRR) Sea Surface Temperature data and in-situ observations with a merged front-detecting method. The front, which exists
from late October through early March, consists of western and eastern wings extending roughly along the northeast-southwest
isobaths with a southeastward middle segment across the 20–50 m isobaths. There are north and south inflexions connecting
the middle segment with the western and eastern wings, respectively. The middle segment gradually moves southwestward from
November through February with its length increasing from 62 km to 107 km and the southern inflexion moving from 36.2°N to
35.3°N. A cold tongue is found to coexist with the N-shape front, and is carried by the coastal jet penetrating southward
from the tip of the Shandong Peninsula into the western South YS as revealed by a numerical simulation. After departing from
the coast, the jet flows as an anti-cyclonic recirculation below 10 m depth, trapping warmer water originally carried by the
compensating Yellow Sea Warm Current (YSWC). A northwestward flowing branch of the YSWC is also found on the lowest level
south of the front. The N-shape front initially forms between the cold tongue and warm water involved in the subsurface anti-cyclonical
recirculation and extends upwards to the surface through vertical advection and mixing. Correlation analyses reveal that northerly
and easterly winds tend to be favorable to the formation and extension of the N-shape front probably through strengthening
of the coastal jet and shifting the YSWC pathway eastward, respectively. 相似文献
6.
余燕群 《成都信息工程学院学报》2013,(5):549-556
对2012年8月19～21日西藏持续性强降水天气过程的成因进行分析。利用加密地面观测资料、FY一2C卫星TBB资料、常规观测资料和NCEP 1°×1°再分析资料,对2012年8月19--21日西藏持续性强降水天气过程进行诊断和中尺度特征分析。此次强降水天气过程是在稳定的径向型环流背景下产生的,巴尔喀什湖附近东移南下的短波槽和500hPa低涡切变是造成此次降水过程的主要影响系统,西太平洋副热带高压边缘的西南暖湿气流为降水过程提供r有利的水汽条件;β中尺度对流云团的先后影响,为强对流发展提供了必要的热力、动力条件;而中层冷空气的侵入和强的垂直风切变加剧了大气层结的不稳定,为降水天气提供了有利的条件。该研究为西藏夏季降水的相关预报预测提供科学依据。 相似文献
7.
The thermal condition anomaly of the western Pacific warm pool and its zonal displacement have very important influences on climate change in East Asia and even the whole world. However, the impact of the zonal wind anomaly over the Pacific Ocean on zonal displacement of the warm pool has not yet been analyzed based on long-term record. Therefore, it is important to study the zonal displacement of the warm pool and its response to the zonal wind anomaly over the equatorial Pacific Ocean. Based on the NCDC monthly averaged SST (sea surface temperature) data in 2°×2° grid in the Pacific Ocean from 1950 to 2000, and the NCEP/NCAR global monthly averaged 850 hPa zonal wind data from 1949 to 2000, the relationships between zonal displacements of the western Pacific warm pool and zonal wind anomalies over the tropical Pacific Ocean are analyzed in this paper. The results show that the zonal displacements are closely related to the zonal wind anomalies over the western, central and eastern equatorial Pacific Ocean. Composite analysis indicates that during ENSO events, the warm pool displacement was trigged by the zonal wind anomalies over the western equatorial Pacific Ocean in early stage and the process proceeded under the zonal wind anomalies over the central and eastern equatorial Pacific Ocean unless the wind direction changes. Therefore, in addition to the zonal wind anomaly over the western Pacific, the zonal wind anomalies over the central and eastern Pacific Ocean should be considered also in investigation the dynamical mechanisms of the zonal displacement of the warm pool. 相似文献
8.
Wind measurements derived from QuikSCAT data were compared with those measured by anemometer on Yongxing Island in the South China Sea (SCS) for the period from April 2008 to November 2009. The comparison confirms that QuikSCAT estimates of wind speed and direction are generally accurate, except for the extremes of high wind speeds (>13.8m/s) and very low wind speeds (<1.5m/s) where direction is poorly predicted. In-situ observations show that the summer monsoon in the northern SCS starts between May 6 and June 1. From March 13, 2010 to August 31, 2010, comparisons of sea surface temperature (SST) and rainfall from AMSR-E with data from a buoy located at Xisha Islands, as well as wind measurements derived from ASCAT and observations from an automatic weather station show that QuikSCAT, ASCAT and AMSR-E data are good enough for research. It is feasible to optimize the usage of remote-sensing data if validated with in-situ measurements. Remarkable changes were observed in wind, barometric pressure, humidity, outgoing longwave radiation (OLR), air temperature, rainfall and SST during the monsoon onset. The eastward shift of western Pacific subtropical high and the southward movement of continental cold front preceded the monsoon onset in SCS. The starting dates of SCS summer monsoon indicated that the southwest monsoon starts in the Indochinese Peninsula and forms an eastward zonal belt, and then the belt bifurcates in the SCS, with one part moving northeastward into the tropical western North Pacific, and another southward into western Kalimantan. This largely determined the pattern of the SCS summer monsoon. Wavelet analysis of zonal wind and OLR at Xisha showed that intra-seasonal variability played an important role in the summer. This work improves the accuracy of the amplitude of intra-seasonal and synoptic variation obtained from remote-sensed data. 相似文献
9.
A case of a snowstorm at the Great Wall Station was studied using data of NCEP (National Centers for Environmental Prediction) analysis, in situ observations and surface weather charts. The storm occurred on August 29th,2006, and brought high winds and poor horizontal visibility to the region.It was found that the storm occurred under the synoptic situation of a high in the south and a low in the north. A low-level easterly jet from the Antarctic continent significantly decreased the air temperature and humidity.Warm air advection at high level brought sufficient vapor from lower latitudes for the snowstorm to develop.The dynamic factors relating to strong snowfall and even the developmentof a snowstorm were deep cyclonic vorticity at middle and low levels,the configuration of divergence at high level and convergence at low level, and strong verticaluplift. There was an inversion layer in the low-level atmosphere during the later phase of the storm.This vertical structure of cold air at low levels and warm air at high levels may have been important to the longevity of the snowstorm. 相似文献
10.
Structures and Evolutions of Explosive Cyclones over the Northwestern and Northeastern Pacific 总被引：1，自引：0，他引：1
In this study, the structures and evolutions of moderate(MO) explosive cyclones(ECs) over the Northwestern Pacific(NWP) and Northeastern Pacific(NEP) are investigated and compared using composite analysis with cyclone-relative coordinates. Final Operational Global Analysis data gathered during the cold seasons(October–April) of the 15 years from 2000 to 2015 are used. The results indicate that MO NWP ECs have strong baroclinicity and abundant latent heat release at low levels and strong upper-level forcing, which favors explosive cyclogenesis. The rapid development of MO NEP ECs results from their interaction with a northern cyclone and a large middle-level advection of cyclonic vorticity. The structural differences between MO NWP ECs and MO NEP ECs are significant. This results from their specific large-scale atmospheric and oceanic environments. MO NWP ECs usually develop rapidly in the east and southeast of the Japan Islands; the intrusion of cold dry air from the East Asian continent leads to strong baroclinicity, and the Kuroshio/Kuroshio Extension provides abundant latent heat release at low levels. The East Asian subtropical westerly jet stream supplies strong upper-level forcing. While MO NEP ECs mainly occur over the NEP, the low-level baroclinicity, upper-level jet stream, and warm ocean currents are relatively weaker. The merged cyclone associated with a strong middle-level trough transports large cyclonic vorticity to MO NEP ECs, which favors their rapid development. 相似文献
11.
Previous research has defined the index of the Indian-Pacific thermodynamic anomaly joint mode (IPTAJM) and suggested that
the winter IPTAJM has an important impact on summer rainfall over China. However, the possible causes for the interannual
and decadal variability of the IPTAJM are still unclear. Therefore, this work investigates zonal displacements of both the
western Pacific warm pool (WPWP) and the eastern Indian Ocean warm pool (EIOWP). The relationships between the WPWP and the
EIOWP and the IPTAJM are each examined, and then the impacts of the zonal wind anomalies over the equatorial Pacific and Indian
Oceans on the IPTAJM are studied. The WPWP eastern edge anomaly displays significant interannual and decadal variability and
experienced a regime shift in about 1976 and 1998, whereas the EIOWP western edge exhibits only distinct interannual variability.
The decadal variability of the IPTAJM may be mainly caused by both the zonal migration of the WPWP and the 850 hPa zonal wind
anomaly over the central equatorial Pacific. On the other hand, the zonal migrations of both the WPWP and the EIOWP and the
zonal wind anomalies over the central equatorial Pacific and the eastern equatorial Indian Ocean may be all responsible for
the interannual variability of the IPTAJM. 相似文献
12.
The summer weather characteristics of the Grove Mountain, East Antarctica, are presented based on the data obtained by Chinese National Antarctic Expedition (CHINARE) in January 1999. The result shows that the pattern of daily variation of temperature and the prevailing wind direction in Grove is similar to that of Zhongshan Station. However, the daily range of temperature and strong wind frequency are much higher than those of Zhongshan Station. The change of wind direction is close to the weather system that impacted the Grove Mountain. The warm and wet air from northern parts often causes the precipitation. The clear weather appears when controlled by eastern winds in January. 相似文献
13.
东亚副热带西风急流的时间演变特征及其与中国东部夏季降水的关系 总被引：3，自引：0，他引：3
为深入了解东亚副热带西风急流与中国天气系统之间的联系,利用1961-2007年美国国家环境预报中心（NCAR／NCEP）再分析月资料和同期中国596站的降水资料,运用经一纬向急流轴和区域平均两种定义方法分析了西风急流的时间演变特征及其与中国东部降水型的关系,结果表明：（1）两种方法对西风急流东西、南北位置转折时段的分析很接近,分别出现在20世纪80年代和70年代;对西风急流强度、南北位置周期的表征也很一致,分别为10-15年和5-10年。（2）当西风急流位置偏北（南）时,东部地区整层大气环流呈“南北上升中间下沉（南北下沉中间上升）”的形势,850hPa的流场和水汽通量输送都有利于华北地区（江淮河流）的降水,易于形成“南北多中间少（南北少中间多）”的雨带分布,推测这两种反相位雨型的间隔时间为2．5-5年;相比之下,急流东西位置和强度的周期性变化与东部局地降水存在一定联系。 相似文献
14.
Bohloul Alijani 《山地科学学报》2008,5(3):218-231
In order to examine the effect of the Zagros Mountains on precipitation, first, the annual and Seasonal rainfall indices （rain days frequency, rain amount, daily rainfall intensity, and heavy rains） from 43 stations in 1995 - 2004 between the 30° N to 35° N parallels over the mountain range were analyzed. Second, the effect of the Zagros Mountains was studied through the computation of the spatial correlations between the precipitation parameters and the topographic indices （station site elevation, station mean elevation within a radius of 2.5 km, mean elevation of 9 blocks along each of the eight Cartesian directions, and the elevation differences of these 9 blocks from the station mean elevation）. The results showed that in the cold season the maximal rainfall occurs on the upper range of west slope, while in warm season it spreads over the study area. The correlations between precipitation and elevation indices were positive on the north of the stations and negative on the south of the stations, that is, the higher elevations of the stations to the north force the uplifting of the moist air masses and increase rainfall at the stations, while the lower elevations to their south lead the movement of the moist air masses to the stations. This is due to the fact that these stations or slopes are exposed to the moist air masses coming from the Mediterranean Sea and the Persian Gulf. The heavy rain days and the summer sporadic rain events do not show significant correlations with the topographic indices. The findings indicate that the Zagros Mountains intensify the cold period frontal rains especially over the west slope and block the moist air masses from entering the interior parts of the country. Moreover, these mountains play a secondary role in creating rain days. But they are very important in the production of precipitation in the area. Therefore, their absence will decrease the amount of rainfall to their west and, in return, expand the dry climates of their west and east. 相似文献
15.
Relationship between the onset date of South China Sea (SCS) summer monsoon and the summer rainfall in Shandong Province was examined by comprehensive analysis to establish a conceptual model of the link. If the summer monsoon occurs earlier, the 500 hPa level would induce the teleconnection of Eurasian pattern in the summer (June-August), which indicates that the western Pacific subtropical high is displaced northward further than usual, the Siberian high is intensified and the Okhotsk low is deepened. Under such circumstance, Shandong, located in the west side of the subtropical high and in front of the mid-Siberia high, would be expected to have a wet summer because it is quite possible for cold and warm air to meet and interact with each other in Shandong. Statistical analysis revealed that the 500 hPa anomalies over Korea and Japan were sensitive to the SCS monsoon onset date and very important to precipitation in Shandong, and that the convective activities over the deep water basin in the SCS in 24-26 pentads significantly influenced the position of the ridge line of the western Pacific subtropical high. These findings yielded better understanding of the causative mechanisms involved in the precipitation generation, so that the knowledge gained can possibly be applied for long-lead forecast. 相似文献
16.
INTRODUCTIONThelargestlakeinMexicoandthirdlargestinLatinAmerica,ChapalaLake(approximately2 0°N) ,is 1 50 0mabovesealevel,measures 75× 2 5km ,hasaveragedepthof6m (maximumdepthcloseto 1 1m)andamountainchainalongitsnorthernandsouthernshores (Fig .1a) .TheLermaRiverflowsintoit;theSantiagoRiverflowsoutofit.Thebeautifullandscape,andwarmclimateconducivetobreezecirculationalongitsshore ;absenceofabrupttemperaturevariations,andthemoderateairhumidityat tractmanytouriststothelake .Manyretirees… 相似文献
17.
根据气象常规观测资料、湛江新一代天气雷达资料、CFL-08风廓线雷达资料及卫星云图,分析2012年4月20日粤西沿海特大暴雨的天气环流形势、能量场、对流不稳定度、水汽输送和辐合辐散等环境特征及物理量场特征。结果表明:这次暴雨过程粤西地区共经历两次强降水过程,分别是受飑线系统、以及高空槽和低空切变影响;西南低空急流的出现有利于粤西暴雨的形成、维持和发展;暴雨过程粤西上空垂直累积液水含量达25~30g/m2;暴雨期间风向随高度明显逆转,有冷平流输送;约2.0 km高度以下低空急流的下传和增强与暴雨的产生有密切关系;短时间内多普勒天气雷达的速度回波低层辐合区域远远大于辐散区域是可能产生强降水的标志。 相似文献
18.
Based on the temperature data along 34°N, 35°N and 36°N sections in August from 1977 to 2003, the structure and formation of the Southern Yellow Sea Cold Water Mass (SYSCWM) and its responses to El Nino events are analyzed. Results show that: (1) There exist double cold cores under the main thermocline along the 35°N and 36°N sections. Also, double warm cores exist above the main thermocline along the 36°N section. (2) Thermocline dome by upwelling separates the upper warm water into two parts, the eastern and western warm waters. Additionally, the circulation structure caused by upwelling along the cold front and northeastward current along the coast in summer is the main reasons of double warm cores along the 36°N section. The intermediate cold water is formed in early spring and moves eastward slowly, which results in the formation of the western one of double cold cores. (3) Position of the thermocline dome and its intensity vary interannually, which is related to El Nino events. However, the 相似文献
19.
Based on the monthly average SST and 850 hPa monthly average wind data,the seasonal,interannual and long-term variations in the eastern Indian Ocean warm pool(EIWP) and its relationship to the Indian Ocean Dipole(IOD),and its response to the wind over the Indian Ocean are analyzed in this study.The results show that the distribution range,boundary and area of the EIWP exhibited obviously seasonal and interannual variations associated with the ENSO cycles.Further analysis suggests that the EIWP had obvious l... 相似文献
20.
The Arctic vortex is a persistent large-scale cyclonic circulation in the middle and upper troposphere and the stratosphere. Its activity and variation control the semi-permanent active centers of Pan-Arctic and the short-time cyclone activity in the subarctic areas. Its strength variation, which directly relates to the atmosphere, ocean, sea ice and ecosystem of the Arctic, can affect the lower atmospheric circulation, the weather of subarctic area and even the weather of middle latitude areas. The 2003 Chinese Second Arctic Research Expedition experienced the transition of the stratosphereic circulation from a warm anticyclone to a cold cyclone during the ending period of Arctic summertime, a typical establishing process of the polar vortex circulation. The impact of the polar vortex： variation on the low-level circulation has been investigated by some scientists through studying the coupling mechanisms of the stratosphere and troposphere. The impact of the Stratospheric Sudden Warming （SFW） events on the polar vortex variation was drawing people＇s great attention in the fifties of the last century. The Arctic Oscillation （ AO）, relating to the variation of the Arctic vortex, has been used to study the impact of the Arctic vortex on climate change. The recent Arctic vortex studies are simply reviewed and some discussions on the Arctic vertex are given in the paper. Some different views and questions are also discussed. 相似文献