共查询到19条相似文献，搜索用时 171 毫秒
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利用1979-2013年美国关岛联合台风警报中心(JTWC)孟加拉湾热带气旋数据以及美国国家环境预报中心和美国国家大气研究中心(NCEP/NCAR)发布的2.5°×2.5°再分析资料、0.5°×0.5°降水格点资料,分析了35年初夏(5月)17个北上孟加拉湾风暴活动期间青藏高原及其周边地区降水、大气环流、水汽和热量收支及其气候异常特征,探讨孟加拉湾风暴活动对青藏高原大气环流的可能影响。结果表明:初夏孟加拉湾风暴活动期间,我国降水主要分布在青藏高原南侧、西南和华南地区,并相对于初夏气候平均表现为正异常。风暴北上过程伴随南亚高压北上,南支槽加深,青藏高原切变系统活跃等环流特征。与初夏平均相比,青藏高原东南部大气上升运动异常增强。同时受北上孟加拉湾风暴水汽和热量输送影响,该区域视热源和视水汽汇呈正异常区,而风暴影响下垂直运动增强是其热量和水汽收支异常的主要原因。 相似文献
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青藏和伊朗高原热力异常与北疆夏季降水的关系 总被引：5，自引：1，他引：4
青藏高原和伊朗高原热力异常对其周边地区天气气候有重要影响,已有研究多关注东部季风区,而对干旱区关注较少.针对这一不足,利用美国国家环境预测中心/美国国家大气研究中心(NCEP/NCAR)再分析月平均资料和北疆43站降水资料,分析了1961-2007年5月青藏高原和伊朗高原地表感热异常与北疆夏季降水的关系.奇异值分解(SVD)分析发现,5月青藏高原地表感热与北疆夏季降水呈负相关,伊朗高原为正相关.青藏高原和伊朗高原感热异常的大尺度对比,要比仅考虑单一高原的感热异常与北疆夏季降水有更密切的联系.定义了一个热力差异指数来表征这种地表感热异常的对比程度,相关分析发现,当5月伊朗高原地表感热偏强,青藏高原地表感热偏弱时,500hPa中亚上空和贝加尔湖上空分别为异常气旋和反气旋环流,在二者共同作用下,新疆上空盛行异常的偏南气流,有利于低纬度的暖湿气流北上,形成有利于降水的环流形势,同时越赤道索马里急流偏强,低纬度水汽被接力输送至中亚和新疆地区,为降水的发生提供了有利的水汽条件.进一步分析发现,青藏高原热力异常主要影响中高层大气环流,伊朗高原则主要影响水汽通量输送. 相似文献
3.
青藏高原地区5月热力差异和后期夏季北疆降水的联系 总被引：2，自引：0，他引：2
基于美国国家环境预测中心/美国国家大气研究中心(NCEP/NCAR)再分析月平均资料和新疆70站降水资料,分析了1961~2010年5月青藏高原地区地表热力异常差异和新疆夏季降水的联系。奇异值分解(SVD)分析发现,当5月青藏高原视热源偏弱,高原西北部地区偏强时,北疆夏季降水偏多。定义了一个热力差异指数来表征两个区域热力异常的对比程度,发现考虑这种大尺度热力差异对比要比单一地区与区域气候有更为密切的联系。当热力差异指数为负时,即5月青藏高原视热源偏弱,其西北部视热源偏强时:(1)西亚副热带西风急流位置偏南;(2)500 h Pa中亚上空和贝加尔湖上空分别对应异常气旋和反气旋环流,在二者共同作用下,北疆上空盛行异常的偏南气流,有利于低纬度的暖湿气流北上,形成有利于降水的环流形势;(3)印度半岛上空为异常反气旋环流,中亚上空为异常气旋环流,形成北疆夏季降水水汽的两步型输送,阿拉伯海水汽被输送至中亚和新疆地区。偏相关分析发现,青藏高原热力异常主要影响对流层中高层大气环流和水汽输送的第二步环流条件,高原西北部热力异常则影响水汽输送的第一步环流条件。 相似文献
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青藏高原前期冬春季地面热源与我国夏季降水关系的初步分析 总被引：7，自引：0，他引：7
首先对青藏高原地表热通量再分析资料与自动气象站(AWS)实测资料进行对比, 结果表明: 相对于美国国家环境预报中心和国家大气中心20世纪90年代研制的NCEP/NCAR(Kalnay 等1996)和NCEP/DOE (Kanamitsu 等2002) 再分析资料, ECMWF(Uppala 等2004)资料在高原地区的地表热通量具有较好的代表性。进一步利用奇异值分解(SVD)方法分析了ECMWF资料反映的高原地面热源与我国夏季降水的关系, 发现前期青藏高原主体的冬季地面热源与长江中下游地区夏季降水量呈负相关, 与华北和东南沿海地区的夏季降水量呈正相关。而长江中下游地区夏季降水量还与春季高原南部的地面热源存在负相关、与高原北部的地面热源存在正相关。高原冬、春季地面热源场的变化是影响我国夏季降水的重要因子。 相似文献
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基于国家气候中心(NCC_CSM11)、美国国家环境预报中心(NCEP_CFS2)和欧洲中期天气预报中心(ECMWF_SYS-TEM4)三种模式产品资料,以及美国国家环境预报中心(NCEP)的大气环流再分析资料和云南、贵州及四川三省359个站点月降水资料,搜寻模式"有预测技巧的高影响关键区",使用逐步回归方法建立预测释... 相似文献
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本应用美国国家环境预报中心(NCEP)和国家大气研究中心(NCAR)提供的全球大气40年逐日再分析资料和月平均场资料集，运用气象领域中广泛使用的GRADS绘图系统，对其进行等值线分析及数据输出的介绍，对于进一步将这一资料应用到科研及业务工作中具有一定的指导作用。 相似文献
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自1990年以来,美国国家海洋和大气局(NOAA),国家环境卫星资料和信息服务中心(NESDIS)一直利用改进的甚高分辨率辐射仪(AVHRR)多个红外通道数据和非线性算法,提供卫星海面温度(SST)资料.该文从辐射传输方程入手来描述线性及非线性SST算法,阐明非线性算法比线性算法精确,并介绍了目前美国在这方面工作的进展. 相似文献
11.
基于1979～2019年日本气象厅提供的地表感热与大气环流再分析资料,美国国家海洋和大气管理局提供的月均海表温度数据和国家气象信息中心提供的月降水数据,分析了夏季伊朗高原感热和热带印度洋海温与同期塔里木盆地降水的可能联系。奇异值分解分析表明,两个地区热力异常均与塔里木盆地夏季降水联系紧密,可以通过影响500 hPa风场和水汽输送来调制塔里木盆地夏季降水的变化。当伊朗高原感热和热带印度洋海温均偏强（弱）时,对应中亚上空受异常气旋（反气旋）控制,蒙古高原上空为反气旋（气旋）控制,二者共同作用塔里木盆地上空盛行异常偏南（北）风,形成有利（不利）的动力条件;同时印度半岛上空受异常反气旋（气旋）环流控制,中亚上空为异常气旋（反气旋）,阿拉伯海水汽可（不可）由以上两个系统两步输送至新疆上空,导致盆地夏季降水整体偏多（少）。当伊朗高原和热带印度洋热力异常反相变化时,盆地降水空间差异性较大,部分区域降水偏多,部分地区降水偏少。 相似文献
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青藏高原冬春积雪异常与中国东部地区夏季降水关系的进一步分析 总被引：30，自引：0，他引：30
为了进一步分析青藏高原(下称高原)冬春积雪异常与中国东部地区夏季降水的关系,利用1957～1994年高原地区的实测雪深、1951～1994年6～8月中国东部地区226个均匀分布测站的实测月降水量,以及美国国家环境监测中心/国家大气研究中心(NCEP/NCAR)1958～1994年1～12月的再分析格点值资料,对比分析了高原冬、春季多、少雪年后期中国东部地区夏季(6～8月)降水分布和环流的平均特征,也分析了高原积雪影响的机理.分析结果表明:1) 平均来说,多雪年夏季长江及江南北部降水可偏多1～2成,华北和华南的降水则偏少1～3成;少雪年夏季江淮流域及湘、黔地区少雨,华北和华南多雨.2)高原冬、春积雪不仅影响了后期高原的热状况,而且影响了后期东亚大气环流的季节变化和南亚与东亚的夏季风环流. 相似文献
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Leonard M. Druyan Matthew Fulakeza Patrick Lonergan Erik Noble 《Meteorology and Atmospheric Physics》2009,105(3-4):191-210
The study examines results of dynamic downscaling of two global analyses: the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis II and the Global Forecast System final analysis (FNL). Downscaling to a 0.5° grid over West Africa and the adjacent Atlantic Ocean is accomplished by each of two regional models, the Regional Model, version 3 (RM3) of the Center for Climate Systems Research and the Weather, Research and Forecasting model (WRF). Simulations are for September 2006, the African Monsoon Multidisciplinary Analysis (AMMA) Special Observing Period #3 (SOP-3). The aim of this study is to exploit the increased spatial detail in the simulations and representations of climate fields by the regional models to analyze meteorological systems within the SOP-3 area of interest and time frame. In particular, the paper focuses on the regional models’ representations of the structure and movement of a prominent easterly wave during September 10–13th, the precursor of Tropical Storm/Hurricane Helene. It describes the RM3 simulated structure of the developing storm in terms of circulation, precipitation, vertical motion, cumulus heating rates, and cross-sections of wind and geopotential height anomalies. Simulated cumulus heating rates within the wave’s main precipitation area imply a lowering of the bases of active cumulus in the transition from the African continent to the Atlantic, indicating that the ocean environment promotes greater upward latent heat flux that in turn intensifies overlying storms. RM3 circulation, precipitation patterns, and storm trajectory are reasonably consistent with observational evidence. Experiments show that precipitation rates near 6°N over the eastern North Atlantic are sensitive to vertical thermal stability, such that they are enhanced by warmer in situ sea-surface temperatures (SSTs) and diminished by colder SSTs. However, prescribing colder SST causes increases in precipitation north of 9°N within areas of large scale upward vertical motion where rainfall rates are less sensitive to in situ SSTs. The evaluation of WRF indicates that its storm propagation is too fast over West Africa, where associated WRF precipitation rates are exaggerated, but its performance is improved over the Atlantic. 相似文献
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Relationships between the West Asian subtropical westerly jet and summer precipitation in northern Xinjiang 总被引：2，自引：1，他引：1
Yong Zhao MinZhong Wang AnNing Huang HongJun Li Wen Huo Qing Yang 《Theoretical and Applied Climatology》2014,116(3-4):403-411
The relation between the spatial and temporal variations of the West Asian subtropical westerly jet (WASWJ) and the summer precipitation in northern Xinjiang has been explored using the NCEP/NCAR reanalysis data and the summer precipitation data at 43 stations in northern Xinjiang during 1961 to 2007. Results show that the position of the WASWJ is more important than its strength in influencing the summer precipitation in northern Xinjiang. When the jet position is further south, the anomalous southwesterly flow crossing the Indian subcontinent along the southern foothill of the Tibetan Plateau is favorable for the southwestward warm and wet air penetrating from low latitudes into Central Asia and northern Xinjiang and more rainfall formation. Further analysis shows that the interannual variations of the jet position are well correlated with the Arctic Oscillation (AO). In the weak AO years, the middle to upper troposphere becomes colder than normal and results in an anomalous cyclonic circulation at 200 hPa over Western and Central Asia, which enhances the westerly wind over middle and low latitudes and leads to the WASWJ located further south. 相似文献
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Interdecadal shift in the relationship between the East Asian summer monsoon and the tropical Indian Ocean 总被引：7，自引：0，他引：7
In this work, the authors investigate changes in the interannual relationship between the East Asian summer monsoon (EASM) and the tropical Indian Ocean (IO) in the late 1970s. By contrasting the correlations of the EASM index (EASMI) with the summer IO sea surface temperature anomaly (SSTA) between 1953–1975 and 1978–2000, a pronounced different correlation pattern is found in the tropical IO. The SSTA pattern similar to the positive Indian Ocean Dipole (IOD) shows a strongly positive correlation with the EASMI in 1953–1975. But in 1978–2000, significant negative correlation appears in the northern IO and the IOD-like correlation pattern disappears. It is indicated that the summer strong IOD events in 1953–1975 can cause a weaker-than-normal western North Pacific (WNP) subtropical high, which tends to favor a strong EASM. In 1978–2000, the connection between the summer IOD and the WNP circulation is disrupted by the climate shift. Instead, the northern IO shows a close connection with the WNP circulation in 1978–2000. The warming over the northern IO is associated with the significant enhanced 500 hPa geopotential height and an anomalous anticyclone over the WNP. The change in the IO–EASM relationship is attributed to the interdecadal change of the background state of the ocean–atmosphere system and the interaction between the ENSO and IO. In recent decades, the tropical IO and tropical Pacific have a warmer mean SST, which has likely strengthened (weakened) the influence of the northern IO (IOD) on the EASM. In addition, due to the increase in the ENSO variability along with the higher mean equatorial eastern Pacific SST in 1978–2000, the influence of ENSO on the East Asian summer circulation experiences a significant strengthening after the late 1970s. Because the warming over the northern IO is associated with the significant warming in the equatorial eastern Pacific, the strengthened ENSO–EASM relationship has likely also contributed to the strengthened relationship between the northern IO and the EASM in 1978–2000. 相似文献
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Interdecadal Modulation of the Influence of La Nina Events on Mei-yu Rainfall over the Yangtze River Valley 总被引：2，自引：0，他引：2
The aim of this study was to investigate changes in the relationship between mei-yu rainfall over East China and La Nin a events in the late 1970s,a period concurrent with the Pacific climate shift,using meiyu rainfall data and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis.This relationship was modulated by the climate shift:Before the 1977/1978 climate shift and after the 1992/1993 climate shift,mei-yu rainfall levels were above normal in most La Nin a years,whereas during the period 1979-1991,mei-yu rainfall was usually below normal levels in La Nin a years.Both composite analyses and results from an atmospheric general circulation model show remarkable detail in terms of La Nin a’s impacts on mei-yu rainfall in the late 1970s due to the change in the mean climatic state over the tropical Pacific.After the late 1970s,the tropical Pacific SSTs were warmer,and the mean state of low-level anticyclone circulation over the western North Pacific (WNP) weakened.Superimposed on La Nin a-related cyclonic anomaly over the WNP,anticyclonic circulation weakened.Prior to the late 1970s,the mean state of low-level anticyclone circulation over the WNP was stronger and was less affected by La Nin a-related anomalous cyclones.Anticyclone circulation may have brought moisture to the Yangtze River valley,leading to above-normal rainfall. 相似文献
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Interannual and decadal variations of snow cover over Qinghai-Xizang Plateau and their relationships to summer monsoon rainfall in China 总被引：15，自引：4，他引：11
Interannual and decadal variations of winter snow cover over the Qinghai-Xizang Plateau (QXP) are analyzed by using monthly mean snow depth data set of 60 stations over QXP for the period of 1958 through 1992. It is found that the winter snow cover over QXP bears a pronounced quasi-biennial oscillation, and it underwent an obvious decadal transition from a poor snow cover period to a rich snow cover period in the late 1970’s during the last 40 years.It is shown that the summer rainfall in the eastern China is closely associated with the winter snow cover over QXP not only in the interannual variation but also in the decadal variation. A clear relationship exists in the quasi-biennial oscillation between the summer rainfall in the northern part of North China and the southern China and the winter snow cover over QXP. Furthermore, the summer rainfall in the four climate divisions of Qinling-Daba Mountains, the Yangtze-Huaihe River Plain, the upper and lower reaches of the Yangtze River showed a remarkable transition from drought period to rainy period in the end of 1970’s, in good correspondence with the decadal transition of the winter snow cover over QXP. 相似文献
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Mechanisms determining the tropospheric temperature gradient that is related to the intensity of the Asian summer monsoon are examined in an intermediate atmospheric model coupled with a mixed-layer ocean and a simple land surface model with an idealized Afro–Eurasian continent and no physical topography. These include processes involving in the influence of the Eurasian continent, thermal effects of the Tibetan Plateau and effects of sea surface temperature. The mechanical effect on the large-scale flow induced by the Plateau is not included in this study. The idealized land–sea geometry without topography induces a positive meridional tropospheric temperature gradient thus a weak Asian summer monsoon circulation. Higher prescribed heating and weaker surface albedo over Eurasia and the Tibetan Plateau, which mimic effects of different land surface processes and the thermal effect of the uplift of the Tibetan Plateau, strengthens the meridional temperature gradient, and so as cold tropical SST anomalies. The strengthened meridional temperature gradient enhances the Asian summer monsoon circulation and favors the strong convection. The corresponding monsoon rainbelt extends northward and northeastward and creates variations of the monsoon rainfall anomalies in different subregions. The surface albedo over the Tibetan Plateau has a relatively weak inverse relation with the intensity of the Asian summer monsoon. The longitudinal gradient of ENSO-like SST anomalies induces a more complicated pattern of the tropospheric temperature anomalies. First, the positive (negative) longitudinal gradient induced by the El Niño (La Niña)-like SST anomalies weakens (strengthens) the Walker circulation and the circulation between South Asia and northern Africa and therefore the intensity of the Asian summer monsoon, while the corresponding monsoon rainbelt extends northward (southward). The El Niño (La Niña)-like SST anomalies also induces colder (warmer) tropospheric temperature over Eurasia and warmer (colder) tropospheric temperature over the Indian Ocean. The associated negative (positive) meridional gradient of the tropospheric temperature anomalies is consistent with the existence of the weak (strong) Asian summer monsoon. 相似文献
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Summary Previous studies have highlighted the crucial role of sea surface temperature (SST) anomalies in the tropical Atlantic region
in forcing the summer monsoon rainfall over subsaharan West Africa. Understanding the physical processes, relating SST variations
to changes in the amount and distribution of African rainfall, is a key factor in improving weather and climate forecasts
in this highly vulnerable region.
Here, we present sensitivity experiments from a regional climate model with prescribed warmer tropical SSTs, according to
enhanced greenhouse conditions at the end of the 21st century. This dynamical downscaling approach provides information about
the nonlinear response of the atmosphere to oceanic heating. It has been suggested that the response is at least partly accounted
for by the linear theory of tropical dynamics, involving a Kelvin and Rossby wave response to a tropical heat source. We compute
the major modes of the linear Matsuno-Gill model for geopotential height and horizontal wind components and project the simulated
response patterns onto these linear modes, in order to evaluate to which extent the simple linear theory may explain the SST-induced
climate anomalies over Africa. A multivariate Hotelling T2 test is used to evaluate whether these anomalies are statistically significant.
Forcing the regional climate model by warmer SSTs leads to substantial climate anomalies over tropical Africa: Rainfall is
increases over the Guinea Coast region (GCR) and tropical East Africa, but decreases over the Congo Basin and the Sahel Zone
(SHZ). At the 850 hPa level, a trough develops over southern West Africa and the Gulf of Guinea, and is associated with stronger
surface wind convergence over the GCR. These changes in the atmospheric dynamics strongly project onto the leading modes of
the linear Matsuno-Gill model at various zonal wave numbers. The corresponding atmospheric heating pattern is highly reminiscent
of the simulated nonlinear model reponse. The T2 test statistics reveal that the SST forcing induces a statistically significant climate anomaly over tropical Africa if the
climate state vector is reduced by projecting the simulated data onto the leading 10 linear modes. It is also shown that the
linear response prevails in a long-term simulation with more realistic lower and lateral boundary conditions. Thus, linear
tropical dynamics are assumed to be a major physical process on the ground of the prominent SST-African rainfall relationship. 相似文献