共查询到20条相似文献，搜索用时 140 毫秒
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甘肃春季一场罕见强霜冻、冻害天气的分析 总被引：1，自引：1，他引：0
对2004年5月3~5日的强霜冻天气,本文从前期大气环流形势的调整与演变、气候背景、天气特征等方面进行分析研究,并就T213客观预报对这次天气的预报进行了分析。对于今后进一步做好霜冻预报防灾减灾,具有一定的指导意义。 相似文献
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奇异值分解方法对降水的预测试验 总被引：5，自引：4，他引：5
SVD方法由于可以用来研究两个气象场的相互作用，本文将其与多元回归方法结合作短期气候预测试验，并用它对云南5月雨量与海温进行分解，客观地反映出海洋和大气的耦合关系，所选高相关区的预报因子物理意义清晰，并与多元回归模型进行了预测效果比较，从所作的6年预报试验和2年独立预报检验结果来看，效果较好，值得进一步研究应用。 相似文献
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广州首次"黑色暴雨"过程的分析 总被引：3，自引：1，他引：2
受高空槽和锋面影响,广州地区2003年5月14日下午出现了1次大暴雨天气过程,广州市首次发布了2000年以来最高等级的黑色暴雨警告信号。本文着重从大气环流背景、大气物理量场、云图特征和激发机制等进行分析,试图深化对此类大暴雨成因的认识,为暴雨预报提供帮助。 相似文献
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1引言从宏观上讲，全球大气运动是不可分割的统一整体运动。大气内部在各个纬带、各种尺度、各种频率的运动形式之间相互依存、相互制约、相互影响，按照大气动力学能量串级理论和能量频散原理，大尺度运动系统既可向小尺度系统转移能量，也可从小尺度系统获得能量。这样，各种尺度运动系统就会通过非线性相互作用引起大气环流形势的持续异常或急剧变化。天气、气候变化的直接原因是大气环流的变化或异常。从预报的角度讲，不同时效的预报要侧重考察相应长度的天气过程和长于预报时效的大型环流系统。天气尺度系统是短期预报的主要对象。而… 相似文献
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分析１９９８年６月造成柳州地区月雨量出现历史最大值,致使山洪暴发、洪涝严重的环流形势及其前期环流形势,认为洪涝的形成是大气环流异常发展变化的结果。由此,试选取前期天气气候变化的特征值为预报因子,作出６月洪涝有无的预报。 相似文献
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暴雨的成因相当复杂。一次区域性暴雨从酝酿到发生的整个过程,实质上是大气低层水汽输送,幅合上升导致对流不稳定能量释放的过程。低层大气运动与一定的大气环流背景相关联,因此,大气环流的调整转换往往是暴雨发生的先兆。这些先兆可以成为暴雨中期预报的着眼点。本文试用谐谱天气分析的方法,从大气环流的谐波参数谱变化分析大气超长波及长波演变与浙江暴雨过程的关系,并进一步寻求暴雨过程中期预报的依据。 相似文献
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青海省寒潮天气的气候特征、分型及其预报 总被引：2，自引：0，他引：2
统计1980－2000年（10－5月）共21年的冬半年青海省寒潮资料，应用天气学、动力学和统计学相结合的方法，对青海省寒潮天气的环流形势、冷空气活动路径和气候背景等方面进行了分析，建立寒潮天气档案，总结出预报青海省寒潮天气的天气和天气学和动力学的预报指标，采用最优子集回归方法建立客观、定量的寒潮预报方法。 相似文献
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前期大气环流和海温变化对云南汛期雨量的影响 总被引：8，自引：1，他引：7
分析了云南汛期6~8月雨量与前期1~5月北半球200、500、850hPa高度场和海温场(40°S～40°N,30°E～70°W)的相关关系,得到两个相关场中显著相关区的时空分布特征、尺度范围和相关场的波列结构。并进一步分析了与云南汛期雨量相关的环流系统的天气气候学意义,得到云南汛期雨量与前期高度场和海温场的遥相关关键区。分析结果表明:通过综合考虑高度场和海温场作为云南汛期雨量预报因子,使预报更具可靠的物理基础,并初步归纳出影响云南汛期雨量的物理概念模型。 相似文献
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STUDY ON THE VARIATION IN THE CONFIGURATION OF SUBTROPICAL ANTICYCLONE AND ITS MECHANISM DURING SEASONAL TRANSITION-PART I:CLIMATOLOGICAL FEATURES OF SUBTROPICAL HIGH STRUCTURE* 
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下载免费PDF全文 Climatological characteristics of subtropical anticyclone structure during seasonal transition are investigated based on NCEP/NCAR reanalysis data.The ridge-surface of subtropical anticyclone is defined by the boundary surface between westerly to the north and easterly to the south (WEB in brief).In Afro-Asian monsoon area,the subtropical high in troposphere whose ridgelines are consecutive in wintertime takes on relatively symmetrical and zonal structure,the WEB tilts southward with increasing height.In summer,the subtropical high ridgelines are discontinuous at low levels and continuous at upper levels,the WEB tilts northward from the bottom up.Under the constraint of thermal wind relation,the WEB usually tilts toward warmer zone.May is the period when subtropical high modality most significantly varies.The structure and properties of subtropical high during seasonal transition are different from area to area.A new concept "seasonal transition axis" is proposed based on formation and variation of the vertical ridge axis of subtropical anticyclone.The subtropical high of summer pattern firstly occurs over eastern Bay of Bengal in the beginning of May.then stabilizes over eastern Bay of Bengal,Indo-China,and western South China Sea in the 3rd pentad of May,it exists over the South China Sea in the 4th-5th pentad of May and establishes over central India in the 1st-2nd pentad of June.The three consequential stages when summer modal subtropical high occurs correspond to that of Asian summer monsoon onset,respectively.To a great extent,the summer monsoon onset over the Bay of Bengal depends on the reversal of meridional temperature gradient in vicinity of the WEB in upper troposphere.The meridional temperature gradient at middle-upper levels in troposphere can be used as a good indicator for measuring the seasonal transition and Asian monsoon onset. 相似文献
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季节转换期间副热带高压带形态变异及其机制的研究Ⅰ:副热带高压结构的气候学特征 总被引：30，自引：9，他引：21
利用NCEP/NCAR再分析资料研究了季节转换期间副热带高压结构的气候特征。在亚、非季风区 ,冬季副热带高压带是相对对称的 ,具有脊线连续的带状结构 ,脊面随高度增加向南倾斜 ;夏季副热带高压带中低层是间断的 ,高层是连续的 ,脊面随高度增加向北倾斜。副热带高压脊面倾斜受热成风关系的制约 ,总是倾向暖区。 5月份副热带高压形态变异最显著 ,不同地域副热带高压的结构、性质存在较大差异。夏季型副热带高压于 5月初首先出现在孟加拉湾东部 ,5月第 3候稳定建立在孟加拉湾东部、中南半岛及南海西部地区 ;5月第 4～ 5候在南海建立 ;6月第 1～ 2候在印度中部建立。夏季型副热带高压建立的 3个阶段与亚洲夏季风爆发的 3个阶段存在着较好的对应关系。孟加拉湾夏季风的建立在很大程度上取决于高空副热带高压脊面附近经向温度梯度的反转。对流层中上层副热带高压脊面附近经向温度梯度可以作为表征亚洲夏季风爆发的指标 相似文献
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L. Zubair 《Theoretical and Applied Climatology》2002,71(1-2):119-127
Summary Hourly measurements of surface winds at Sita Eliya (6° 58′ N, 80° 46′ E, 1860 m a.s.l.) located atop the North-South mountain ridge in Sri Lanka were analyzed to investigate the diurnal and seasonal variation
in the wind climate. Surface winds are dominated by the monsoon regimes, with Northeasterlies from November to January, Southwesterlies
from February to May and Westerlies and Northwesterlies from June to October. Through most of the year, the average wind speed
is around 6–8 m/s. However from June to August, it is around 10–14 m/s. Wind in June is gusty due the location of the low-level
Easterly jet over Sri Lanka. The wind undergoes a reversal in both zonal and meridional directions in March and November coincident
with the migration of the Inter-Tropical Convergence Zone. Notwithstanding the period from May to September being designated
as the Southwest monsoon, the wind is from West, South-West-West and North-North-West. During the Southwest monsoon, wind
speed during the night is nearly as high as that during the day. This anomalous diurnal variation in wind speeds may be related
to orographic influences. The high wind speeds at Sita Eliya, in conjunction with the moderate diurnal and seasonal variability
in wind speed, is suitable for wind-energy generation.
Received January 2, 2001 Revised May 26, 2001 相似文献
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This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere. 相似文献
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青藏高原复杂下垫面能量和水分循环季节变化特征分析 总被引：2，自引：2，他引：0
为深入认识青藏高原能量和水分循环季节变化,利用GSWP(Global Soil Wetness Project)、GLDAS(Global Land Data Assimilation System)、AMSR-E(Advance Microwave Scanning Radiometer-EOS)土壤湿度以及台站观测资料等多种数据,采用滑动t检验初步分析高原下垫面各物理量季节变化特征。结果表明:各物理量季节变化特征明显且联系密切。高原下垫面净短波辐射和感热通量在1月中旬显著开始增加,5~6月达到全年最高值。净长波辐射5月表现为高值,夏季表现为低值。地表潜热通量在1月显著开始增加,在夏季达到全年最高值。表层土壤3月开始输送热量到大气,9月大气开始向土壤表层传递热量;融雪3~5月加快,雪盖减少。降水和1 cm植被含水量在2月显著开始增加,1 cm土壤显著开始加湿,5~6月降水陡增,1 cm土壤湿度表现为峰值。1 cm植被含水量、植被蒸腾、总蒸散与降水在7~8月达全年最高值,1 cm土壤湿度在7月表出现为谷值,9月达全年第二峰值。10月下垫面温度转冷后,雪盖增加,土壤湿度逐渐减小。 相似文献
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Diagnostic techniques of CEOF, power spectrum and bandpass filter wave are applied in this paper to analyze the seasonal northward beating of the northern subtropical high using day to day geopotential fields of 2.5 × 2.5 at 500 hPa May through July in 1988 and 1991. It is concluded that it is globally observed that the subtropical high has northward beats that propagate westward; the source of beating mainly lies in the region of Arabian Sea and central Pacific and the sink in eastern Pacific; the seasonal beating is dominated by effects of the disturbance field; low frequency oscillation plays a key role in the beating and the westward propagation so that the difference in the latter in individual years is caused by the varying source of disturbance and the low frequency waves it excites. 相似文献
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Effects of the seasonal variation in thermohaline and wind forcing on the abyssal circulation are investigated by using an
ocean general circulation model. To isolate effects of the seasonality in the thermohaline forcing from those in the wind
forcing, we carry out three experiments with (1) annual-mean wind forcing and perpetual-winter thermohaline forcing, (2) annual-mean
wind forcing and seasonal thermohaline forcing, and (3) seasonal wind forcing and seasonal thermohaline forcing. The deep
water under the seasonal thermohaline forcing becomes warmer than under the perpetual-winter thermohaline forcing. Although
the perpetual-winter thermohaline forcing is widely used and believed to reproduce the deep water better than the annual-mean
forcing, the difference between the results of the perpetual-winter and the seasonal thermohaline forcing is significant.
The seasonal variation of the Ekman convergence and divergence produces meridional overturning cells extending to the bottom
because the period of seasonal cycle is shorter than the adjustment timescale by baroclinic Rossby waves. The heat transport
owing to those Ekman flows and temperature anomalies makes the upper water (0–200 m) colder at low to mid-latitudes (40S–40N)
and warmer at high latitudes. Also the deep water becomes warmer owing to the warming of the northern North Atlantic, the
main source region of North Atlantic Deep Water. The model is also synchronously (i.e., without acceleration) integrated with
seasonal forcing for 5400 y. A past study suggested that under seasonal forcing, a sufficient equilibrium state can be achieved
after only decades of synchronous integration following more than 10 000 y of accelerated integration. Here, the result so
obtained is compared with that of the 5400-y synchronous integration. The difference in the global average temperature is
as small as 0.12 °C, and most of the difference is confined to the Southern Ocean.
Received: 1 May 1998 / Accepted: 5 January 1999 相似文献
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S. K. Deb H. C. Upadhyaya O. P. Sharma A. Chakraborty 《Meteorology and Atmospheric Physics》2006,94(1-4):43-64
Summary Hindcasts for the Indian summer monsoons (ISMs) of 2002 and 2003 have been produced from an ensemble of numerical simulations
performed with a global model by changing SST. Two sets of ensemble simulations have been produced without vegetation: (i)
by prescribing the weekly observed SST from ECMWF (European Centre for Medium Range Weather Forecasting) analyses, and (ii)
by adding weekly SST anomalies (SSTA) of April to the climatological SST during the simulation period from May to August.
For each ensemble, 10 simulations have been realized with different initial conditions that are prepared from ECMWF data with
five each from April and May analyses of both the years. The predicted June–July monsoon rainfall over the Indian region shows
good agreement with the GPCP (observed) pentad rainfall distribution when 5 member ensemble is taken from May initial conditions.
The All-India June–July simulated rainfall time series matches favourably with the observed time series in both the years
for the five member ensemble from May initial condition but drifts away from observation with April initial conditions. This
underscores the role of initial conditions in the seasonal forecasting. But the model has failed to capture the strong intra-seasonal
oscillation in July 2002. Heating over equatorial Indian Ocean for June 2002 in a particular experiment using 29th May 12
GMT as initial conditions shows some intra-seasonal oscillation in July 2002 rainfall, as in observation. Further evaluation
of the seasonal simulations from this model is done by calculating the empirical orthogonal functions (EOFs) of the GPCP rainfall
over India. The first four EOFs explain more than 80% of the total variance of the observed rainfall. The time series of expansion
coefficients (principal components), obtained by projecting on the observed EOFs, provide a better framework for inter-comparing
model simulations and their evaluation with observed data. The main finding of this study is that the All-India rainfall from
various experiments with prescribed SST is better predicted on seasonal scale as compares to prescribed SST anomalies. This
is indicative of a possible useful seasonal forecasts from a GCM at least for the case when monsoon is going to be good. The
model responses do not differ much for 2002 and 2003 since the evolution of SST during these years was very similar, hence
July rainfall seems to be largely modulated by the other feedbacks on the overall circulation. 相似文献
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热带海表温度持续异常对东亚初夏大气环流的影响 总被引：3，自引：1，他引：3
利用NCEP/NCAR月平均海表温度及北半球大气环流分析资料,系统研究了热带海洋表面温度持续异常状况下东亚初夏（5、6月份）大气环流的异常特征.研究发现,暖海温年,南亚高压、西太平洋副热带高压明显偏强,冷海温年明显偏弱;暖海温年,欧亚大陆南支西风急流明显减弱北移,东亚大陆对流层低层温度偏高或接近常年,青藏高原近地面温度偏高,而冷海温年,东亚大陆对流层低层温度偏低,5月份青藏高原近地面温度偏低.研究表明,海表温度的持续异常对东亚初夏大气环流的季节转换有重要影响. 相似文献