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1.
Mid-latitude atmospheric responses to heat and vorticity forcing using a linear baroclinic model 总被引：1，自引：0，他引：1
Based on diagnostic analysis of reanalysis data for 58-year, the distribution characteristics of decadal variability in diabatic heating, transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature (SST) anomalies over the North Pacific, as well as their relationship with anomalous atmospheric circulation have been investigated in this paper. A linear baroclinic model(LBM) was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies, and then to compare relative roles of different kinds of forcing in terms of geopotential height responses. The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic. The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow, as well as to the vertical profile of heating. The response to the idealized deep heating over the eastern North Pacific, mimicking the observed heating anomaly, is baroclinic. The atmospheric response to the mid-latitude vorticity forcing is always barotropic, resulting in a geopotential low that is in phase with the forcing. The atmospheric responses to the realistic heat and vorticity forcing show the similar results, suggesting that diabatic heating, transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies. 相似文献
2.
冷暖事件对大气能量循环和纬向平均环流影响的模拟研究 总被引：1，自引：0，他引：1
利用中国科学院大气物理研究所大气科学与地球流体力学数值模拟国家重点实验室新发展的GOALS 5全球海 陆 气耦合模式研究了暖事件 (ElNi no)和冷事件 (LaNina)对大气能量循环和纬向平均环流的影响 ,并用观测资料进行了对比分析。结果表明 :对于纬向平均资料来说 ,冷、暖事件在热带和副热带地区的大气环流相关量的反相变化特征非常清晰 ,中高纬度地区并不明显。此外 ,还发现 ,暖事件时定常涡动的经向热通量的变化是北半球对流层热带外地区温度异常的主要原因 ,而瞬变波的影响则起抵消作用。冷事件时定常波和瞬变波相互抵消的局地特征也依然存在 ,但瞬变波的影响有所增强。 相似文献
3.
亚——非季风区非绝热加热与夏季环流关系的诊断研究 总被引：4，自引：0，他引：4
基于热力适应理论,本文利用 ＮＣＥＰ／ ＮＣＡＲ再分析资料对撒哈拉沙漠、青藏高原和孟加拉湾地区的非绝热加热与夏季环流进行了诊断研究。在非洲撒哈拉沙漠地区,以感热输送为主的加热仅局限于近地面层,边界层以上的大气则以辐射冷却占优势。因而除了边界层内存在着浅薄的正涡度和微弱的上升运动以外,整个对流层几乎都维持负涡度并盛行下沉运动。对于青藏高原地区,强大的表面感热通量引起的垂直扩散是近地面大气加热的主要分量,与大尺度上升运动相关的凝结潜热对低层大气的加热也有一定的贡献。长波辐射造成的对流层中、上层大气的冷却则主要由深对流潜热释放来补偿。夏季高原地区总非绝热加热是正值,且最大加热率出现在边界层内。低空大气辐合产生正涡度,而中、高层大气辐散伴有较强的负涡度。因而高原盛行上升运动,最大上升运动位于近地面层。夏季孟加拉湾地区的深对流凝结潜热释放远大于长波辐的冷却作用,因而整个对流层几乎都保持较强的非绝热加热。４００ｈＰａ层附近的最大加热率引起３００－４００ｈＰａ最强的上升运动。对流层上层是负涡度区,而中、低层为正涡度区。结果还表明,垂直和水平辐散环流与大气的热源和热汇区密切相联：在高层,辐散气流从热源区流向热汇区;在低层则相 相似文献
4.
The Northern Hemisphere winter (DJF) stationary eddy response of a general circulation model (GCM) to a doubling of atmospheric CO2 is simulated with a linear steady state model as a response to anomalies in diabatic heating (latent, sensible and radiative), mountain and transient eddy effects. For this analysis the doubled CO2 experiment performed by Wilson and Mitchell (1987) is used. The linear simulations of the control and perturbation climate capture most of the important features of the GCMs stationary eddies. The simulation of the anomalous stationary eddy pattern in the Northern Hemisphere captures only some of the important features of the GCMs anomalies. The climate anomalies in the Southern Hemisphere are poorly simulated. In the Northern Hemisphere the climate anomalies are dominated by the effect of transient eddies and mountains. In low latitudes also the contribution of latent heating is important. The contributions of sensible and radiative heating are small. 相似文献
5.
The Community Atmosphere Model version 3 (CAM3) temperature simulation bias is examined in this paper. We compare CAM3 output with European Centre for Medium-Range Weather Forecasts (ECMWF) 40 year reanalysis (ERA-40) data. We formulate a time mean temperature bias equation then evaluate each term in the equation. Our focus is on the Northern Hemisphere winter time. We group the temperature equation terms into these categories: linear advection terms, nonlinear advection terms, transient eddy terms and diabatic heating, and find that linear advection and diabatic bias are the largest. The nonlinear terms (velocity bias advection of temperature bias) are much smaller than each of the other groups of terms at all levels except near the surface. Linear advection terms have dipolar pattern in the Atlantic (negative NW of positive) which reflects the shift of the CAM3 model North Atlantic storm track (NAST) into Europe, especially in the upper troposphere; opposite sign dipolar structure occurs over Alaska (positive) and the north Pacific storm track (negative). The transient advection terms in middle latitudes are larger in the upper troposphere and generally positive along the Atlantic storm track. Along the north Pacific storm track (NPST), the transient terms are negative in the mid and lower troposphere over much of the NPST (positive in upper troposphere). The diabatic heating bias has large values in the tropics along the Intertropical Convergence Zone (ICZ) and along the midlatitude storm tracks. During this time of year the ICZ is mainly in the Southern Hemisphere, but CAM3 emphasizes an ICZ-like heating in the northern hemisphere of the Atlantic and Pacific Oceans. CAM3 tends to have a weaker ICZ, especially in the Atlantic. In midlatitudes, we find large bias in heating by precipitation and vertically averaged net radiation over the NAST, Europe, and the Middle East. 相似文献
6.
Changes in storm tracks and energy transports in a warmer climate simulated by the GFDL CM2.1 model 总被引：1，自引：0，他引：1
Yutian Wu Mingfang Ting Richard Seager Huei-Ping Huang Mark A. Cane 《Climate Dynamics》2011,37(1-2):53-72
Storm tracks play a major role in regulating the precipitation and hydrological cycle in midlatitudes. The changes in the location and amplitude of the storm tracks in response to global warming will have significant impacts on the poleward transport of heat, momentum and moisture and on the hydrological cycle. Recent studies have indicated a poleward shift of the storm tracks and the midlatitude precipitation zone in the warming world that will lead to subtropical drying and higher latitude moistening. This study agrees with this key feature for not only the annual mean but also different seasons and for the zonal mean as well as horizontal structures based on the analysis of Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 model simulations. Further analyses show that the meridional sensible and latent heat fluxes associated with the storm tracks shift poleward and intensify in both boreal summer and winter in the late twenty-first century (years 2081?C2100) relative to the latter half of the twentieth century (years 1961?C2000). The maximum dry Eady growth rate is examined to determine the effect of global warming on the time mean state and associated available potential energy for transient growth. The trend in maximum Eady growth rate is generally consistent with the poleward shift and intensification of the storm tracks in the middle latitudes of both hemispheres in both seasons. However, in the lower troposphere in northern winter, increased meridional eddy transfer within the storm tracks is more associated with increased eddy velocity, stronger correlation between eddy velocity and eddy moist static energy, and longer eddy length scale. The changing characteristics of baroclinic instability are, therefore, needed to explain the storm track response as climate warms. Diagnosis of the latitude-by-latitude energy budget for the current and future climate demonstrates how the coupling between radiative and surface heat fluxes and eddy heat and moisture transport influences the midlatitude storm track response to global warming. Through radiative forcing by increased atmospheric carbon dioxide and water vapor, more energy is gained within the tropics and subtropics, while in the middle and high latitudes energy is reduced through increased outgoing terrestrial radiation in the Northern Hemisphere and increased ocean heat uptake in the Southern Hemisphere. This enhanced energy imbalance in the future climate requires larger atmospheric energy transports in the midlatitudes which are partially accomplished by intensified storm tracks. Finally a sequence of cause and effect for the storm track response in the warming world is proposed that combines energy budget constraints with baroclinic instability theory. 相似文献
7.
Utilizing data from NCEP/ NCAR reanalysis, the summertime atmospheric diabatic heating due to different physical processes
is investigated over the Sahara desert, the Tibetan Plateau, and the Bay of Bengal. Atmospheric circulation systems in summer
over these three areas are also studied. Thermal adaptation theory is employed to explain the relationship between the circulation
and the atmospheric diabatic heating.
Over the Sahara desert, heating resulting from the surface sensible heat flux dominates the near-surface layer, while radiative
cooling is dominant upward from the boundary layer. There is positive vorticity in the shallow boundary layer and negative
vorticity in the middle and upper troposphere. Downward motion prevails over the Sahara desert, except in the shallow near—surface
layer where weak ascent exists in summer. Over the Tibetan Plateau, strong vertical diffusion resulting from intense surface
sensible heat flux to the overlying atmosphere contributes most to the boundary layer heating, condensation associated with
large—scale ascent is another contributor to the lower layer heating. Latent heat release accompanying deep convection is
critical in offsetting longwave radiative cooling in the middle and upper troposphere. The overall diabatic heating is positive
in the whole troposphere in summer, with the most intense heating located in the boundary layer. Convergence and positive
vorticity occur in the shallow near—surface layer and divergence and negative vorticity exist deeply in the middle and upper
troposphere. Accordingly, upward motion prevails over the Plateau in summer, with the most intense rising occurring near the
ground surface. Over the Bay of Bengal, summertime latent heat release associated with deep convection exceeds longwave radiative
cooling, resulting in intense heating in almost the whole troposphere. The strongest heating over the Bay of Bengal is located
around 400 hPa, resulting in the most intense rising occurring between 300 hPa and 400 hPa, and producing positive vorticity
in the lower troposphere and negative vorticity in the upper troposphere. It is also shown that the divergent circulation
is from a heat source region to a sink region in the upper troposphere and vice versa in lower layers.
This work was jointly supported by “ National Key Program for Developing Basic Sciences” G1998040904 by NSFC projects 49805003,
49635170, 49823002, and 49825504. 相似文献
8.
This study examines the PNA associated atmospheric diabatic heating by linearly isolating the influence of ENSO. The analysis
is based on the NCEP–NCAR and ERA-40 reanalyses and a 1,000-year-long integration of the CCCma coupled climate model. Both
the vertically integrated and three-dimensional diabatic heating are examined. The Rossby wave sources in association with
the PNA are also diagnosed. The PNA-related heating is confined outside the tropics and is dominated by anomalies in the eastern
Pacific, with a north–south dipole structure in mid-latitudes and the northern subtropics. The heating anomalies change sign
with height in mid-latitudes but have the same sign throughout the troposphere in the northern subtropics. Relatively weak
heating anomalies also appear in mid-latitudes, downstream of the heating dipole over North America and the western North
Atlantic. The heating anomalies are largely supported by the advections related to the mean state throughout the troposphere,
and partially damped by the advections related to the eddy effect, particularly at the upper troposphere over the North Pacific.
Broadly similar patterns are seen from the NCEP–NCAR and ERA-40 reanalyses. Yet anomalous heating centers are generally located
at relatively lower troposphere for the ERA-40 with respect to the NCEP–NCAR. The tropical heating anomalies are rather weak,
remarkably different from those related to ENSO variability. In addition, the Rossby wave source collocates with the atmospheric
diabatic forcing in the mid-high latitudes over the PNA sector, and shows no forcing source in the tropics. The results demonstrate
possible forcing in the mid-high latitudes, regardless of tropical heating for the PNA teleconnection. The modeled heating
and wave forcing anomalies in association with the modeled PNA compare reasonably well with the reanalysis-based estimates,
increasing confidence in the observational results. The analysis provides further evidence of the independence of the PNA
on ENSO from the diabatic heating point of view. 相似文献
9.
《气象科学》2014,(2)
Based on diagnostic analysis of reanalysis data for 58-year,the distribution characteristics of decadal variability in diabatic heating,transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature(SST)anomalies over the North Pacific,as well as their relationship with anomalous atmospheric circulation have been investigated in this paper.A linear baroclinic model(LBM)was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies,and then to compare relative roles of different kinds of forcing in terms of geopotential height responses.The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic.The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow,as well as to the vertical profile of heating.The response to the idealized deep heating over the eastern North Pacific,mimicking the observed heating anomaly,is baroclinic.The atmospheric response to the mid-latitude vorticity forcing is always barotropic,resulting in a geopotential low that is in phase with the forcing.The atmospheric responses to the realistic heat and vorticity forcing show the similar results,suggesting that diabatic heating,transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies. 相似文献
10.
11.
The Diabatic Heating and the Generation of Available Potential Energy: Results from NCEP Reanalysis 总被引：1，自引：0，他引：1
In the existing studies on the atmospheric energy cycle, the attention to the generation of available potential energy (APE) is restricted to its global mean value. The geographical distributions of the generation of APE and its mechanism of formation are investigated by using the three-dimensional NCEP/NCAR diabatic heating reanalysis in this study. The results show that the contributions from sensible heating and net radiation to the generation of zonal and time-mean APE (Gz) are mainly located in high and middle latitudes with an opposite sign, while the latent heating shows a dominant effect on Gz mainly in the tropics and high latitudes where the contributions from the middle and upper tropospheres are also contrary to that from the low troposphere. In high latitudes, the Gz is much stronger for the Winter Hemisphere than for the Summer Hemisphere, and this is consistent with the asymmetrical feature shown by the reservoir- of zonal and time-mean APE in two hemispheres, which suggests that the generation of APE plays a fundamental role in maintaining the APE in the global atmospheric energy cycle. The same contributions to the generation of stationary eddy APE (GSE) from the different regions related to the maintenance of longitudinal temperature contrast are likely arisen by different physics. Specifically, the positive contributions to GSE from the latent heating in the western tropical Pacific and from the sensible heating over land are dominated by the heating at warm regions, whereas those from the latent heating in the eastern tropical Pacific and from the sensitive heating over the oceans are dominated by the cooling at cold regions. Thus, our findings provide an observational estimate of the generation of eddy APE to identify the regional contributions in the climate simulations because it might be correct for the wrong reasons in the general circulation model (GCM). The largest positive contributions to the generation of transient eddy APE (GTE) are found to be at middle latitudes in the middle and upper tropospheres, where reside the strong local contributions to the baroclinic conversion from transient eddy APE to transient eddy kinetic energy and the resulting transient eddy kinetic energy. 相似文献
12.
本文应用谱方法,诊断、计算了1964—1985年间,6个厄尔尼诺年和6个反厄尔尼诺年北半球月、季大气非绝热热流量距平场。结果表明:厄尔尼诺现象对大气非绝热热流量距平场具有显著影响,大气的响应表现为低纬和中高纬非绝热热流量正负距平中心有组织的优势排列,其位相或强度存在低频振荡,并且差值中心表现为双月周期。反厄尔尼诺年,大气具有分布不变,但距平中心基本上为反位相的响应形式。最后,通过海气相关分析,指出了海温异常是决定大气非绝热热流量异常的最重要的原因。 相似文献
13.
利用逐日NCEP/NCAR再分析资料分析了春夏过渡季节青减高原非绝热加热和大气环流季节变化以及亚洲季风爆发的关系.结果表明,过渡季节的早期(5月中旬以前)青藏高原总非绝热加热与感热加热的时间演变曲线趋势一致,感热加热在过渡季节早期的环流演变中有很重要的作用.青藏高原非绝热加热的时间演变与北半球环流的季节变化和亚洲夏季风爆发有很好的相关.在过渡季节里,青藏高原非绝热加热的变化引起了海-陆热力差异对比的变化,给亚洲夏季风的爆发建立了有利的背景环境,对亚洲夏季风爆发有明显的影响.结果还表明,用各区域纬向风垂直差异的时空分布能更准确地表示季节变化的区域差异. 相似文献
14.
本文利用约束变分客观分析法构建的物理协调大气变分客观分析模型,通过融合地面、探空、卫星等多源观测资料和ERA-Interim再分析资料,建立了青藏高原那曲试验区5年（2013～2017年）长时间序列的热力、动力相协调的大气分析数据集,并以此分析那曲试验区大气的基本环境特征与云—降水演变和大气动力、热力的垂直结构。分析表明:（1）试验区350 hPa以上风速的季节变化非常明显,风速在冬季11月至次年2月达到最大（＞50 m s?1）,盛夏7～8月风速的垂直变化最弱,温度的垂直变化最强,大气高湿区在夏秋雨季位于350～550 hPa,在冬春干季升至300～400 hPa。（2）试验区6～7月上旬降水最多;春、秋、冬三季,300～400 hPa高度层作为大气上升运动和下沉运动的交界处,是云量的集中区;夏季,增多的水汽和增强的大气上升运动导致高云和总云量明显增多,中、低云减少。（3）夏季的地表潜热通量与大气总的潜热释放最强,大气净辐射冷却最弱,高原地区较强的地面感热导致试验区500 hPa以下的近地面全年存在暖平流,500 hPa以上则由于强烈的西风和辐射冷却存在冷平流。此外,试验区整层大气全年以干平流为主,但在夏季出现了较弱的湿平流。（4）视热源Q1具有明显的垂直分层特征:全年500 hPa以下大气表现为冷源,300～500 hPa和100～150 hPa表现为热源,150～300 hPa则在冬春干季表现为冷源,在夏秋雨季表现为热源,不同高度层的冷、热源的形成原因不同,其中夏季由于增强的上升运动、感热垂直输送和水汽凝结潜热以及高云的形成,因此几乎整层大气表现为热源。 相似文献
15.
七月中、低纬地区定常波动和加热场的模拟特征 总被引：1，自引：0，他引：1
本文利用P-σ混合坐标原始分程球带模式的最新版本,对七月中、低纬地区的定常波动及非绝热加热场进行了数值模拟。结果表明,模式成功地模拟出了北半球夏季对流层中波数为2的定常波动。高层波峰出现在大陆,波谷出现在海洋上,低层则相反。南半球的副热带高压带也模拟出来了。降水量的模拟也是成功的,特别是位于ITCZ中的积云对流性降水。加热场的模拟结果指出,七月份的热源区除了主要分布在北半球的几个主要大陆上,还分布在热带海洋上ITCZ所在区;其余的广大洋面则显示出冷源的性质。其中热带海洋的热源以潜热加热为主(主要分布于大气的中高层),大陆上的热源有的以感热为主(主要分布于大气的低层),有的仍以潜热加热贡献较大。海洋的冷源是由长波辐射冷却造成的。 相似文献
16.
500hPa月平均高度相关的地理分布及其季节变化 总被引：1，自引：0，他引：1
本文分析了北半球３４年月平均５００ｈＰａ高度异常的月－月相关特征。结果表明，北半球高度异常的总体相关是大于零的，在副热带相关系数可达０．３以上，在中高纬度约为０．０－０．２，亚洲和北美地区中高纬的环流异常相关还显示出明显的季节变化特征，在冬夏季有最强的相关，春秋季相关最弱。 相似文献
17.
基于1979—2021年的ERA5再分析资料,研究了副极地海洋锋区(Subarctic Frontal Zone, SAFZ)海温(Sea Surface Temperature, SST)异常相关的冬季海气相互作用过程及其影响次年冬季厄尔尼诺(El Niño)的机制。研究表明,冬季SAFZ的特征海气异常表现为大尺度的SST暖异常与偶极型的大气环流异常。在SAFZ海气相互作用过程中,海洋首先通过直接的非绝热加热影响低层大气斜压性,随后通过间接的瞬变涡旋反馈使相当正压的位势高度异常在整个冬季内维持。其中,南部的气旋式环流异常通过减弱副热带的平均信风激发太平洋经向模态(Pacific Meridional Mode, PMM)与风—蒸发—SST (Wind-Evaporation-SST, WES)反馈,从而使中纬度SST暖异常南传至热带太平洋中部,随后导致El Niño发生。然而,并非所有的SAFZ暖异常事件都能激发次年冬季的El Niño,中纬度海气耦合异常的初始配置及同期热带太平洋的表现情况将对中纬度信号南传至热带的过程产生较大的影响。 相似文献
18.
夏季青藏高原加热和北半球环流年际变化的相关分析 总被引：16，自引：5，他引：16
利用 195 8～ 1997年NCEP/NCAR再分析数据集中加热率和环流资料 ,采用相关分析和对比分析相结合的方法 ,诊断和分析了夏季青藏高原的非绝热加热与北半球环流系统的年际变化的联系。分析结果表明 :夏季青藏高原的加热强 (弱 )的年份 ,高原及邻近地区的上升运动、下层辐合及上层辐散均增强 (减弱 ) ,使高原加热对周边地区低层暖湿空气的抽吸效应和对高层大气向周边地区的排放作用加强 (减弱 )。从而影响着高原和周边地区的环流以及亚洲季风区大尺度环流系统。而且高原的加热强迫能够激发产生一支沿亚欧大陆东部海岸向东北方向传播的Rossby波列 ,其频散效应可影响到更远的东太平洋以至北美地区的大气环流 相似文献
19.
In a general baroclinic atmosphere,when the basic state includes meridional circulation,the sta-tionary waves might not only pass through the equatorial easterlies,but also strengthen significantly.The orographic forcing in the Northern Hemisphere mid-latitude might cause marked responses in thelow latitude atmosphere.This suggests that the meridional circulation plays an important role in theconnection of stationary responses in mid and low latitudes,and so does the heating forcing in theNorthern Hemisphere mid-latitude.Forced by the heating forcing in the Northern Hemisphere mid-latitude,the features similar to the Northern Hemisphere summer monsoon circulation can be ob-tained.It appears that the meridional circulation plays certain role in the formation of summer mon-soon circulation.The heating anomaly forcing located at the eastern equatorial Pacific makes the sta-tionary waves present PNA(Pacific-North America)pattern in the winter hemisphere,but it doesnot in the summer hemisphere.It suggests that the meridional circulation has a marked influence onthe route of stationary wave propagation both in the winter and summer hemispheres. 相似文献
20.
南亚高压的季节变化与趋暖性 总被引：27，自引：3，他引：27
利用NCEP／NCAR再分析资料，分析了南亚高压的季节变化，讨论了对流层中高层温度、整层大气视热源和非绝热加热率的时空变化对南亚高压季节变化的影响。结果表明，南亚高压存在两个季节平衡态，即夏半年的大陆高压和冬半年的海洋高压，大陆高压又可分为青藏高压和伊郎高压。加热场对南亚高压的季节变化有重要作用，南亚高压是一个暖性高压，其中心有“趋热性”，通常位于或趋于加热率的相对大值区。南亚高压的年循环过程，主要受南亚地区潜热和感热季节变化的支配。夏季北方地区和高压地区的强烈短波辐射加热对高压中心北移和维持也有作用，长波辐射的冷却作用则是高压减弱的重要原因。 相似文献