共查询到19条相似文献，搜索用时 125 毫秒
1.
对大气环流模式PIAP3进行了30 a季节运行, 对其物理过程的温度调整倾向进行了系统分析, 研究发现:大气总辐射效应以冷却为主, 长波辐射温度倾向与温度本身具有负反馈关系, 与云量有正反馈关系。太阳短波辐射加热倾向直接反映了太阳直射点冬夏的季节转换;深厚对流和大尺度降水, 作为大气的重要加热机制, 是辐射冷却的重要平衡因子, 两者地域互补, 前者加热热带深厚大气, 后者主要加热中高纬对流层中低层大气。干、湿对流是低层大气热力混合的有效机制, 分别完成北半球中高纬和热带地区的低层热力混合, 两者共同作用消除不稳定。垂直涡旋扩散与浅积云对流对低层大气形成热量传输的互补匹配, 两者分别实现陆面和海面低层大气热量的有效传输混合, 并共同构成下垫面边界层和自由大气间的有效垂直传输机制。浅对流活跃区处于强盛深厚对流区的下游方向, 大尺度层结降水有利于浅积云的发展。物理过程净温度调整是各过程调整平衡的结果, 除赤道南北两侧的热带地区存在两个深厚的温度调整柱外, 边界层以上的整个对流层主体均以降温为主, 而边界层以下则以加热为主。 相似文献
2.
中国及邻近地区污染排放对对流层臭氧变化与辐射影响的研究 总被引：11，自引：1，他引：10
利用双向耦合的区域气候模式和大气化学模式系统, 研究了中国与邻近地区人为污染排放引起对流层臭氧变化和产生的辐射强迫.结果表明, 污染排放对对流层臭氧含量的影响有明显的季节变化, 对北方的影响不如南方显著, 西部的季节变化稳定且小于东部, 内陆污染地区各季节臭氧柱含量的变化量均较高.对整个模拟区域而言, 臭氧变化量的年平均值为30.928 DU, 春季最大为32.168 DU, 而空间分布变化在12～38 DU之间.臭氧变化量对北方地区辐射的影响较小, 而对低纬和华东地区影响较大, 臭氧变化量引起的晴空地气系统短波辐射强迫、长波辐射强迫的平均值分别是0.185 W·m-2和0.464 W·m-2, 标准化短波辐射强迫与净辐射强迫值为0.006 W·m-2·DU-1和0.021 W·m-2·DU-1.气候反馈过程对对流层臭氧含量的影响范围在-0.470～0.752 DU之间, 包含气候反馈过程的区域年平均臭氧变化量是30.942 DU.在气候反馈条件下, 臭氧变化量的短波和长波辐射强迫分别是0.249 W·m-2及 0.482 W·m-2, 标准化的短波与净辐射强迫值为0.008 W·m-2·DU-1和0.024 W·m-2·DU-1.臭氧变化量导致地表温度的变化范围在±0.80 K之间. 相似文献
3.
本文采用NCAR气候系统模式CSM1.4研究了冬季风对强外辐射强迫变化的响应,其中外辐射强迫直接由太阳常数的变化而引入。结果表明：随太阳常数的增加,局地的增温幅度变化很大,中高纬地区比低纬地区增暖幅度强,这在太阳常数增加较大的试验中表现更为明显;随太阳常数增大越大,大气温度升高越高,对流层有强烈增温,对流层高层尤为显著,平流层中上层有降温现象;随太阳常数增大,亚洲冬季风系统的响应越强,系统强度增强明显,但形式不同,500hPa随纬度增高增强幅度变大,100hPa随纬度增高增强幅度变小。 相似文献
4.
利用2001年11月—2005年10月"云与地球辐射能量系统(CERES)"辐射和云资料SYN(Syn-optic Radiation Fluxes and Clouds),分析了青藏高原(下称高原)地区不同高度云辐射强迫的时空变化特征。结果表明:(1)高原整体为云强迫正、负值的过渡区域,这种过渡性有显著的季节差异和区域划分。高原东南部表现出较强的冷却效应,其西部和东北部干旱区在冬、春季表现为较弱的加热效应。(2)高云、高的中云和低的中云对云短波辐射强迫的季节变化都有贡献,其中中云是导致区域差异的主要因素;云长波辐射强迫的区域差异不明显,但季节差异显著,这主要是由高的中云和高云的变化引起的,且云量是主要的影响因子,高云云量虽小但其影响不可忽视。(3)高云在高原地区产生净加热效应,高的中云既产生加热作用也产生冷却作用,低的中云产生净冷却效应。(4)云短波辐射强迫在云辐射强迫的日变化中仍然占主导地位,日变化的区域差异主要是由云量引起的。白天,在云短波辐射强迫的日变化中,低的中云贡献更大。高云对云长波辐射强迫的日变化贡献主要在晚上,低的中云在夜间对云长波辐射强迫有抑制作用。 相似文献
5.
本文采用NCAR气候系统模式CSM 1.4研究了冬季风对强外辐射强迫变化的响应,其中外辐射强迫直接由太阳常数的变化而引入。结果表明:随太阳常数的增加,局地的增温幅度变化很大,中高纬地区比低纬地区增暖幅度强,这在太阳常数增加较大的试验中表现更为明显;随太阳常数增大越大,大气温度升高越高,对流层有强烈增温,对流层高层尤为显著,平流层中上层有降温现象;随太阳常数增大,亚洲冬季风系统的响应越强,系统强度增强明显,但形式不同,500 hPa随纬度增高增强幅度变大,100 hPa随纬度增高增强幅度变小。 相似文献
6.
利用作者在本文第Ⅰ部分提出的原始方程系统中的无加速定理,这部分讨论大气动量、热量的内外源强迫对纬向平均温度场的作用。数值计算结果表明:外源热力强迫引起的温度场的变化主要在对流层下层;而热力内强迫的作用在中高纬对流层中分布较均匀,两者在维持纬向平均温度场的变化中十分重要。机械外强迫和机械内强迫各自的贡献次之。平均经圈环流的贡献则主要在对流层顶附近及平流层中,由于热力内强迫产生的位温变化在一定程度上大致被热力外强迫所平衡,而机械内、外强迫则具有相似的空间分布,从而,总的热力强迫所引起的位温变化的分布基本上为总的机械强迫作用所平衡,纬向平均位温的准定常状态由此得以维持。 相似文献
7.
原始方程系统中的无加速定理——Ⅱ:纬向平均温度的变化 总被引：1，自引：0，他引：1
利用作者在本文第Ⅰ部分提出的原始方程系统中的无加速定理,这部分讨论大气动量、热量的内外源强迫对纬向平均温度场的作用。数值计算结果表明:外源热力强迫引起的温度场的变化主要在对流层下层;而热力内强迫的作用在中高纬对流层中分布较均匀,两者在维持纬向平均温度场的变化中十分重要。机械外强迫和机械内强迫各自的贡献次之。平均经圈环流的贡献则主要在对流层顶附近及平流层中,由于热力内强迫产生的位温变化在一定程度上大致被热力外强迫所平衡,而机械内、外强迫则具有相似的空间分布,从而,总的热力强迫所引起的位温变化的分布基本上为总的机械强迫作用所平衡,纬向平均位温的准定常状态由此得以维持。 相似文献
8.
本文与文献[1]相对应,利用一个非线性初始方程谱模式,研究了中、高纬度理想化的大尺度地形以及北半球实际地形的动力强迫作用对于冬季行星尺度的大气定常波的影响。计算结果证实,根据线性模式的数值试验结果所做的定性分析在非线性情形下仍然是成立的,同时,非线性扰动流场也与线性流场有明显的差异,在纬向平场基本气流相对较弱的地区或垂直层次上差异尤为显著。数值试验表明,北半球实际地形强迫的大尺度扰动,在对流层低层以及对流层上部的中、高纬均主要表现出纬向波数为2的行星波,但是在对流层上部的低纬地区3波分量比较明显。中、高纬的大地形动力强迫作用,对于低纬太平洋高空的反气旋和气旋环流的形成有重要的贡献。 相似文献
9.
沙尘气溶胶辐射强迫全球分布的模拟研究 总被引：7，自引：2，他引：5
为了定景了解沙尘气溶胶对气候的影响,文中利用一个改进的辐射传输模式,结合伞球气溶胶数据集(G-ADS),计算了晴空条件下,冬夏两季沙尘气溶胶的直接辐射强迫在对流层顶和地面的全球分布,并讨论了云对沙尘气溶胶辐射强迫的影响.计算结果表明,对北半球冬季和夏季而言,在对流层顶沙尘气溶胶的全球短波辐射强迫的平均值分别为-0.477和-0.501 W/m2;长波辐射强迫分别为0.11和0.085 W/m2;全球平均短波地面辐射强迫冬夏两季分别为-1.362和-1.559 W/m2;长波辐射强迫分别为0.274和0.23 W/m2.沙尘气溶胶在对流层顶和地面的负辐射强迫的绝对值郁随太阳天顶角的余弦和地表反照率的增加而增大;地表反照率对沙尘气溶胶辐射强迫的强度和分布都有重要影响.研究指出:云对沙尘气溶胶的直接辐射强迫的影响不仅取决于云量,而且取决于云的高度和云水路径,以及地面反照率和太阳高度角等综合因素.中云和低云对沙尘气溶胶在对流层顶的短波辐射强迫的影响比高云明显.云的存在都使对流层顶长波辐射强迫减少,其中低云的影响最为明显.因此,在估算沙尘气溶胶总的直接辐射强迫时,云的贡献不可忽视. 相似文献
10.
夏季我国干旱、半干旱区陆面过程能量平衡及其局地大气环流 总被引：28，自引：10，他引：18
利用NCEP资料分析得出,夏季我国干旱,半干旱区在整个欧亚大陆上是陆面感热通量最强的地方,与此对应的陆面潜热通量则最弱.陆面所接收的太阳短波辐射主要以感热和长波辐射的能量形式释放.该区降水量很少,降水量的年际变率也很弱;因此,该区的陆面热量通量都显出很弱的年际变率;然而,这些通量的年代际变率信号则比较显著.我国干旱、半干旱区大气环流的热力过程与其陆面过程特征密切相关.该区对流层大气的辐射冷却很强,达-3 K d-1.由于缺乏水汽和上升运动,大尺度凝结加热率、深对流加热率、浅对流加热率都非常弱.因此,600hPa以上的大气以绝热下沉加热来平衡辐射冷却;600hPa以下,陆面感热引起的垂直扩散加热率非常强,多达8 K d-1,它除了平衡辐射冷却以外还制造对流层低层的对流运动,以绝热上升冷却来平衡多余的垂直扩散加热.总之,我国干旱、半干旱区的陆面过程特征决定了该区大气运动的特殊垂直结构,即对流层低层对流上升运动及其上层的下沉运动.我国干旱、半干旱区陆面能量平衡及其局地大气环流的年代际变率,是全球气候系统年代际变率的必然结果. 相似文献
11.
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
12.
WINTERTIME MIDDLE EAST SUBTROPICAL WESTERLY JET STREAM INTERANNUAL VARIATION CHARACTERISTICS AND ITS POSSIBLE PHYSICAL FACTORS 总被引：1，自引：0，他引：1
Using National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) monthly reanalysis data and an extended reconstruction of the sea surface temperature data provided by National Oceanic and Atmospheric Administration, the basic characteristics of the interannual variation in the wintertime Middle East subtropical westerly jet stream (MEJ) and its possible physical factors are studied. The results show that the climatological mean MEJ axis extends southwestward-northeastward and that its center lies in the northwest part of the Arabian Peninsula. The south-north shift of the MEJ axis and its intensity show obvious interannual variations that are closely related to the El Ni?o-Southern Oscillation (ENSO) and the mid-high latitude atmospheric circulation. The zonal symmetric response of the Asian jet to the ENSO-related tropical convective forcing causes the MEJ axis shift, and the Arctic Oscillation (AO) causes the middle-western MEJ axis shift. Due to the influences of both the zonal symmetric response of the Asian jet to the ENSO-related tropical convective forcing and the dynamical role of the AO, an east-west out-of-phase MEJ axis shift is observed. Furthermore, the zonal asymmetric response to the ENSO-related tropical convective forcing can lead to an anomalous Mediterranean convergence (MC) in the high troposphere. The MC anomaly excites a zonal wave train along the Afro-Asian jet, which causes the middle-western MEJ axis shift. Under the effects of both the zonal symmetric response to the ENSO-related tropical convective forcing and the wave train along the Afro-Asian jet excited by the MC anomaly, an east-west in-phase MEJ axis shift pattern is expressed. Finally, the AO affects the MEJ intensity, whereas the East Atlantic (EA) teleconnection influences the middle-western MEJ intensity. Under the dynamical roles of the AO and EA, the change in the MEJ intensity is demonstrated. 相似文献
13.
A set of numerical experiments designed to analyze the oceanic forcing in spring show that the combined forcing of cold （warm） El Ni（n）o （La Ni（n）a） phases in the Ni（n）o4 region and sea surface temperature anomalies （SSTA） in the westerly drifts region would result in abnormally enhanced NorthEast Cold Vortex （NECV） activities in early summer.In spring,the central equatorial Pacific El Ni（n）o phase and westerly drift SSTA forcing would lead to the retreat of non-adiabatic waves,inducing elliptic low-frequency anomalies of tropical air flows.This would enhance the anomalous cyclone-anticyclonecyclone-anticyclone low-frequency wave train that propagates from the tropics to the extratropics and further to the mid-high latitudes,constituting a major physical mechanism that contributes to the early summer circulation anomalies in the subtropics and in the North Pacific mid-high latitudes.The central equatorial Pacific La Ni（n）a forcing in the spring would,on the one hand,induce teleconnection anomalies of high pressure from the Sea of Okhotsk to the Sea of Japan in early summer,and on the other hand indirectly trigger a positive low-frequency East Asia-Pacific teleconnection （EAP） wave train in the lower troposphere. 相似文献
14.
In this study, a coupled atmosphere-surface “climate feedback-response analysis method” (CFRAM) was applied to the slab ocean model version of the NCAR CCSM3.0 to understand the tropospheric warming due to a doubling of CO2 concentration through quantifying the contributions of each climate feedback process. It is shown that the tropospheric warming displays distinct meridional and vertical patterns that are in a good agreement with the multi-model mean projection from the IPCC AR4. In the tropics, the warming in the upper troposphere is stronger than in the lower troposphere, leading to a decrease in temperature lapse rate, whereas in high latitudes the opposite it true. In terms of meridional contrast, the lower tropospheric warming in the tropics is weaker than that in high latitudes, resulting in a weakened meridional temperature gradient. In the upper troposphere the meridional temperature gradient is enhanced due to much stronger warming in the tropics than in high latitudes. Using the CFRAM method, we analyzed both radiative feedbacks, which have been emphasized in previous climate feedback analysis, and non-radiative feedbacks. It is shown that non-radiative (radiative) feedbacks are the major contributors to the temperature lapse rate decrease (increase) in the tropical (polar) region. Atmospheric convection is the leading contributor to temperature lapse rate decrease in the tropics. The cloud feedback also has non-negligible contributions. In the polar region, water vapor feedback is the main contributor to the temperature lapse rate increase, followed by albedo feedback and CO2 forcing. The decrease of meridional temperature gradient in the lower troposphere is mainly due to strong cooling from convection and cloud feedback in the tropics and the strong warming from albedo feedback in the polar region. The strengthening of meridional temperature gradient in the upper troposphere can be attributed to the warming associated with convection and cloud feedback in the tropics. Since convection is the leading contributor to the warming differences between tropical lower and upper troposphere, and between the tropical and polar regions, this study indicates that tropical convection plays a critical role in determining the climate sensitivity. In addition, the CFRAM analysis shows that convective process and water vapor feedback are the two major contributors to the tropical upper troposphere temperature change, indicating that the excessive upper tropospheric warming in the IPCC AR4 models may be due to overestimated warming from convective process or underestimated cooling due to water vapor feedback. 相似文献
15.
20世纪90年代末东亚冬季风年代际变化特征及其内动力成因 总被引：10，自引：4，他引：6
为纪念陶诗言先生对东亚冬季风研究的杰出贡献,本文利用我国测站、NCEP/NCAR和ERA-40/ERA-Interim再分析资料分析了我国冬季气温和东亚冬季风在20世纪90年代末所发生的年代际跃变特征及其内动力成因。分析结果表明:从20世纪90年代末之后,我国冬季气温和东亚冬季风发生了明显的年代际跃变。从1999年之后,随着东亚冬季风从偏弱变偏强,我国冬季气温变化从全国一致变化型变成南北振荡型（即北冷南暖型）,并由于从1999年之后我国北方冬季气温从偏高变成偏低,故冬季低温雪暴冰冻灾害频繁发生,同时,我国冬季气温和东亚冬季风年际变化在此时期从以往3～4 a周期年际变化变成2～8 a周期;并且,结果还表明了东亚冬季风此次年代际变化是由于西伯利亚高压和阿留申低压的加强所致。本文还从北极涛动（AO）和北半球准定常行星波活动的动力理论进一步讨论了此次东亚冬季风年代际跃变的内动力成因及其机理,结果表明:从20世纪90年代末之后,北半球冬季准定常行星波在高纬地区沿极地波导传播到平流层加强,而沿低纬波导传播到副热带对流层上层减弱,这造成了行星波E-P通量在高纬度地区对流层和平流层辐合加强,而在副热带地区对流层中、上层辐散加强,因而导致了北半球高纬度地区从对流层到平流层纬向平均纬向流和欧亚上空极锋急流减弱,而副热带急流加强,这造成了AO减弱和东亚冬季风加强。 相似文献
16.
近50 a北半球和青藏高原地面及其高空温度变化的初步分析 总被引：6，自引：1，他引：5
通过分析北半球和青藏高原地面平均气温与它们上空500hPa平均温度、200一500hPa平均厚度在不同时期和不同纬度带的趋势变化特征,了解其地面气温和其对流层中上层温度的年代际变化趋势以及相互关系。可以看到近50a地面气温和500hPa温度年代际变化大致相同,20世纪70年代中期之前都为降温,70年代中期以后为不同程度的升温。200—500hPa厚度代表的对流层上层温度与对流层下层温度变化趋势相反,70年代前明显升温,70年代后明显降温。分析还表明,对流层各层温度在不同纬度和不同季节的变化也不同。 相似文献
17.
本文从赤道β平面近似下的线性化扰动方程组出发,基于第二类条件不稳定(CISK)理论,研究了热带对流层大气准40天低频振荡的动力机制。研究发现,当对流层中、上层存在较大的对流凝结加热时可激发出纬向波数为1、周期为40天左右的不稳定Kelvin波,它以每天8到11个经度的相速缓慢向东移动。由此指出,观测到的热带对流层大气30—50天的低频振荡可能正是这种由对流凝结加热所驱动的缓慢东移的Kelvin波的具体表现。这可对热带对流层大气30—50天低频振荡现象的动力机制给以初步的物理解释。 相似文献
18.
基于1979—2014年ERA-Interim逐日再分析温度资料,依据温度递减率插值法计算出青藏高原及同纬度其他地区热带对流层顶气压数据,比较了高原和同纬度其他地区热带对流层顶气压季节变化和长期变化趋势,讨论了热带对流层顶气压与高空温度的关系。结果表明:1)在季节变化上,除12月和1月外,青藏高原热带对流层顶气压全年低于同纬度其他地区;青藏高原热带对流层顶气压、对流层中上层以及平流层下部平均温度均表现出比同纬度其他地区更明显的单峰型特征。2)热带对流层顶气压与高空温度变化关系密切,对流层中上层(平流层下部)平均温度升高(降低),有利于热带对流层顶气压降低;相对于同纬度其他地区,青藏高原对流层顶气压与对流层中上层平均温度的关系更密切。3)1979—2014年青藏高原和同纬度其他地区各季节的热带对流层顶气压均呈现出不同程度的下降趋势,冬春季下降趋势更加显著;青藏高原各季节对流层中上层增温和平流层下部降温的幅度均超过同纬度其他地区,导致其热带对流层顶气压的下降趋势比同纬度其他地区更加明显。 相似文献
19.
Realistic simulation of the internal variability of the climate system is important both for climate change detection and
as an indicator of whether the physics of the climate system is well-represented in a climate model. In this work zonal mean
atmospheric temperatures from a control run of the second Hadley Centre coupled GCM are compared with gridded radiosonde observations
for the past 38 years to examine how well modelled and observed variability agree. On time scales of between six months and
twenty years, simulated and observed variability of global mean temperatures agree well for the troposphere, but in the equatorial
stratosphere variability is lower in the model than in the observations, particularly at periods of two years and seven to
twenty years. We find good agreement between modelled and observed variability in the mass-weighted amplitude of a forcing-response
pattern, as used for climate change detection, but variability in a signal-to-noise optimised fingerprint pattern is significantly
greater in the observations than in a model control run. This discrepancy is marginally consistent with anthropogenic forcing,
but more clearly explained by a combination of solar and volcanic forcing, suggesting these should be considered in future
`vertical detection' studies. When the relationship between tropical lapse rate and mean temperature was examined, it was
found that these quantities are unrealistically coherent in the model at periods above three years. However, there is a clear
negative lapse rate feedback in both model and observations: as the tropical troposphere warms, the mid-tropospheric lapse
rate decreases on all the time scales considered.
Received: 11 August 1998 / Accepted: 20 July 1999 相似文献