共查询到20条相似文献，搜索用时 31 毫秒
1.
Yuyang GUO Yongqiang YU Pengfei LIN Hailong LIU Bian HE Qing BAO Bo AN Shuwen ZHAO Lijuan HUA 《大气科学进展》2020,37(10):1133-1148
This study documents simulated oceanic circulations and sea ice by the coupled climate system model FGOALS-f3-L developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, under historical forcing from phase 6 of the Coupled Model Intercomparison Project (CMIP6). FGOALS-f3-L reproduces the fundamental features of global oceanic circulations, such as sea surface temperature (SST), sea surface salinity (SSS), mixed layer depth (MLD), vertical temperature and salinity, and meridional overturning circulations. There are notable improvements compared with the previous version, FGOALS-s2, such as a reduction in warm SST biases near the western and eastern boundaries of oceans and salty SSS biases in the tropical western Atlantic and eastern boundaries, and a mitigation of deep MLD biases at high latitudes. However, several obvious biases remain. The most significant biases include cold SST biases in the northwestern Pacific (over 4°C), freshwater SSS biases and deep MLD biases in the subtropics, and temperature and salinity biases in deep ocean at high latitudes. The simulated sea ice shows a reasonable distribution but stronger seasonal cycle than observed. The spatial patterns of sea ice are more realistic in FGOALS-f3-L than its previous version because the latitude–longitude grid is replaced with a tripolar grid in the ocean and sea ice model. The most significant biases are the overestimated sea ice and underestimated SSS in the Labrador Sea and Barents Sea, which are related to the shallower MLD and weaker vertical mixing. 相似文献
2.
The present study examines simulated oceanic climatology in the Flexible Global Ocean-Atmosphere-Land System model, Grid-point Version 2 (FGOALS-g2) forced by historical external forcing data. The oceanic temperatures and circulations in FGOALS-g2 were found to be comparable to those observed, and substantially improved compared to those simulated by the previous version, FGOALS-g1.0. Compared with simulations by FGOALS-g1.0, the shallow mixed layer depths were better captured in the eastern Atlantic and Pacific Ocean in FGOALS-g2. In the high latitudes of the Northern Hemisphere, the cold biases of SST were about 1°C–5°C smaller in FGOALS-g2. The associated sea ice distributions and their seasonal cycles were more realistic in FGOALS-g2. The pattern of Atlantic Meridional Overturning Circulation (AMOC) was better simulated in FGOALS-g2, although its magnitude was larger than that found in observed data. The simulated Antarctic Circumpolar Current (ACC) transport was about 140 Sv through the Drake Passage, which is close to that observed. Moreover, Antarctic Intermediate Water (AAIW) was better captured in FGOALS-g2. However, large SST cold biases (>3°C) were still found to exist around major western boundary currents and in the Barents Sea, which can be explained by excessively strong oceanic cold advection and unresolved processes owing to the coarse resolution. In the Indo-Pacific warm pool, the cold biases were partly related to the excessive loss of heat from the ocean. Along the eastern coast in the Atlantic and Pacific Oceans, the warm biases were due to overestimation of shortwave radiation. In the Indian Ocean and Southern Ocean, the surface fresh biases were mainly due to the biases of precipitation. In the tropical Pacific Ocean, the surface fresh biases (>2 psu) were mainly caused by excessive precipitation and oceanic advection. In the Indo-Pacific Ocean, fresh biases were also found to dominate in the upper 1000 m, except in the northeastern Indian Ocean. There were warm and salty biases (3°C–4°C and 1–2 psu) from the surface to the bottom in the Labrador Sea, which might be due to large amounts of heat transport and excessive evaporation, respectively. For vertical structures, the maximal biases of temperature and salinity were found to be located at depths of >600 m in the Arctic Ocean, and their values exceeded 4°C and 2 psu, respectively. 相似文献
3.
Freshwater flux (FWF) directly affects sea surface salinity (SSS) and hence modulates sea surface temperature (SST) in the tropical Pacific. This paper quantifies a positive correlation between FWF and SST using observations and simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to analyze the interannual variability in the tropical Pacific. Comparisons among the displacements of FWF, SSS and SST interannual variabilities illustrate that a large FWF variability is located in the west-central equatorial Pacific, covarying with a large SSS variability, whereas a large SST variability is located in the eastern equatorial Pacific. Most CMIP5 models can reproduce the fact that FWF leads to positive feedback to SST through an SSS anomaly as observed. However, the difference in each model's performance results from different simulation capabilities of the CMIP5 models in the magnitudes and positions of the interannual variabilities, including the mixed layer depth and the buoyancy flux in the equatorial Pacific. SSS anomalies simulated from the CMIP5 multi-model are sensitive to FWF interannual anomalies, which can lead to differences in feedback to interannual SST variabilities. The relationships among the FWF, SSS and SST interannual variabilities can be derived using linear quantitative measures from observations and the CMIP5 multi-model simulations. A 1 mm d-1 FWF anomaly corresponds to an SSS anomaly of nearly 0.12 psu in the western tropical Pacific and a 0.11°C SST anomaly in the eastern tropical Pacific. 相似文献
4.
You-Soon Chang Shaoqing Zhang Anthony Rosati Thomas L. Delworth William F. Stern 《Climate Dynamics》2013,40(3-4):775-803
The Geophysical Fluid Dynamics Laboratory has developed an ensemble coupled data assimilation (ECDA) system based on the fully coupled climate model, CM2.1, in order to provide reanalyzed coupled initial conditions that are balanced with the climate prediction model. Here, we conduct a comprehensive assessment for the oceanic variability from the latest version of the ECDA analyzed for 51 years, 1960–2010. Meridional oceanic heat transport, net ocean surface heat flux, wind stress, sea surface height, top 300 m heat content, tropical temperature, salinity and currents are compared with various in situ observations and reanalyses by employing similar configurations with the assessment of the NCEP’s climate forecast system reanalysis (Xue et al. in Clim Dyn 37(11):2511–2539, 2011). Results show that the ECDA agrees well with observations in both climatology and variability for 51 years. For the simulation of the Tropical Atlantic Ocean and global salinity variability, the ECDA shows a good performance compared to existing reanalyses. The ECDA also shows no significant drift in the deep ocean temperature and salinity. While systematic model biases are mostly corrected with the coupled data assimilation, some biases (e.g., strong trade winds, weak westerly winds and warm SST in the southern oceans, subsurface temperature and salinity biases along the equatorial western Pacific boundary, overestimating the mixed layer depth around the subpolar Atlantic and high-latitude southern oceans in the winter seasons) are not completely eliminated. Mean biases such as strong South Equatorial Current, weak Equatorial Under Current, and weak Atlantic overturning transport are generated during the assimilation procedure, but their variabilities are well simulated. In terms of climate variability, the ECDA provides good simulations of the dominant oceanic signals associated with El Nino and Southern Oscillation, Indian Ocean Dipole, Pacific Decadal Oscillation, and Atlantic Meridional Overturning Circulation during the whole analyzed period, 1960–2010. 相似文献
5.
基于耦合器框架，中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室大气环流谱模式 （SAMIL）最近成功地实现了与海洋、海冰等气候分量模式的耦合，形成了“非通量调整”的海－陆－气－冰直接耦合的气候模式系统（FGOALS-s）。在耦合系统中，由于海温、海冰等的分布由预报模式驱动，大气与海洋、海冰之间引入了相互作用过程，这样大气环流的模拟特征与耦合前会有不同。为分析耦合系统的性能，作者对耦合前后的模拟结果进行了分析比较，重点是大气模拟特征的差异。结果表明，耦合前、后大气环流的基本特征相似，都能成功地模拟出主要的环流系统分布及季节变化，但是由于海温和海冰的模拟存在系统性的偏差，使得耦合后的大气环流受到明显影响。例如耦合后热带海温偏冷，南大洋、北太平洋和北大西洋等中纬度地区的海温偏高，导致海温等值线向高纬海域的伸展较弱，海温经向梯度减小。耦合后海冰在北极区域范围偏大，在南极周边地区则偏小。海温、海冰分布模拟的偏差影响到中、高纬低层大气的温度。热带海温偏低，使得赤道地区降水偏弱，凝结潜热减少，热带对流层中高层温度比耦合前要低，大气温度的经向梯度减小。经向温度梯度的改变，直接影响到对平均经圈环流及西风急流强度的模拟。尽管耦合系统中海温、海冰的模拟存在偏差，但在亚洲季风区，耦合后季风环流及降水等的分布都比耦合前单独大气模式的结果合理，表明通过海[CD*2]气相互作用可减少耦合前季风区的模拟误差，改善季风模拟效果。比较发现，海温、海冰模拟的偏差，除与海洋模式中经向热输送偏弱、海冰模式中海冰处理等有关外，也与大气模式中总云量模拟偏低有关。大气模式本身的误差，特别是云、辐射过程带来的误差，对耦合结果具有极为重要的影响。完全耦合后，这些误差通过与海洋、海冰的反馈作用而放大。因此，对于FGOALS-s而言，要提高耦合系统的整体性能，除改进各气候分量模式的模拟性能外，需要重点改进大气模式中的云、辐射过程。 相似文献
6.
Numerical Simulation of Atmosphere-Ocean-Sea Ice Interaction During Interannual Cycle in High Northern Latitudes 总被引：1，自引：0，他引：1 
下载免费PDF全文
下载免费PDF全文 LIU Xiying LIU Hailong LI Wei ZHANG Xuehong YU Rucong YU Yongqiang 《Acta Meteorologica Sinica》2008,22(1):119-128
The interannual atmosphere-ocean-sea ice interaction （AOSI） in high northern latitudes is studied with a global atmosphere-ocean-sea ice coupled model system, in which the model components of atmosphere and land surface are from China National Climate Center and that of ocean and sea ice are from LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences. A daily flux anomaly correction scheme is employed to couple the atmosphere model and the ocean model with the effect of inhomogenity of sea ice in high latitudes is considered. The coupled model system has been run for 50 yr and the results of the last 30 years are analyzed. After the sea level pressure （SLP）, surface air temperature （SAT）, sea surface temperature （SST）, sea ice concentration （SIC）, and sea surface sensible heat flux （SHF） are filtered with a digital filter firstly, their normalized anomalies are used to perform the decomposition of combined complex empirical orthogonal function （CCEOF） and then they are reconstructed with the leading mode. The atmosphere-ocean-sea ice interactions in high northern latitudes during a periodical cycle （approximately 4 yr） are analyzed. It is shown that： （1） When the North Atlantic Oscillation （NAO） is in its positive phase, the southerly anomaly appears in the Greenland Sea, SAT increases, the sea loses less SHF, SST increases and SIC decreases accordingly; when the NAO is in its negative phase, the northerly anomaly appears in the Greenland Sea, SAT decreases, the sea loses more SHF, SST decreases and SIC increases accordingly. There are similar features in the Barents Sea, but the phase of evolution in the Barents Sea is different from that in the Greenland Sea. （2） For an average of multi-years, there is a cold center in the inner part of the Arctic Ocean near the North Pole. When there is an anomaly of low pressure, which is closer to the Pacific Ocean, in the inner part of the Arctic Ocean, anomalies of warm advection appear in the region near the Pacif 相似文献
7.
Sea surface temperature (SST) and salinity (SSS) time series from four ocean weather stations and data from an integration
of the GFDL coupled ocean-atmosphere model are analyzed to test the applicability of local linear stochastic theory to the
mixed-layer ocean. According to this theory, mixed-layer variability away from coasts and fronts can be explained as a ‘red
noise’ response to the ‘white noise’ forcing by atmospheric disturbances. At one weather station, Papa (northeast Pacific),
this stochastic theory can be applied to both salinity and temperature, explaining the relative redness of the SSS spectrum.
Similar results hold for a model grid point adjacent to Papa, where the relationships between atmospheric energy and water
fluxes and actual changes in SST and SSS are what is expected from local linear stochastic theory. At the other weather stations,
this theory cannot adequately explain mixed-layer variability. Two oceanic processes must be taken into account: at Panulirus
(near Bermuda), mososcale eddies enhance the observed variability at high frequencies. At Mike and India (North Atlantic),
variations in SST and SSS advection, indicated by the coherence and equal persistence of SST and SSS anomalies, contribute
to much of the low frequency variability in the model and observations. To achieve a global perspective, TOPEX altimeter data
and model results are used to identify regions of the ocean where these mechanisms of variability are important. Where mesoscale
eddies are as energetic as at Panulirus, indicated by the TOPEX global distribution of sea level variability, one would expect
enhanced variability on short time scales. In regions exhibiting signatures of variability similar to Mike and India, variations
in SST and SSS advection should dominate at low frequencies. According to the model, this mode of variability is found in
the circumpolar ocean and the northern North Atlantic, where it is associated with the irregular oscillations of the model’s
thermohaline circulation.
Received: 11 March 1996 / Accepted: 6 September 1996 相似文献
8.
本文分析了中国科学院大气物理研究所年代际气候预测系统IAP DecPreS的海洋同化试验（简称EnOI-IAU试验）在西北太平洋地区的海表面温度（SST）年循环的模拟技巧,并通过对比IAP DecPreS系统自由耦合历史气候模拟试验结果,在包含海气耦合过程的框架下讨论了耦合模式中西北太平洋夏季SST模拟差异,及其对亚洲季风区夏季季风降水模拟的影响。结果表明,EnOI-IAU试验较好地模拟出了西北太平洋各个季节的SST空间分布,并显著减小了原存在于历史气候模拟试验中持续全年的SST冷偏差。混合层热收支诊断分析表明,包含同化过程在内的海洋过程的模拟差异对西北太平洋海温的模拟提升有重要贡献。夏季,EnOI-IAU试验模拟的印度季风伴随的低层西风较观测偏东、偏强,且高估了赤道西太平洋区域的降水量值、低估了印度洋区域的降水量值。水汽收支分析显示,气旋式环流异常造成的水汽辐合异常是造成亚洲季风区降水模拟差异的主要原因。研究表明,较之历史模拟试验,EnOI-IAU试验中夏季西北太平洋地区SST增暖造成局地对流增强,进而使得局地产生异常上升运动,水汽辐合增强,造成西北太平洋地区降水模拟偏多,激发出低层西风异常及赤道外气旋式环流异常。该低层西风异常导致了北印度洋地区低层辐散异常,减小了原存在于历史试验中印度洋地区的正降水偏差。西北太平洋气旋式环流异常一方面增强了印度夏季风伴随的低层西风,使得更多的水汽从阿拉伯海输送到西太平洋暖池区域,增强了该区域的降水量;另一方面,该气旋式环流异常减小了历史模拟试验中中国南部区域偏强的低层风速,进而提升了模式对东亚低层西南风的模拟能力。 相似文献
9.
T. Furevik M. Bentsen H. Drange I. K. T. Kindem N. G. Kvamstø A. Sorteberg 《Climate Dynamics》2003,21(1):27-51
A new coupled atmosphere–ocean–sea ice model has been developed, named the Bergen Climate Model (BCM). It consists of the atmospheric model ARPEGE/IFS, together with a global version of the ocean model MICOM including a dynamic–thermodynamic sea ice model. The coupling between the two models uses the OASIS software package. The new model concept is described, and results from a 300-year control integration is evaluated against observational data. In BCM, both the atmosphere and the ocean components use grids which can be irregular and have non-matching coastlines. Much effort has been put into the development of optimal interpolation schemes between the models, in particular the non-trivial problem of flux conservation in the coastal areas. A flux adjustment technique has been applied to the heat and fresh-water fluxes. There is, however, a weak drift in global mean sea-surface temperature (SST) and sea-surface salinity (SSS) of respectively 0.1 °C and 0.02 psu per century. The model gives a realistic simulation of the radiation balance at the top-of-the-atmosphere, and the net surface fluxes of longwave, shortwave, and turbulent heat fluxes are within observed values. Both global and total zonal means of cloud cover and precipitation are fairly close to observations, and errors are mainly related to the strength and positioning of the Hadley cell. The mean sea-level pressure (SLP) is well simulated, and both the mean state and the interannual standard deviation show realistic features. The SST field is several degrees too cold in the equatorial upwelling area in the Pacific, and about 1 °C too warm along the eastern margins of the oceans, and in the polar regions. The deviation from Levitus salinity is typically 0.1 psu – 0.4 psu, with a tendency for positive anomalies in the Northern Hemisphere, and negative in the Southern Hemisphere. The sea-ice distribution is realistic, but with too thin ice in the Arctic Ocean and too small ice coverage in the Southern Ocean. These model deficiencies have a strong influence on the surface air temperatures in these regions. Horizontal oceanic mass transports are in the lower range of those observed. The strength of the meridional overturning in the Atlantic is 18 Sv. An analysis of the large-scale variability in the model climate reveals realistic El Niño – Southern Oscillation (ENSO) and North Atlantic–Arctic Oscillation (NAO/AO) characteristics in the SLP and surface temperatures, including spatial patterns, frequencies, and strength. While the NAO/AO spectrum is white in SLP and red in temperature, the ENSO spectrum shows an energy maximum near 3 years. 相似文献
10.
海洋环流对全球增暖趋势的调制：基于FGOALS-s2的数值模拟研究 总被引：1，自引：0，他引：1
在工业革命以来全球长期增暖趋势背景下,全球平均表面气温还同时表现出年代际变化特征,二者叠加在一起使得全球平均气温在某些年份增暖相对停滞(如1999～2008年)或者增暖相对较快(如1980～1998年).利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG)发展的耦合气候模式FGOALS-s2历史气候和典型路径浓度(RCPs)模拟试验结果研究了可能造成全球增暖的年代际停滞及加速现象的原因,特别是海洋环流对全球变暖趋势的调制作用.该模式模拟的全球平均气温与观测类似,即在长期增暖趋势之上,还叠加了显著的年代际变化.对全球平均能量收支分析表明,模拟的气温年代际变化与大气顶净辐射通量无关,意味着年代际表面气温变化可能与能量在气候系统内部的重新分配有关.通过对全球增暖加速和停滞时期大气和海洋环流变化的合成分析及回归分析,发现全球表面气温与大部分海区海表温度(SST)均表现出几乎一致的变化特征.在增暖停滞时期,SST降低,更多热量进入海洋次表层和深层,使其温度增加;而在增暖加速时期,更多热量停留在表层,使得大部分海区SST显著增加,次表层海水和深海相对冷却.进一步分析表明,热带太平洋表层和次表层海温年代际变化主要是由于副热带—热带经圈环流(STC)的年代际变化所致,然后热带太平洋海温异常可以通过风应力和热通量强迫作用引起印度洋、大西洋海温的年代际变化.在此过程中,海洋环流变化起到了重要作用,例如印度尼西亚贯穿流(ITF)年代际异常对南印度洋次表层海温变化起到关键作用,而大西洋经圈翻转环流(AMOC)则能直接影响到北大西洋深层海温变化. 相似文献
11.
利用CMIP5提供的25个工业革命前控制试验(piControl)模拟数据评估了热带太平洋两类El Ni(n)o(即东部EP和中部CP型El Ni(n)o)的海表盐度(SSS)空间结构差异及其与海表温度(SST)和降水的关系.结果表明:(1)大部分模式能够模拟出EP和CP型空间结构,两类El Ni(n)o中的SST、降水和SSS的空间技巧评分依次减小,其中,EP型SST和降水水平分布的模拟能力强于CP型,SSS则为CP型强于EP型,CP型模拟的SST、SSS和降水异常中心位置较EP型偏西且强度偏弱;(2) CP型SST、降水和SSS三者空间分布的线性一致性比EP型好,即在CP型中,SST影响降水,进而影响SSS,同时SSS对SST调制的反馈机制较显著,而对于EP型,由于海洋水平平流和非局地效应等因素,使得SST与SSS空间对应较差;(3)依据多模式模拟的SSS空间技巧评分高低将CMIP5模式分为两类,技巧评分低(高)的模式模拟的SST、SSS和降水异常值的中心位置偏西(偏东),引起中心位置偏移的原因与模式模拟赤道太平洋冷舌的位置有关,即赤道太平洋冷舌西伸显著,导致发生El Ni(n)o时SST异常变暖西伸显著,进而使得降水异常和SSS异常位置偏西.同时,技巧评分低的模式还易出现向东南延伸的负SSS异常,原因是双赤道辐合带的东南分支过于明显,即降水偏多,导致SSS偏淡.SSS变化会影响ENSO的发生发展.因此,探讨两类El Ni(n)o盐度分布的差异及相关物理场的关系,为提高模式的气候模拟和预测提供有益的借鉴. 相似文献
12.
利用CMIP5提供的25个工业革命前控制试验（piControl）模拟数据评估了热带太平洋两类El Ni?o（即东部EP和中部CP型El Ni?o）的海表盐度（SSS）空间结构差异及其与海表温度（SST）和降水的关系。结果表明:（1）大部分模式能够模拟出EP和CP型空间结构,两类El Ni?o中的SST、降水和SSS的空间技巧评分依次减小,其中,EP型SST和降水水平分布的模拟能力强于CP型,SSS则为CP型强于EP型,CP型模拟的SST、SSS和降水异常中心位置较EP型偏西且强度偏弱;（2）CP型SST、降水和SSS三者空间分布的线性一致性比EP型好,即在CP型中,SST影响降水,进而影响SSS,同时SSS对SST调制的反馈机制较显著,而对于EP型,由于海洋水平平流和非局地效应等因素,使得SST与SSS空间对应较差;（3）依据多模式模拟的SSS空间技巧评分高低将CMIP5模式分为两类,技巧评分低（高）的模式模拟的SST、SSS和降水异常值的中心位置偏西（偏东）,引起中心位置偏移的原因与模式模拟赤道太平洋冷舌的位置有关,即赤道太平洋冷舌西伸显著,导致发生El Ni?o时SST异常变暖西伸显著,进而使得降水异常和SSS异常位置偏西。同时,技巧评分低的模式还易出现向东南延伸的负SSS异常,原因是双赤道辐合带的东南分支过于明显,即降水偏多,导致SSS偏淡。SSS变化会影响ENSO的发生发展。因此,探讨两类El Ni?o盐度分布的差异及相关物理场的关系,为提高模式的气候模拟和预测提供有益的借鉴。 相似文献
13.
Spring rainfall secular variability is studied using observations, reanalysis, and model simulations. The joint coherent spatio-temporal secular variability of gridded monthly gauge rainfall over Ethiopia, ERA-Interim atmospheric variables and sea surface temperature (SST) from Hadley Centre Sea Ice and SST (HadISST) data set is extracted using multi-taper method singular value decomposition (MTM-SVD). The contemporaneous associations are further examined using partial Granger causality to determine presence of causal linkage between any of the climate variables. This analysis reveals that only the northwestern Indian Ocean secular SST anomaly has direct causal links with spring rainfall over Ethiopia and mean sea level pressure (MSLP) over Africa inspite of the strong secular covariance of spring rainfall, SST in parts of subtropical Pacific, Atlantic, Indian Ocean and MSLP. High secular rainfall variance and statistically significant linear trend show consistently that there is a massive decline in spring rain over southern Ethiopia. This happened concurrently with significant buildup of MSLP over East Africa, northeastern Africa including parts of the Arabian Peninsula, some parts of central Africa and SST warming over all ocean basins with the exception of the ENSO regions. The east-west pressure gradient in response to the Indian Ocean warming led to secular southeasterly winds over the Arabian Sea, easterly over central Africa and equatorial Atlantic. These flows weakened climatological northeasterly flow over the Arabian Sea and southwesterly flow over equatorial Atlantic and Congo basins which supply moisture into the eastern Africa regions in spring. The secular divergent flow at low level is concurrent with upper level convergence due to the easterly secular anomalous flow. The mechanisms through which the northwestern Indian Ocean secular SST anomaly modulates rainfall are further explored in the context of East Africa using a simplified atmospheric general circulation model (AGCM) coupled to mixed-layer oceanic model. The rainfall anomaly (with respect to control simulation), forced by the northwestern Indian Ocean secular SST anomaly and averaged over the 30-year period, exhibits prevalence of dry conditions over East and equatorial Africa in agreement with observation. The atmospheric response to secular SST warming anomaly led to divergent flow at low levels and subsidence at the upper troposphere over regions north of 5° S on the continent and vice versa over the Indian Ocean. This surface difluence over East Africa, in addition to its role in suppressing convective activity, deprives the region of moisture supply from the Indian Ocean as well as the Atlantic and Congo basins. 相似文献
14.
本文通过与观测和再分析资料的对比,评估了LASG/IAP发展的气候系统模式FGOALS的两个版本FGOALS-g2和FGOALS-s2对南亚夏季风的气候态和年际变率的模拟能力,并使用水汽收支方程诊断,研究了造成降水模拟偏差的原因。结果表明,两个模式夏季气候态降水均在陆地季风槽内偏少,印度半岛附近海域偏多,在降水年循环中表现为夏季北侧辐合带北推范围不足。FGOALS-g2中赤道印度洋"东西型"海温偏差导致模拟的东赤道印度洋海上辐合带偏弱,而FGOALS-s2中印度洋"南北型"海温偏差导致模拟的海上辐合带偏向西南。水汽收支分析表明,两个模式中气候态夏季风降水的模拟偏差主要来自于整层积分的水汽通量,尤其是垂直动力平流项的模拟偏差。一方面,夏季阿拉伯海和孟加拉湾的海温偏冷而赤道西印度洋海温偏暖,造成向印度半岛的水汽输送偏少;另一方面,对流层温度偏冷,冷中心位于印度半岛北部对流层上层,同时季风槽内总云量偏少,云长波辐射效应偏弱,对流层经向温度梯度偏弱以及大气湿静力稳定度偏强引起的下沉异常造成陆地季风槽内降水偏少。在年际变率上,观测中南亚夏季风环流和降水指数与Ni?o3.4指数存在负相关关系,但FGOALS两个版本模式均存在较大偏差。两个模式中与ENSO暖事件相关的沃克环流异常下沉支和对应的负降水异常西移至赤道以南的热带中西印度洋,沿赤道非对称的加热异常令两个模式中越赤道环流季风增强,导致印度半岛南部产生正降水异常。ENSO相关的沃克环流异常下沉支及其对应的负降水异常偏西与两个模式对热带南印度洋气候态降水的模拟偏差有关。研究结果表明,若要提高FGOALS两个版本模式对南亚夏季风气候态模拟技巧,需减小耦合模式对印度洋海温、对流层温度及云的模拟偏差;若要提高南亚夏季风和ENSO相关性模拟技巧需要提高模式对热带印度洋气候态降水以及与ENSO相关的环流异常的模拟能力。 相似文献
15.
我国夏季降水与全球海温的耦合关系分析 总被引：15，自引：4，他引：15
利用我国160个台站从1951~2000年的月降水观测资料和NCEP/NCAR的全球海表温度(SST)资料,分析了我国夏季(6、7、8月)降水的时空变化特征及其与海温的相关,并应用奇异值分解(SVD)方法研究了我国夏季降水分布异常与海温变化的耦合关系。结果表明,我国夏季降水异常的雨型分布主要有3种,这些雨型的时间变化除了有明显的年际变化外,还存在显著的年代际变化。尤其是华北地区的降水从1965年左右开始减少,特别是大约1976年后有显著的减少。SVD分析揭示的我国夏季降水和全球海温异常的耦合关系表明,这种耦合关系最主要的时空变化特征表现在年代际变化的时间尺度上。我国华北和东北南部的夏季降水从1976年前后明显减少,与之显著关联的海温异常的关键区包括太平洋、印度洋以及热带和南大西洋。特别是热带中、东太平洋,印度洋,以及热带和南大西洋海水,从1976年前后也明显增暖。本研究揭示的华北持续干旱与印度洋和大西洋海温的年代际变化的耦合关系,在以往的研究中还未见到,因而有必要在今后的研究中加以重视。我国夏季降水和海温的耦合关系,还表现在长江中下游地区的降水异常与太平洋和大西洋海温异常的显著相关上。当南海和黑潮区域以及相邻的热带西太平洋海区海温为正异常时,热带和北大西洋海温也为正异常;而热带中、东太平洋海温为负异常时,长江中下游地区往往偏涝;反之,该地区则偏旱。 相似文献
16.
利用1979—2019年Hadley中心的海表温度资料、GPCP的降水资料以及NCEP-DOE的再分析资料等,分析了北半球春季热带南大西洋海表温度异常与北半球夏季亚澳季风区降水异常的联系。研究表明,北半球春季热带南大西洋海表温度异常与随后夏季热带西太平洋到南海（澳大利亚东侧海域到热带东印度洋）地区的降水异常为显著负相关（正相关）关系。北半球春季热带南大西洋的海表温度正异常可以引起热带大西洋和热带太平洋间的异常垂直环流,其中异常上升支（下沉支）位于热带大西洋（热带中太平洋）。热带中太平洋的异常下沉气流和低层辐散气流引起热带中西太平洋低层的异常东风,后者有利于热带中东太平洋海表温度出现负异常。通过Bjerknes正反馈机制,热带中东太平洋海表温度异常从北半球春季到夏季得到发展。热带中东太平洋海表温度负异常激发的Rossby波使得北半球夏季热带西太平洋低层出现一对异常反气旋。此时,850 hPa上热带西太平洋到海洋性大陆地区为显著的异常东风,有利于热带西太平洋到南海（澳大利亚东侧海域到热带东印度洋）地区出现异常的水汽辐散（辐合）,导致该地区降水减少（增加）。 相似文献
17.
基于美国国家航天局（NASA）发射的水瓶座（Aquarius/SAC-D）卫星和欧洲航天局（ERA）发射的土壤湿度与海洋盐度（SMOS）卫星的观测资料,以及Argo海表盐度资料,重点分析了阿拉伯海中北部海表盐度的季节和年际变化.年平均情况下,Argo、Aquarius和SMOS表现出相似的海表盐度分布形态,均表现了阿拉伯海中北部高达36.5 psu的高盐特征.阿拉伯海中北部海表盐度在2—3月出现最低值,在4月之后快速升高,并在夏季西南季风的成熟阶段达到最高.阿拉伯海中北部海表盐度显著的季节变化与季风风场引起的大量蒸发和平流输送相关.夏季风期间,Ras al Hadd急流将来自阿曼湾的高盐水向东向南输送到阿拉伯海中北部海域,使海表盐度升高并达到最高值;冬季风期间,冬季风环流系统在印度半岛西侧海域形成向北的低盐水输送,造成阿拉伯海中北部海表盐度降低.该低盐水平流在冬季风后期能够影响到阿曼海.阿拉伯海中北部海表盐度年际变化主要与季风驱动的季风环流系统的变化相关,尤其是冬季风期间向北流动的印度西侧沿岸流的强弱与该区域海表盐度年际变化关系密切. 相似文献
18.
This study depicts the sub-seasonal prediction of the South China Sea summer monsoon onset (SCSSMO) and investigates the associated oceanic and atmospheric processes, utilizing the hindcasts of the National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 (CFSv2). Typically, the SCSSMO is accompanied by an eastward retreat of the western North Pacific subtropical high (WNPSH), development of the cross-equatorial flow, and an increase in the east-west sea surface temperature (SST) gradient. These features are favorable for the onset of westerlies and strengthening of convection and precipitation over the South China Sea (SCS). A more vigorous SCSSMO process shows a higher predictability, and vice versa. The NCEP CFSv2 can successfully predict the onset date and evolution of the monsoon about 4 pentads (20 days) in advance (within 1–2 pentads) for more forceful (less vigorous) SCSSMO processes. On the other hand, the climatological SCSSMO that occurs around the 27th pentad can be accurately predicted in one pentad, and the predicted SCSSMO occurs 1–2 pentads earlier than the observed with a weaker intensity at longer leadtimes. Warm SST biases appear over the western equatorial Pacific preceding the SCSSMO. These biases induce a weaker-than-observed WNPSH as a Gill-type response, leading to weakened low-level easterlies over the SCS and hence an earlier and less vigorous SCSSMO. In addition, after the SCSSMO, remarkable warm biases over the eastern Indian Ocean and the SCS and cold biases over the WNP induce weaker-than-observed westerlies over the SCS, thus also contributing to the less vigorous SCSSMO. 相似文献
19.
Seasonal to interannual climate predictability in mid and high northern latitudes in a global coupled model 总被引：3，自引：2，他引：1
The upper limit of climate predictability in mid and high northern latitudes on seasonal to interannual time scales is investigated
by performing two perfect ensemble experiments with the global coupled atmosphere–ocean–sea ice model ECHAM5/MPI-OM. The ensembles
consist of six members and are initialized in January and July from different years of the model’s 300-year control integration.
The potential prognostic predictability is analyzed for a set of oceanic and atmospheric climate parameters. The predictability
of the atmospheric circulation is small except for southeastern Europe, parts of North America and the North Pacific, where
significant predictability occurs with a lead time of up to half a year. The predictability of 2 m air temperature shows a
large land–sea contrast with highest predictabilities over the sub polar North Atlantic and North Pacific. A combination of
relatively high persistence and advection of sea surface temperature anomalies into these areas leads to large predictability.
Air temperature over Europe, parts of North America and Asia shows significant predictability of up to half a year in advance.
Over the ice-covered Arctic, air temperature is not predictable at time scales exceeding 2 months. Sea ice thickness is highly
predictable in the central Arctic mainly due to persistence and in the Labrador Sea due to dynamics. Surface salinity is highly
predictable in the Arctic Ocean, northern North Atlantic and North Pacific for several years in advance. We compare the results
to the predictability due to persistence and show the importance of dynamical processes for the predictability. 相似文献
20.
The role of tropical Atlantic sea surface temperature (SST) anomalies during ENSO episodes over northeast Brazil (Nordeste) is investigated using the CPTEC/COLA Atmospheric General Circulation Model (AGCM). Four sets of integrations are performed using SST in El Niño and La Niña (ENSO) episodes, changing the SST of the Atlantic Ocean. A positive dipole (SST higher than normal in the tropical North Atlantic and below normal in the tropical South Atlantic) and a negative dipole (opposite conditions), are set as the boundary conditions of SST in the Atlantic Ocean. The four experiments are performed using El Niño or La Niña SST in all oceans, except in the tropical Atlantic where the two phases of the SST dipole are applied. Five initial conditions were integrated in each case in order to obtain four ensemble results. The positive SST dipole over the tropical Atlantic Ocean and El Niño conditions over the Pacific Ocean resulted in dry conditions over the Nordeste. When the negative dipole and El Niño conditions over the Pacific Ocean were applied, the results showed precipitation above normal over the north of Nordeste. When La Niña conditions over Pacific Ocean were tested together with a negative dipole, positive precipitation anomalies occurred over the whole Nordeste. Using the positive dipole over the tropical Atlantic, the precipitation over Nordeste was below average. During La Niña episodes, the Atlantic Ocean conditions have a larger effect on the precipitation of Nordeste than the Pacific Ocean. In El Niño conditions, only the north region of Nordeste is affected by the Atlantic SST. Other tropical areas of South America show a change only in the intensity of anomalies. Central and southeast regions of South America are affected by the Atlantic conditions only during La Niña conditions, whereas during El Niño these regions are influenced only by conditions in the Pacific Ocean. 相似文献