对流层及平流层低层全球动能的季节性急变

利用１９８０－１９８８年ＥＣＭＷＦ的资料，分析对流层５００ｈＰａ，３００ｈＰａ和平流层低层１００ｈＰａ全球范围的纬向平均动能和涡动动能的季节过渡，比较不同层次不同纬度带动能模态的季节性急变，得到如下结论：（１）北半球热带与温带各层次的ＫＺ都有季节性急变，发生在３－４月和１０月附近，而南半球仅在热带有急变。（２）北半球热带地区ＫＺ在６月还有一次季节性急变，出现有１００ｈＰａ和５００ｈＰａ．（３）１０     

全球500kPa角动量与EP通量的季节变化

利用ＥＣＭＷＦ提供的９ａ（１９８Ｏ－１９８８）资料，从定性和定量角度分析５００ｈＰａ全球东西风带的角动量和ＥＰ通量的季节过渡。结果发现：不仅角动量存在明显的季节性急变，而且反映波活动的ＥＰ通量也存在相应的季节性急变。另外，季节性急变的发生时间在东西风带亦有所不同。     

500hPa全球动能年际变率及1983和1987年两个厄尼诺年动能距平的差异

利用１９８０—１９８８年９年期间ＥＣＭＷＦ５００ｈＰａ全球风场资料，计算７个“纬度带”上三种基本动能模态，研究这些动能模态的各年异常情况。结果表明，１９８３年是这９年内动能唯一的正值异常年，而１９８７年和１９８５年动能基本上属于正常年，只有个别动能模态有异常。这说明，１９８０年代两个厄尼诺年的异常情况有很大的差异。动能模态与赤道东太平洋海温距平（ＳＳＴＡ）的后延相关表明，１９８３年事件的影响可以波及范围相当广泛甚至波及全球大气，而１９８７年事件所能影响的范围远比１９８３年事件要小。此外，还表明北半球副热带急流轴附近是对ＳＳＴＡ响应的敏感地区。     

全球不同纬度带平均有效位能的季节急变

利用1980～1988年ECMWF的资料，计算了对流层500 hPa、300 hPa和平流层100 hPa逐日和月平均的纬向平均有效位能（PZ），分析其季节过渡，比较不同纬度带的季节性急变。结果表明，在4月和10月附近，各纬度带上均可出现PZ的急变。而且用逐日资料还可分析出6月急变。在北半球对流层高层（100 hPa）PZ的季节性急变不如低层（500 hPa）明显，而在南半球PZ的季节性急变与北半球相反，高层比低层明显。     

Trace gas measurements at the monitoring station cape point,South Africa,between 1978 and 1988

Since 1978, a measuring station has been operated at Cape Point (34°21 S, 18°29 E). In this article, results of measurements of CO, CFCl₃, CCl₄, O₃, N₂O and CH₄ are presented as monthly means and analyzed with respect to long-term trends and seasonal variations. For CO and CH₄, very similar seasonal variations have been observed, indicating strong interrelations between these two gases. For CO and O₃, no significant changes of the mean annual concentrations can be established for the observation periods of 10 and 5 years, respectively. The measurements yield a growth rate of 9.1 pptv yr^-1 for CFCl₃ (1980–1987) and 0.6 ppbv yr^-1 for N₂O (1983–1987). The concentration increases of CH₄ (10.3 ppbv yr^-1 for 1983–1987) and of CCl₄ (2.1 pptv yr^-1 for 1980–1988) are analyzed for temporal changes during the last years.Presented at the Second Conference on Baseline Observations in Atmospheric Chemistry (SABOAC II) in Melbourne, Australia, November 1988.     

南亚、东南亚地区大气环流季节突变的多年状况

在已有研究成果的基础上，本文利用FGGE-IIIb资料及欧洲中期天气预报中心（ECMWF）1980至1988年七层全球分析资料，分析了1979至1988年南亚、东南亚地区由冬至夏大气环流季节突变的状况。利用与这一地区主要天气系统密切相关的某些大气环流指标来描述该地区的季节突变，并根据这些指标的逐候演变、信噪比及候平均环流形势确定了突变发生的时段。在此基础上，本文讨论了季节突变的多年状况，用多年资料证实了南亚、东南亚地区由冬至夏季节演变过程存在着两次突变，分析了突变方式在区域间、高低层间及年际间的差异。     

热带500百帕动能的基本特征与季节变化——南、北半球的比较

本文利用1980—1988年30°S—30°N的风场资料,计算了逐日的平均动能,涡动动能及相互转换和波数域动能;并分析了南、北半球热带对流层中层动能的演变特征,季节调整规律,指出了热带与中高纬动能的差异。      

北太平洋风暴轴“深冬抑制”现象的能量分析

采用欧洲中期天气预报中心逐日再分析资料（ERA-40）,从局地能量变化方程出发,通过分析北太平洋风暴轴区域对流层不同层次局地能量的季节演变过程,对风暴轴区域各能量项在“深冬抑制”现象中的作用进行了深入探讨。结果表明,天气尺度扰动动能的季节变化可以很好地反映北太平洋风暴轴的“深冬抑制”现象,并且该现象在对流层上层最为显著,其发生概率约为80％,其中20世纪70年代中后期到80年代前期抑制最强。从同期各能量项的变化来看,扰动动能的变化主要受斜压能量转换项、涡动非地转位势通量的散度项和正压能量转换项的影响。在深冬季节,由于消耗扰动动能的正压能量转换项虽有些微弱减少从而使得扰动动能有所增加,但为风暴轴提供扰动动能的斜压能量转换项和涡动非地转位势通量的散度项减少的幅度却更大,因而总的效果是扰动动能大为减小,这可能是造成北太平洋风暴轴“深冬抑制”现象的直接原因。     

Suburban-rural energy balance comparisons in summer for Vancouver,B.C.

Simultaneous energy balance observations at a rural and a suburban site in Vancouver, B.C. during the summer of 1983 are presented. The study is a follow-up to that conducted in 1980. Many of the 1980 results were unexpected and the present study seeks to assess their representativeness. The net radiant, turbulent sensible, and rural soil heat flux densities were measured directly. The suburban heat storage was parameterized and the turbulent latent heat flux densities were resolved as residuals in the energy balances. The 1983 average diurnal energy partitioning for both sites was typical of those quoted in the literature, suggesting that the 1980 results represent an extreme case. Suburban-rural differences showed the suburban area to have a 4% increase in net radiation, a 51% increase in turbulent sensible heat, and a 46% decrease in turbulent latent heat flux density. The values of the average daytime Bowen ratio were 0.46 and 1.28 for the rural and suburban areas, respectively. The sensible heat flux density exhibited relatively large values in the late afternoon and remained directed upward on many summer evenings. Large day-to-day variability in the relative magnitude of the suburban turbulent fluxes may have been due to synoptic influences. In this environment, the turbulent surface and mixed layers are closely coupled because of the low aerodynamic resistance over the rough surface.     

Role of Triad Kinetic Energy Interactions for Maintenance of Upper Tropospheric Low Frequency Waves during Summer Monsoon 1988

ＲｏｌｅｏｆＴｒｉａｄＫｉｎｅｔｉｃＥｎｅｒｇｙＩｎｔｅｒａｃｔｉｏｎｓｆｏｒＭａｉｎｔｅｎａｎｃｅｏｆＵｐｐｅｒＴｒｏｐｏｓｐｈｅｒｉｃＬｏｗＦｒｅｑｕｅｎｃｙＷａｖｅｓｄｕｒｉｎｇＳｕｍｍｅｒＭｏｎｓｏｏｎ１９８８Ｄ．Ｒ．Ｃｈａｋｒａｂｏｒｔｙａ...     

Seasonal snowline instability in an energy balance model

The stability properties of a seasonal, one dimensional energy balance climate model are examined. The model contains idealized landsea geography, an interactive moving snowline and high space-time resolution. For a polar land cap surrounded by ocean we find a bifurcation in the seasonal cycle solutions as a function of solar constant leading to qualitatively different climate regimes: one with continental snow-free summers and the other with perennial snow cover over a large area surrounding the pole. In the parameterspace neighborhood of a bifurcation an infinitesimal change in any radiation budget parameter can cause the transition from one state to the other. Of special interest to those planning more elaborate numerical experiments (GCMs) is the result that 10s of seasonal cycles may be necessary for the model to damp out transient effects before settling upon a repeating seasonal cycle if parameter values are such that the solution is near a bifurcation. This latter finding is unexpected, since the longest time scale in the linear version of the energy balance model is about 5 years.     

季风区环流季节变化及其在El Nino年的异常

该文用EOF分析方法研究了1981～1983年5～9月印度洋、西太平洋季风区环流的季节变化及其年际异常。所得第1特征向量是季风分量。其1983年的时间系数曲线与1981、1982年的差异表明，El Nino年夏季风环流弱，且其向北半球夏季型的转变期较正常年推迟。在西太平洋地区它表现为副高北进的滞后。用IAP GCM作的一个相应的数值试验证实了上述结果的正确。     

气候变暖背景下我国南方旱涝灾害时空格局变化

我国南方地区各季节降水异常主要包含三种优势模态：长江及其以南地区降水呈整体偏多或偏少的一致型,长江中下游流域与华南呈反相变化的南北反相型以及东南与西南呈反相变化的东西反相型。其中一致型是南方地区各季节降水变率的第一优势模态。总体而言,在1961—2013年南方地区平均降水存在明显的年代际和长期趋势变化。其中,夏季和冬季南方区域平均降水具有相似的年代际变化特征,而秋季降水的年代际演变几乎与上述两个季节的相反。不过,在近30年南方各季降水量发生年代际转折的时间不尽相同：春季和秋季降水分别在21世纪初期和20世纪80年代中后期之后进入干位相,冬季和夏季降水则分别在80年代中期和90年代初期之后进入湿位相。自21世纪初期以来,南方夏季和冬季降水逐渐转入中性位相。此外,南方春季和秋季降水均呈减少趋势;而夏季和冬季则相反,均呈增多趋势。对于西南地区,除了春季外,其他三个季节的降水均呈减少趋势,出现了季节连旱的特征,尤其是秋旱最为严重。不过,不管是季节降水量还是旱/涝日数,在我国南方大部分地区其线性变化趋势并不十分显著,这与南方降水年代际分量对降水变率存在较大贡献相关。分析还发现,我国南方区域洪涝受灾面积具有比较明显的年代际变化,而干旱受灾面积则没有明显的年代际变化特征,近十多年来西南地区干旱和洪涝受灾出现了交替互现的特点。     

1961~2003年中国大陆地表太阳总辐射变化趋势

利用中国大陆30个气象站1961～2003年地表太阳总辐射观测数据,研究了辐射年总量和季节总量的变化趋势及其空间分布特征,并探讨了其原因。结果表明:1961～1989年中国大陆地表太阳总辐射总体呈减少趋势,减少约11%;1990～2003年间略有回升,但其均值仍比1961～1965年的均值低8.2%。大部分地区春夏两季减少明显,约占年减少量的55%～85%。对各站点观测数据的趋势分析表明,地表太阳总辐射随时间的变化大致可分为4种类型,其特征分别为:1961～2003年间持续减少(占总站点数20%);20世纪60年代初到80年代中期呈显著减少趋势,其后线性趋势不明显(占总站点数40%)或呈逐步增加趋势(占总站点数16.7%);1961～2003年间无显著变化(占总站点数23.3%)。这4种类型在空间分布上无明显的区域特征。日照时数减少是总辐射减少的主要原因,可以解释地表太阳辐射年总量变化的72%,日照时数随风速的增大而增加。     

东北地区夏季降水时空变化特征

采用东北地区99个测站1960～2000年逐日降水资料，运用小波分析、突变分析、旋转EOF等方法，研究了东北地区不同区域夏季降水的长期变化特征。结果表明，东北地区夏季降水呈减少趋势，并存在14年和2～4年的变化周期。东北地区夏季降水异常可分为5种空间分布类型：东北西南部型、东北东南部型，东北东北部型、东北西北部型、东北中部型。东北东南部地区夏季降水减少趋势最明显，东北西南部降水的增加趋势最明显。各区域降水的变化周期有所区别，东北东北部存在16～18年的变化周期，其它地区存在10～14年的变化周期，各区域降水突变的时间主要在60年代和80年代。     

The impact of ecosystem functional type changes on the La Plata Basin climate

In this paper, the effects of land cover changes on the climate of the La Plata Basin in southern South America are investigated using the Weather and Research Forecasting (WRF) Model configured on a 30/10km two-way interactive nested grid. To assess the regional climate changes resulting from land surface changes, the standard land cover types are replaced by time-varying Ecosystem Functional Types (EFTs), which is a newly devised land-cover classification that characterizes the spatial and interannual variability of surface vegetation dynamics. These variations indicate that natural and anthropogenic activities have caused changes in the surface physical parameters of the basin, such as albedo and roughness length, that contributed to regional climate changes. EFTs are obtained from functional attributes of vegetation computed from properties of the Normalized Difference Vegetation Index (NDVI) to represent patches of the land surface with homogeneous energy and gas exchanges with the atmosphere. Four simulations are conducted, each experimental period ranging from September to November in two contrasting years, 1988 and 1998. The influence of an identical EFT change on the surface heat fluxes, 2-m temperature and humidity, 10-m winds, convective instabilities and large-scale moisture fluxes and precipitation are explored for 1988 (a dry year) and 1998 (a wet year). Results show that the surface and atmospheric climate has a larger response to the same EFT changes in a dry year for 2-m temperature and 10-m wind; the response is larger in a wet year for 2-m water vapor mixing ratio, convective available potential energy, vertically integrated moisture fluxes and surface precipitation. For EFTs with high productivity and a weak seasonal cycle, the nearsurface temperature during the spring of 1988 and 1998 increased by as much as 1℃ in the central and western portions of La Plata Basin. Additionally, for higher productivity EFTs, precipitation differences were generally positive in both dry and wet years, although the patterns are not uniform and exhibit certain patchiness with drier conditions.     

Kinetic energy exchanges between the time scales of ENSO and the Pacific decadal oscillation

This paper examines the non-linear kinetic energy interactions of the atmospheric ENSO and decadal oscillations over the Pacific. The calculations are based on a 54-year dataset of tropospheric winds from NCEP reanalysis. We verify that the decadal oscillations have two dominant modes, corresponding well to the pentadecadal and bidecadal modes reported in the literature. Energy interactions involving the range of decadal oscillations and the range of ENSO oscillations are considered in the context of kinetic energy exchanges in the frequency domain. We quantify the relative amplitudes and spatial structures of the quadratic and triplet terms of the kinetic energy exchanges over the Pacific and conclude that quadratic interactions with the mean flow are the dominant term in the kinetic-to-kinetic energy exchanges. Additionally, we show that triplet interactions provide a non-trivial contribution to the total. The interactions between the range of decadal oscillations and the range of ENSO oscillations are found to be the strongest near the regions of maximum oscillation amplitude and of the maximum oscillation amplitude gradient. Due to their similar spatial structures, the two dominant ENSO modes and the bidecadal mode are found to interact in a resonant way. The interactions among the range of ENSO modes and the range of decadal modes are found to strengthen the ENSO modes in the equatorial, subtropical and midlatitude belts, and to weaken the decadal modes in all but the equatorial belt.     

近百年东亚冬季气温及其大气环流变化型态

利用最新20世纪近百年再分析气象资料,研究近百年东亚冬季气温变化型及其相关的大气环流型态.结果表明近百年内东亚冬季气温主要有两种变化型:第一是东亚西南与东北相反气温变化型,表现在40°N以南及105°E以西地区(西南地区)气温变化与40°N以北及105°E以东地区(东北地区)变化相反;第二是40°N以南气温一致变化型.与第一种气温变化型耦合的大气模态是500hPa欧亚型遥相关、西伯利亚高压及北大西洋涛动.当欧亚型遥相关负位相,北大西洋涛动正位相及西伯利亚高压减弱时,有利于蒙古和我国105° E以东的区域增温而我国西南地区和青藏高原降温,反之亦然.第二种气温变化型耦合大气模态是500hPa西太平洋型遥相关,北太平洋涛动.当西太平洋型遥相关及北太平洋涛动处于正位相时(北太平洋北负南正),东亚40°N以南地区增温,东亚40°N以北地区降温.耦合的大气模态的型态差异,影响各阶段气温的年际变化.近一百年中,欧亚型遥相关和北大西洋涛动在1984～2010期间的型态最显著,是20世纪80年代东亚显著增暖的原因之一.研究还发现20世纪中期后东亚气温的年际变化与极地环流的变化联系紧密,表现在西伯利亚高压范围东扩并与极地环流联系,也是近百年气温趋势上升的一个原因.     

大尺度土地利用变化对东亚地表能量、水分循环及气候影响的敏感性试验

利用NCAR大气环流模式CAM4.0,针对潜在植被和当代植被的分布情形进行了两组25 a的积分试验,探讨了土地利用变化对东亚地区地表能量平衡、水分循环和气候的可能影响.结果表明:以森林退化、农田迅速增加为主的当代土地利用变化,显著改变地表属性,使得东亚地区不同季节的地表反照率均明显增加,并显著改变东亚地区的冬、春季节的地表能量和水分循环.此外,当代大尺度土地利用变化对东亚地区大气环流也有一定影响,可引起东亚冬季风环流显著加强和东亚夏季较弱的偏南风异常.当代土地利用变化未能引起东亚地区近地面气温的显著变化,但可引起东亚北(南)部地区春季降水的显著增加(减小).