长期天气过程的隔季相关

本文比较全面地讨论了大气中相隔5—7个月的相关现象——隔季相关,指出隔季相关是长期天气过程的一个重要现象,它具有明显的纬度效应和季节变化。进而讨论了这种现象与北太平洋海温的关系。      

近百年ElNino/LaNina事件与北京气候相关性分析

通过对近百年El Nino/La Nina事件与北京气候相关性研究发现，El Nino/La Nina事件与北京夏季（6－8月）降水、平均最高气温（7月）和冬季（1月）平均最低气温之间相互关系显著。El Nino事件与夏季降水、冬季平均最低气温呈负相关，与夏季平均最高气温呈正相关，造成降水减少，气温年较差较大，大陆性增强的气候特点。La Nina事件与夏季降水、冬季平均最低气温呈正相关，与夏季平均最高气温呈负关，使降水增加，气温年较差减小，大陆性减弱的气候特点。     

厄尔尼诺现象和拉尼娜现象与中高纬地区气候的关系

利用概率统计学方法,分析厄尔尼诺现象和拉尼娜现象与中高纬地区四季气温、≥10℃活动积温、初霜、终霜及降水等的关系,对短期气候预测具有较好的参考价值。     

极冰对南方涛动的影响

分析南、北极冰量与南方涛动序列作月、季和年尺度的变化过程线性相关关系，发现北极冰量与南方涛动指数是反相关关系，而南极冰量与南方涛动是正相关。比较而言，南极冰量与南方涛动的关系在月和季尺度上似乎较北极与大气的关系密切些。在各时间尺度序列中以太平洋地区南极极冰的影响表现最明显。分析发现极冰与南方涛动之间存在较复杂的非线性关系。在前期极冰的强信号寻找中，发现极冰与南方涛动在月序列的相关关系上存在周期变化现象。进一步选择相关极值的对应步长建立前期极冰状态激发大气变化的预测统计动力模式，模式对大气序列的解释方差可达０．９０以上。文中还进一步探讨了月序列存在的周期变化的共同因素的影响     

EI Nino现象对东亚夏季风环流影响的初步研究

本文分析了1971—80年发生在南美洲西海岸的EI Nino现象及其对东亚夏季风环流的影响。结果表明,1972和1976年为强的EI Nino年,而1971和1974年为显著的反EI Nino年。还指出,1—6月份南美西海岸的海温与7月份我国东部大部分地区夏季风呈负相关.在EI Nino年,主要环流的特征为:(1)西太平洋副热带高压脊线偏北,强度偏弱.(2)澳大利亚高压位置偏南。(3)赤道缓冲脊强大.ITCZ东伸到太平洋中部。南半球的信风在105°E附近越过赤道之后,于10°N折向东去,流入西太平洋.(4)印度次大陆季风中断.孟湾西南季风直接影响我国东部地区的分量极其有限,在反EI Nino年,上述各系统特征完全相反.我们认为,EI Nino现象的发生,引起夏季风环流系统的变动,最终影响到我国夏季风的强度,这是二者之间遥相关的一种可能过程.      

过去500年印度夏季风降水与ENSO的关系

为了研究大尺度背景场对ENSO和印度夏季风降水关系的调制作用,更好地预报气候变暖背景下印度夏季风降水的年际变化,本文利用重建的10套ENSO指数和印度降水资料,研究了ENSO和印度夏季风降水在过去500 a(1470-1999年)中的关系,其存在的原因以及如何理解这一现象,主要侧重于ENSO对印度夏季风的影响.结果 表...     

北半球夏季海洋性大陆区域降水与南方涛动联系的年代际变化

利用1960—2016年夏季美国国家海洋和大气管理局(NOAA)的月平均降水资料、南方涛动指数SOI以及Niňo3指数资料、NCEP/NCAR再分析资料以及英国哈德莱中心海表温度资料,通过相关分析和回归分析,研究了北半球夏季海洋性大陆区域(Maritime Continent,MC)降水与ENSO联系的年代际变化特征。结果表明:MC地区夏季平均降水与SOI指数的相关自1998年后明显减弱。造成这种现象的原因是:南方涛动指数SOI与海温相关系数在太平洋中部为负的大值中心,且1998年之后海温异常呈中部型。这种SSTA强迫造成1998年后大气视热源异常亦偏于赤道太平洋中部,这有利于通过Gill型响应,使菲律宾以东的对流层低层存在明显的反气旋性环流,辐散增强,从而造成赤道以北降水显著减少,抵消了MC区域内南部地区降水的增加,破坏了原有的SOI为正(负)时MC地区平均降水异常增加(减少)的关系。     

Stochastic Modeling of the Effects of Large-Scale Circulation on Daily Weather in the Southeastern U.S.

Statistical methodology is devised to model time series of daily weather at individual locations in the southeastern U.S. conditional on patterns in large-scale atmosphere–ocean circulation. In this way, weather information on an appropriate temporal and spatial scale for input to crop–climate models can be generated, consistent with the relationship between circulation and temporally and/or spatially aggregated climate data (an exercise sometimes termed `downscaling'). The Bermuda High, a subtropical Atlantic circulation feature, is found to have the strongest contemporaneous correlation with seasonal mean temperature and total precipitation in the Southeast (in particular, stronger than for the El Niño–Southern Oscillation phenomenon). Stochastic models for time series of daily minimum and maximum temperature and precipitation amount are fitted conditional on an index indicating the average position of the Bermuda High. For precipitation, a multi-site approach involving a statistical technique known as `borrowing strength' is applied, constraining the relationship between daily precipitation and the Bermuda High index to be spatially the same. In winter (the time of greatest correlation), higher daily maximum and minimum temperature means and higher daily probability of occurrence of precipitation are found when there is an easterly shift in the average position of the Bermuda High. Methods for determining aggregative properties of these stochastic models for daily weather (e.g., variance and spatial correlation of seasonal total precipitation) are also described, so that their performance in representing low frequency variations can be readily evaluated.     

前期高度场和海温场变化对我国汛期降水的影响

利用1952～2001年我国160个测站汛期降水和前期500 hPa高度场和太平洋海温场资料以及三因子最佳子集回归求最大复相关系数的方法,把前期不同时间步长、不同时段的高度场和海温场同时作为预报因子与汛期降水求相关.结果发现:前期两个场共同作为预报因子比把其中某场单独作为预报因子的相关要好.并且存在着较好的"隔多季度相关"现象.预报因子具有实际预报意义的最佳时段为上一年的6～9月.影响我国汛期降水的最佳预报因子主要集中于高度场和海温场具有重要天气气候意义的关键区域.汛期降水可预报性在北方和长江以南均较好.     

Possible linkage between East Asian summer drought and North Pacific Oscillation

The May North Pacific Oscillation Index and the summer (May and June?CJuly?CAugust??JJA) Effective Drought Index have a strong negative correlation in the East Asian region, particularly in northern China, Korea, and the southwestern regions of Japan (here termed ??Northeast Asia??); this signifies an intensification of the summer drought during positive North Pacific Index (NPI) phase in this region, and the presence of such a phenomenon has been observed in this study. The low-south/high-north anomalous pressure pattern forming in all layers of the troposphere in Northeast Asian region has been a cause of drought. This unusual pressure pattern gives rise to a cold northeasterly and intensifies downward flow and reduces relative humidity. In addition, this cold northeasterly hinders the northward movement of the western North Pacific high and reduces the frequency of tropical cyclones passing through this region, thereby further intensifying drought.     

中国极端温度的群发性研究

从极端事件再现时间的角度研究了中国极端高、低温事件再现时间序列的长程相关性、群发性以及二者的关系。发现极端温度事件再现时间序列具有长程相关性,表征长程相关性的标度指数分布存在着明显的区域性特征,并与大气环流有关,当中国大陆在盛夏或隆冬稳定的西风环流控制下,极端温度的长程相关性较好,标度指数较大。通过定义极端事件的群发指数,对极端高、低温进行研究,发现具有长程相关性再现时间序列的极端温度呈现群发现象,且极端温度再现时间序列的标度指数和群发指数二者在空间分布上有较好的对应,极端温度再现时间序列的长程相关性可能是导致极端温度群发性的原因。从年际变化的角度看,极端高温Ⅰ级群发区域的群发指数增长趋于平缓,而极端低温Ⅰ级群发区域的群发指数有下降趋势,这与近几十年来全球变暖一致。在年代际尺度上,群发指数分布的演变特征明显,极端高温Ⅰ级群发区域总体面积变化不大,而极端低温Ⅰ级群发区域面积明显减少。因此,极端低温事件群发性减弱很可能是年代际气候变暖的主要原因。     

21世纪前期长江中下游流域极端降水预估及不确定性分析

在全球变暖背景下,极端降水的频率、强度以及持续时间均在显著增加,尤其是对于气候变化敏感的长江中下游流域。由于模式本身、温室气体排放情景以及自然变率存在较大的不确定性,因此未来预估变化的不确定性一直备受关注。为了能够得到对于未来极端降水更为准确的预估结果,使用NEX-GDDP（NASA Earth Exchange Global Daily Downscaled Projections）提供的19个CMIP5降尺度高分辨率数据（0.25°×0.25°）,给出21世纪前期（2016—2035年）长江中下游流域极端降水的可能变化。根据长江中下游流域178个气象站1981—2005年的逐日降水量数据,计算了能够代表极端降水不同特征的指数,在评估模拟能力的基础上给出了21世纪前期RCP4.5情景下极端降水的变化。结果表明,降尺度结果对长江中下游流域极端降水有很好的模拟能力,除R90N外,所有模式模拟其余指数的空间结构与观测的相关系数均超过了0.6。其中所有模式模拟PRCPTOT和R10的相关系数均超过0.95。21世纪前期,长江中下游地区降水趋于极端化,尤其是在流域的西部地区。极端降水日数的变化在减少,表明对于极端降水的贡献主要来自于极端降水日的较大日降水量,而非极端降水日数。未来预估不确定性的大值区主要位于流域的南部地区,流域的西部地区不确定性较低,西部地区极端降水的增加应该受到更多的重视。      

Nighttime fading ofVLF andLF atmospherics in relation to geomagnetic activity

Summary Long-period fading observed in recordings ofVLF andLF atmospherics in meteorologically clear nights exhibits a good correlation with the geomagnetic activity indexA _p . The fading phenomenon occurs more frequently in the case of integrated field intensity of atmospherics than in the case of andLF radio signal transmitted from a certain station. The phenomenon has been analyzed for the monsoon and postmonsoon periods separately, and the results have been discussed in relation to the large-scale travelling ionospheric distubances (LS TID). The modal value of fade periods forVLF andLF atmospherics has been found to be about one hour. It is noted that the correlation of the fade amplitude of highttimeVLF andLF atmospherics versus the geomagnetic activity is frequency dependent and increases fromVLF toLF.     

中国及周边地区气温年代际变化的研究

利用NCEP/NCAR资料对中国及周边地区的气温场作了分析,发现该区域各季节、各高度上的气温10年滑动距平场均有明显的年代际变化,500 hPa冬、夏季咸海地区和日本海地区该气温距平场则有明显的反相关和"跷跷板"现象,且这两地区500 hPa年平均气温变化均含有10年的振荡周期.     

Modeling of fast ice evolution in the Arctic seas

A one-dimensional model of fast ice wind-induced break-up developed before was adapted for two-dimensional case that enabled to explain many regularities of this phenomenon. A numerical scheme is proposed of the integration of the acting stresses and potential resistivity by the fast ice area as well as the method for taking into account the correlation between the wind direction and prevailing coastline orientation that enables to simulate practically any combination of tensile and shearing stresses in the basins of arbitrary shape. The seasonal variability of strengthening ice properties is taken into account. All numerical tests carried out within the frameworks of this investigation demonstrated the qualitative and, partly, quantitative similarity of computation results and regularities observed in nature. The model sensitivity to the variation of some parameters is studied. The limits of model applicability are discussed and the directions of further research are proposed.     

Intermittency and the Exchange of Scalars in the Nocturnal Surface Layer

The determination of nocturnal surface fluxes in low wind conditions is a major problem for micrometeorological studies. The eddy correlation technique, extensively used in field measurements, becomes inappropriate if not enough turbulent activity exists. At the same time, the phenomenon of turbulence intermittency is responsible for the existence of localized events of short duration within which a large fraction of the total nighttime scalar exchange occurs. The scalar flux within a certain intermittent event varies considerably depending on the window used for the flux calculation. In many cases, events with very different time durations occur in the same night, and therefore, the proper determination of the surface flux would require averaging within data windows of different sizes for each event. In this work, the surface exchanges of temperature, moisture and carbon dioxide are analysed at a micrometeorological tower at southern Brazil. Intermittent turbulence is a common occurrence at the location. The analysis shows that the fluxes vary with turbulence intensity and the estimation technique. A variable-window size method for flux estimation is suggested and shown to cause an increase in the magnitude of the nocturnal surface fluxes     

榆林飞播林区土壤地球化学特征

以榆林飞播林区的土壤微生物、土壤养分和土壤可溶性盐为研究对象,对林区土壤可溶性盐的变化规律及其与土壤养分、微生物的相关性进行研究,为水土资源可持续利用以及飞播造林功效的提高提供理论依据.研究表明,研究区土壤属硫酸盐型,土壤层分异特征不显著,土壤仍处于初级发育阶段.土壤总盐与养分的相关性不明显,适当增加K⁺利于真菌的存活和生物量的积累,在1 kg土壤中,每增加1 g K⁺,真菌数量就会增加14个左右.在土层表层,适量减少Cl^-能促进土壤细菌的生长,在40 cm土层的盐分上行过程中出现表聚现象,在土壤中层,出现板结现象,在土壤底层,HCO₃^-和Na⁺质量分数的增加,有利于土壤全氮质量分数的增加,且HCO₃^-的影响力最强.     

Global climate change and variability and its influence on Alpine climate — concepts and observations

Summary The paper discusses annual to decadal climate variability and change in the European Alps by utilizing the procedure of synoptic downscaling, i.e. it investigates the influence of global to continental scale synoptic structures and processes on the regional climate of the Alps. The European Alps lie to the southeast and under the right exit zone of the southwest-northeast oriented axis of the polar front jet over the North Atlantic ocean, in a transition zone between the Azores high and Icelandic low, between oceanic and continental and between Mediterranean and North Atlantic climates. Together with complex topographically induced phenomena like lee cyclogenesis, orographic precipitation, strong downslope winds and thermotopographical circulation systems, this transitional position makes climate studies in the Alps even more interesting. Only a minor correlation can be observed between global climate variability and Alpine climate. In contrast, the Alpine climate is strongly related to processes over the North Atlantic ocean and its sea ice system (e.g. it has a high correlation with the North Atlantic Oscillation and the dynamics and position of the Icelandic low), an area with a rather low climate prediction potential.Since the early 1970's (or just after the Great Salinity Anomaly in the North Atlantic Ocean) the intensification of the wintertime westerly jet over the North Atlantic area led to a noticeable northwest-southeast mass transport in the exit area of the jet over Central Europe, leading to pressure and temperature rises and an increase in the amount of precipitation. There is a question over whether this phenomenon is a consequence of natural climate variability or the beginning of an anthropogenic climate change.With 16 Figures     

黄河源区重力波势能值计算及其与降水量关系的分析

本文基于1960—2016年的降水量数据分析了黄河源区降水量的分布特征,并利用COSMIC掩星数据计算得到2008年黄河源区的重力波势能值（Potential Energy,Ep）,分析其变化特征,进而运用小波相干分析法探究黄河源区重力波势能值与降水量的相关性。结果表明：1） 黄河源区多年平均降水量受海拔高度影响显著。2） 对不同月份每一不同高程下的Ep值进行分析,得到2008年黄河源区重力波势能值随海拔高程及季节的变化趋势。3） 在2008年黄河源区呈现出：冬夏两季降水量存在较大差异,而重力波势能值同样存在明显的季节性差异,且与逐月平均降水量具有负相关的趋势。此现象是由于山坡地形的动力抬升作用影响和重力波对湿润气流的拖曳作用影响在不同时段占优。4） 黄河源区重力波和降水有着显著相关性,降水对于重力波有着很好的响应。     

A 150-year reconstructed summer Asian�CPacific Oscillation index and its association with precipitation over eastern China

Reconstructing the long-term series of the East Asian summer monsoon (EASM) indices may help understand long-term variability of EASM and its associations with precipitation. In this study, the summer middle?Cupper tropospheric temperature over the Asian?CNorth Pacific sector is reconstructed from sea level pressure during the past 150?years, and then an atmospheric thermal contrast between Asia and the North Pacific, called the Asian?CPacific Oscillation (APO) index, is calculated from the reconstructed temperature. The results show that the APO phenomenon may occur in the reconstructed temperature fields, and its index has a significant positive/negative correlation with SST over the extratropical North Pacific/the tropical central?Ceastern Pacific in the past 150?years. The reconstructed summer APO index shows inter-decadal variability, with a positive phase in the 1870?C1890s, the 1920s, and the 1940?C1970s, indicating a stronger thermal contrast between Asia and the North Pacific, and with a negative phase in the 1860s, the 1900?C1910s, and the 1980?C1990s, indicating a weaker thermal contrast. Corresponding to a higher APO index in earlier decades of the twentieth century, there are more rainfall to the south of the Yangtze River and over North China and less rainfall over the Huaihe River valley. In the recent decades, however, more- and less-rain belts shifted southwards when the APO index is higher. During 1850?C1900, the reconstructed APO index also showed a significant positive correlation with precipitation in some regions of North China.