中国东部地区降水季内变化的季节锁相

用１９５４－１９８３年５－８月的逐日降水资料分析了中国东部地区降水的气候特征，并讨论了它同东亚季风季节内变化的联系。结果发现，江淮梅雨同华南夏季风降水都具有季节锁相特征，前者呈单峰分布，后者呈双峰分布。同时，降水量的季内变化均具有２０－２５天的周期振荡特征。江淮流域降水的峰值和华南地区的第一个峰值主要受副热带季风影响，同夏季风的季节性北进和加强有关，华南地区第二个降水峰值受南海热带季风影响，与同期     

Sq内外源电流体系中国地区变化特征

利用球冠谐分析法对2009年我国35个绝对观测地磁台站的Sq太阳静日变化进行内外源场分离,反演得到三个劳埃德季节(冬季D,分点E,夏季J)相应的内、外源等效电流体系,结果表明Sq外源电流体系在该区域D、E、J三个季节的电流涡中心强度分别为56.2 kA、137.7 kA、137.9 kA,电流涡中心位置的地方时由冬季的1124LT前移至夏季的约1030LT;Sq内源电流体系在该区域D、E、J三个季节的电流涡中心强度分别为21.1 kA、63.4 kA、72.7 kA,电流涡中心位置的地方时由冬季的1100LT前移至夏季的约1000LT.     

Seasonal and gender-related differences in morphometric features and cellular and biochemical parameters of Carcinus aestuarii from the Lagoon of Venice

In this study, the seasonal variations in the morphometric features and in the cellular and biochemical parameters of the haemolymph were investigated in both male and female crabs (Carcinus aestuarii). Crabs were seasonally (November 2010–August 2011) collected from the Lagoon of Venice, and the moult stage, weight, width and length of the carapace, and width and length of the bigger chela were evaluated. In addition, the total haemocyte count (THC), haemocyte diameter and volume, haemolymph glucose and total protein levels, and haemolymph phenoloxidase (PO) and N-acetyl-β-glucosaminidase (NAG) activities were measured. The results demonstrated that the collected crabs were all in the intermoult stage and that the males were bigger than the females. A two-way ANOVA revealed a significant effect of season on the THC and the haemocyte volume and a significant influence of gender on the haemocyte diameter. Season and gender significantly affected the haemolymph glucose concentration, whereas haemolymph protein levels were dependent only on the season. In addition, both season and gender significantly influenced the PO and NAG activities in the haemolymph. Overall, the results demonstrated that crab morphometric features as well as haemolymph cellular and biochemical parameters varied markedly as a function of both season and gender.     

Temperature trend analysis in the glacier region of Naradu Valley,Himachal Himalaya,India

Two and a half decade (1985–2009) surface air temperature from Giovanni database available for the Naradu valley at High Himalaya Mountain range of Himachal Pradesh has been analysed to determine the changes in the maximum, minimum and mean air temperatures. The analysis was subjected for seasonal, annual and monthly basis and revealed a tendency towards warmer years all around, with significantly warmer winter and more significant increase in minimum temperatures. The annual maximum, minimum and mean temperatures have increase by 1,41 °C, 1,63 °C and 1,49 °C, respectively. The seasonal analysis indicates that the tendency is more pronounced in winter followed by post-monsoon, pre-monsoon and monsoon season. The trends were also examined on a maximum temperatures, and it showed a significant warning in all the months in annual mean, minimum and maximum temperatures, except February during the period of 1985–2009 in the valley. Different trend detection statistical tools have been exercised by using variety of non-parametric tests and all are in agreement.     

Estimation of seasonal changes in the flow of Shirase Glacier using JERS-1/SAR image correlation

This paper presents estimates of detailed seasonal variations in ice-flow velocity for Shirase Glacier calculated using data obtained by Japanese Earth Resources Satellite-1 (JERS-1) synthetic aperture radar (SAR). We used 12 pairs of images (44-day repeat cycle) over the interval from 30 April 1996 to 1 July 1998 to estimate ice-flow fields using an image correlation method. Geometric registration was performed with reference to the RADARSAT Antarctic Mapping Project (RAMP) image dataset. Error analysis based on feature mismatch indicated an absolute error of ±0.30 km/a and relative error of ±0.04 km/a in the estimated flow velocity. The obtained ice-flow velocity increases rapidly from the upstream region (1.18 km/a) to the grounding line, where it becomes stagnant (2.32 km/a), before accelerating gradually to 2.62–2.82 km/a in the downstream region and then increasing to 3.05–3.50 km/a at the terminus of the floating ice tongue. The ice-flow velocities in the downstream region are highly variable, depending on both the distance from the grounding line and the observed epoch (season). Most of the obtained seasonal variations in ice-flow velocity at the floating ice tongue are within the range of the associated error estimate, but the annual difference between 1997 (3.11 km/a) and 1998 (3.50 km/a) is significant, reflecting a possible acceleration in the ice-flow velocity in association with the disappearance of the floating ice tongue between April and May of 1998. In terms of the summer–winter difference in averaged air temperature, the large difference recorded in 1997 (17.0 °C) relative to 1996 (13.9 °C) corresponds to a reduced ice-flow velocity in 1997 (approximately 0.20 km/a) relative to that in 1996 (approximately 0.30 km/a), indicating interactions between air, sea ice, and glacier flow in Lützow-Holm Bay.     

东亚地区陆地植被净初级生产力与夏季气候的模拟

利用中国科学院大气物理研究所(IAP)一个海洋-大气-动态植被耦合模式(GOALS-AVIM),进行了100年模拟积分.基于模拟结果,对东亚地区的植被净初级生产力(NPP)、降水、地面气温和短波辐射的季节变化进行了标准化对比,分析了NPP的时空格局与气候因子(气温、短波辐射和降水)的关系;利用奇异值分解(SVD)对东亚夏季降水场和NPP的关系进行分解.结果表明,夏季东亚地区植被NPP及相关气候因子的时空变化规律明显,耦合模式可以很好地模拟出观测存在的降水及NPP、LAI(叶面积指数)大值区随季节北移南退的形态;由于耦合模式中AVIM的双向特点,模式模拟的NPP与其他物理场的季节变化有很强的对应关系,而且在不同时间和地区,NPP与降水、地面气温、短波辐射表现出不同的对应关系,其中植被NPP时间变化与气温和降水的相关性都较高;从NPP场和降水场夏季逐月标准化距平奇异值分解的空间分布模态来看.NPP与降水在时空场上表现出很强的耦合性,NPP的空间格局与降水存在较好的相关性,不同地理位置的相关性强弱不同,分解出的降水场异常相关模态也再现了东亚夏季降水移动的时空特征,同时东亚雨带随季节变化与NPP的气候变率表现出不同的对应模态.     

Changes in the seasonal amplitude of northern ecosystem productivity under future global warming

Observations have shown a largely enhanced seasonal amplitude of northern atmospheric CO₂ in the past several decades, and this enhancement is attributable to the increased seasonal amplitude of northern net ecosystem productivity (NEP amplitude). In the future, however, the changes in NEP amplitude are not clear, because of the uncertainties in climate change and vegetation dynamics. This study investigated the changes in NEP amplitude north of 45°N under future global warming by using a dynamic global vegetation model (DGVM). The authors conducted two sets of simulations: a present-day simulation (1981–2000) and future simulations (2081–2100) forced by RCP8.5 outputs from CMIP5. The results showed an overall enhanced northern NEP amplitude under the RCP8.5 scenario because of the increased maximum NEP and the decreased minimum NEP. The increases (decreases) in the maximum (minimum) NEP resulted from stronger (weaker) positive changes in gross primary production (GPP) than ecosystem respiration (ER). Changes in GPP and ER are both dominantly driven by surface air temperature and vegetation dynamics. This work highlights the key role of vegetation dynamics in regulating the northern terrestrial carbon cycle and the importance of including a DGVM in Earth system models.摘要观测显示过去几十年北半球大气二氧化碳季节幅度大幅增加, 这主要是由北半球陆地净生态系统生产力季节幅度的增加所致. 但是, 因为气候变化和植被动态的不确定性, 未来陆地净生态系统生产力季节幅度的变化还很不清楚. 本工作利用全球植被动力学模式研究了全球变暖背景下北纬45°以北陆地净生态系统生产力季节幅度的变化. 作者做了两大类试验: 当代试验 (1981−2000) 和CMIP5 RCP8.5 变暖情景驱动的未来试验 (2081−2100) . 结果显示, 在RCP8.5变暖情景下北半球中高纬陆地净生态系统生产力季节幅度整体增加, 这是因为陆地净生态系统生产力的月最大值增加且月最小值减小. 最大 (最小) 陆地净生态系统生产力的增加 (减小) 是由于总初级生产力的增加强 (弱) 于生态系统总呼吸. 总初级生产力和生态系统总呼吸的变化都主要受地表气温和植被动态的驱动. 本工作强调了植被动态对北半球中高纬陆地生态系统碳循环的关键调制作用, 也强调了在地球系统模式中包含全球植被动力学模式的重要性.     

IAP AGCM 4.1对淮河流域夏季降水的预报技巧评估

基于中国科学院大气物理研究所新一代大气环流模式IAP AGCM 4.1共30 a(1981—2010年)的集合回报试验结果,评估了模式对淮河流域夏季降水的预报技巧。分析结果表明,模式总体上可以较好地再现出淮河流域夏季平均降水南多北少的空间分布特征,其中模式模拟的6月降水量与观测值的空间相关可达0.93。但降水强度与观测相比具有系统性的偏差,且模式模拟的降水年际变率显著偏弱。基于降水距平相关系数的确定性预报技巧分析表明,模式对流域西南部夏季降水的预测技巧较高,达到0.2以上,且模式对6月降水异常的预测能力相对最好,7月次之。针对淮河不同子流域的预报技巧分析表明,IAP AGCM 4. 1对蚌埠、鲁台子、王家坝水文控制站以上集水面积的夏季面雨量异常具有一定的预报技巧,30 a集合回报的时间相关系数分别为0. 11、0. 13、0. 16。基于降水等级的概率预报技巧评估表明,模式对7月淮河流域南部少雨事件具有很好的预报能力,同时对6月流域中部多雨事件的预报技巧也较高。     

Characterization of C2−C4 NMHCs distributions at a high altitude tropical site in India

Air samples were collected covering a full diurnal cycle during each month of the year 2002 at a mountaintop of Mt. Abu (24.6^∘ N, 72.7^∘ E, 1680 amsl). These samples were analyzed for C₂−C₄ NMHCs using a gas chromatograph (GC) equipped with flame ionization detector (FID). The seasonally averaged diurnal distributions of these NMHCs do not show significant variations in the summer season. While sharp peaks in the diurnal variation of some species during evening hours are additional features apart from higher levels in all NMHCs in the winter season. The seasonal variations in relatively long lived species (e.g. ethane, propane and acetylene) are observed to be more pronounced compared to those in reactive species (e.g. ethene, propene and butanes). The seasonal changes in transport patterns seem to be more dominant factor at this site for the observed variations in NMHCs than changes in OH radical concentration. The annual mean mixing ratios of ethane, ethene, propane, propene, i-butane, acetylene, and n-butane are 1.22 ± 0.58, 0.34 ± 0.24, 0.46 ± 0.20, 0.17 ± 0.14, 0.21 ± 0.18, 0.41 ± 0.43, and 0.31 ± 0.35 ppbv, respectively. Only few pairs of NMHCs are observed to show good correlations, mainly due to transport of air masses with different degree of photochemical processing. A comparison of this measurement with data reported for other remote sites of the globe indicates lower levels of light NMHCs in the tropical sites. The annual mean mixing ratios of various C₂−C₄ NMHCs at Mt. Abu are lower by factors ranging between 3 to 9 compared to a nearest urban site of Ahmedabad. The annual mean propylene (propene) equivalent concentrations of about 1.12 and 8.62 ppbC were calculated for Mt. Abu and Ahmedabad, respectively.     

Seasonal export and sediment preservation of diatomaceous, foraminiferal and organic matter mass fluxes in a trophic gradient across the SE Atlantic

Seasonal deposition fluxes of sinking phytoplankton, zooplankton and major mass compounds (i.e. calcium carbonate, biogenic opal and organic matter), intercepted by deep-moored sediment traps, are contrasted with their sediment accumulation rates over the 2700 m deep central Walvis Ridge in the oligotrophic SE Atlantic. These data provide the first seasonally resolved record of biogenic particle fluxes in the South Atlantic Central Gyre and serve as the oligotrophic end member of a gradient across the Benguela system to the highly productive coastal upwelling off Namibia. Maximum fluxes at the central Walvis Ridge were deposited in early austral spring, following winter deepening of the surface mixed layer and associated nutrient entrainment. Nearly 25% of the annual mass flux arrived in October, when sea surface temperature rose, deep vertical mixing halted and surface production collapsed. The annual flux of diatoms was dominated by small specimens of Nitzschia bicapitata (60%) whereas Globorotalia inflata dominated the foraminiferal fluxes (25%). Diatom diversity dropped significantly during the bloom periods, when up to 80% was composed of small N. bicapitata, but foraminiferal diversity remained about constant. The diatom flux maximum, together with those of biogenic silica and organic matter, preceded those of the foraminifera, pteropods, carbonate and total mass by 1 week. Fluxes of the left- and right-coiled shells of the deep-dwelling foraminifer Globorotalia truncatulinoides peaked in different seasons, a distinctive ecological behaviour which merits their taxonomic recognition as separate species. These findings testify to recent evidence for the existence of several genetic species within G. truncatulinoides and now suggest that such species may also have different seasonal responses.The Benguela trophic gradient showed a shoreward increase in particle fluxes, but differences were surprisingly small, testifying to only moderately enhanced export productivity and deposition at the Namibian margin relative to the oligotrophic central gyre. From the open ocean toward coastal upwelling, small and weakly silicified diatoms were substituted by other, larger and more heavily silicified species, possibly in response to decreased silica limitation. Foraminiferal deposition fluxes were increasingly dominated by G. inflata, accompanied by a change-over from many warm- to few cold-water minor species. The late winter maximum at the Namibian margin and the early spring maximum at the central Walvis Ridge were generated by the same process of collapsing surface productivity in response to the shut down of nutrient entrainment at the winter to summer transition, although delayed by up to 2 months in the Central Gyre. At the sediment-water interface, intense degradation of organic matter and biogenic silica resulted in poor preservation accompanied by pronounced changes in the species composition of siliceous phytoplankton. Of all particle groups at the central Walvis Ridge, only the export of foraminiferal shells appeared to be fully transferred into the sediment, and through their species assemblage to provide a sedimentary record of past seasonal productivity conditions of the upper ocean.