中国半个世纪以来夏季降水量变化总趋势

全球气候变化已经影响到人类生存环境的方方面面.全球升温及其幅度的区域差异,必然引起降水在区域分布的变化.文章利用160站点的夏季降水资料,分别计算出各个站点1951-2002年的变化斜率,以展示我国各地在这半个世纪中的降水总趋势变化的区域差异.通过分析发现,降水量总的变化趋势存在着随纬度而变化的规律:31°N以北区域近半个世纪降水量总的变化趋势是减少,31°N以南地区降水量以增加为主.40°N以北地区的降水变化幅度相对要小得多.区域上,中国西北和东南存在一个降水增多的趋势.中国降水的区域变化,在季风区受季风强弱变化影响;在非季风区,受西风强弱变化影响.     

中国降水量高度效应及全球升温对它的影响

利用中国气象中心160站点的实际观察资料,对中国半个世纪的降水变化进行了系统分析,发现中国的夏季降水量与海拔高度存在着很好的反相关关系;同时,全球升温使得降水量的高度效应增强,主要表现为高海拔降水量海拔效应明显增强,这主要是由全球升温引起环流系统增强所引起的.     

中国种子植物物种丰富度的大尺度分布格局及其与地理因子的关系

地理因子对物种多样性空间分布格局的影响具有重要意义.文章利用大尺度的物种分布数据以及地理信息,结合GIS和数理统计方法,探讨了中国种子植物物种丰富度的空间分布格局及其与地理因子的关系.结果表明,从南到北,研究区域内物种丰富度总体上呈递减趋势;在经度梯度上,从东到西,物种丰富度呈递增趋势,这可能与其它地理因子的影响有关;在排除其它因子影响的情况下,物种丰富度随着面积的增加,呈递增趋势.但在其它地理因子的综合影响下,面积的影响作用被掩盖或弱化.物种丰富度随着海拔变幅的增加,呈显著递增趋势;物种丰富度与纬度变幅、经度变幅之间不存在显著的(偏)相关性.总体上,纬度、面积和海拔变幅均显著影响物种丰富度的分布格局,但相对而言,面积和纬度起着更为重要的影响.相对海拔变幅而言,海拔变幅与纬度之比值能更好地反映"生境异质性"效应,说明,海拔梯度的"纬度效应"值得关注.     

鹰潭地区大气降水中氢氧稳定同位素特征研究

降水中氢氧稳定同位素组成与降水地区各种气象因素变化密切相关。同时,降水中氢氧稳定同位素关系是水同位素应用的主要基础,对深入研究降水中水汽来源,地下水补给等水循环过程具有重要意义。根据江西鹰潭地区2012年4月至2013年3月大气降水中氢氧稳定同位素组成和气象资料,研究了该地区大气降水中氢氧稳定同位素关系及降水量,温度等气象因素对氢氧稳定同位素组成的影响。研究表明,该地区大气降水线方程为δD=8.61δ18O＋18.34（n=72,R2=0.98）,与全球大气降水线方程（δD=8δ18O＋10）相比,鹰潭地区大气降水线的斜率和截距均偏大,这与凝结物在未饱和大气中降落时重同位素的蒸发富集作用有关,同时反映了该地区湿润多雨,降水过程中受二次蒸发影响较小的气候特点。该地区降水中δD （-113.3‰～7.5‰）、δ18O（-14.9‰～-0.9‰）和氘盈余（3.8‰~23.2‰）变化幅度很大并呈现出明显的季节性变化,夏半年（4-9月）δD、δ18O与氘盈余均显著低于冬半年（10-3月）（P＜0.01）,反映出不同季节降水的水汽来源及蒸发条件的差异。对该地区降水同位素与降水量和温度相关性的分析表明,降水中δ18O 与降水量和温度存在显著负相关关系,方程式分别为：y=-0.056x-4.7（R2=0.39,P＜0.01）和y=-0.203x-2.99（R2=0.23,P＜0.01）,说明该地区降水中氢氧稳定同位素存在显著的降水量效应和反温度效应。     

郑州与福州降水同位素特征及水汽来源对比分析

研究基于郑州与福州两地区GNIP(1985—1992年)大气降水同位素资料,对其大气降水同位素的季节变化以及环境因子进行比较分析。结果表明,郑州地区较福州地区季节变化明显,且两地区与温度和降水量均呈现负相关关系;根据两地区大气降水线方程得出,福州地区大气降水线方程斜率和截距大于郑州地区;两地区的d-excess值夏季高,冬季低;福州地区受台风影响,两地区降水量差别较大导致降水量在决定两地区月加权平均d-excess值时,福州地区整体比郑州地区偏大;采用MeteoInfo软件,并利用由美国国家大气研究中心所提供的气象资料,对两地区气团轨迹进行后向模拟,比较分析得出:郑州地区在夏季大部分水汽来自南海,春季、秋季和冬季的水汽均来自北方大陆;福州地区在夏季的水汽全部水汽来自低纬度的海洋,而春季、秋季和冬季的水汽仅有少部份来自北方大陆。     

香港地区大气降水的D和18O同位素研究

研究了香港地区近20 a(1986-2002)大气降水的氢、氧同位素组成,提出了大气降水线方程为6D=8.13δ18O+11.392,并与全国及全球降水线方程进行对比,揭示了该方程的特征.对全年氘盈余及降水线特征的研究表明.香港地区全年降水来源较为单一,主要为海洋性气团,夏季大气降水同位素组成主要受夏季风或夏季台风的影响,加权平均月降水6值与月降水、月气温均呈负相关关系;降水中δD与δ18O的降水量效应明显.且该影响远远掩盖了温度效应.     

1951─2012年三峡库区降水时空变化研究

对区域降水时空分布变化趋势的分析可以为区域水资源的合理管理与利用提供参考,利用三峡库区及周边共27个气象站点的逐月降水数据,通过线性倾向统计、滑动平均两种方法对三峡库区1951─2012年年均、雨季、旱季降水与降水日数的变化趋势进行了研究,并利用多元回归分析对三峡库区内年均降水量和降水日数的空间分布情况进行了分析。结果表明,三峡库区近62 a来的年均、年均雨季、年均旱季降水量和年均降水日数都有减少趋势,年均降水日数的减少趋势比降水量的减少趋势更加显著,并且降水日数明显减少的时间要早于降水量,这表明平均每个降水日内的降水量呈增加的趋势,也即短历时强降雨事件呈增加趋势。多年平均降水量与经度(P=0.081)、纬度(P=0.367)的相关性均不显著,而与海拔高度(P=1.90E-4)达到极显著相关水平。多年平均降水日数与经度(P=0.539)相关系不显著,而与纬度(P=8.77E-4)和海拔高度(P=1.82E-12)均达到极显著相关。降水量和降水日数均与海拔高度达到极显著正相关,可以利用海拔高度相对准确预测研究区内年降水和降水日数的空间分布特征,海拔每升高100 m,对应降水量与降水日数分别约增加30 mm、4.5 d。     

内蒙古地区近25年植被对气温和降水变化的影响

利用1982—2006年内蒙古地区GIMMS-NDVI和降水量、气温数据,分析了不同植被类型对气温和降水变化趋势的影响。结果表明：近25年来内蒙古地区气温整体上呈上升趋势,降水量呈微弱降低趋势,西部荒漠区呈暖湿化趋势,中东部草原、森林等植被类型区呈暖干化趋势;从不同植被类型NDVI与平均气温和降水量的变化趋势率相关分析表明,NDVI值越低,升温趋势越明显,其中春季和秋季各植被类型间NDVI与季均气温升高趋势率呈显著和较显著的相关,夏、冬季关系不明显;植被NDVI越高,降水量减少趋势越明显。基于栅格的NDVI与气温升高幅度、降水变化趋势相关分析表明,年均气温升高幅度基本随NDVI的增加而降低,其中春、夏和秋季的季均气温升高幅度均随NDVI的增加而显著降低,冬季趋势不明显;而年降水量减小趋势率随植被NDVI的增加而显著增加,其中春季和冬季NDVI变化对降水的变化几乎没有影响;夏季和秋季均表现为随NDVI的增加,降水减小趋势率呈增加趋势。     

全球升温下中国温度区域变化的稳定性

利用中国气象中心160站点的气温观测资料,对中国20世纪后半期的气温变化进行方差分析,结果发现气温变化幅度有显著的纬度效应:纬度越高,方差值越大,说明气温变化的幅度也越大。在季节上,气温变化幅度差异显著,普遍是冬季大,夏季小。气温变化幅度的纬度效应在区域分布上,冬季的纬度效应出现在35°N以北,35°N以南不存在纬度效应;夏季的纬度效应表现在34°N以南,34°N以北没有明显的纬度效应。30°N～35°N之间的地带是冬夏季节差异最小的地带,从这一地带开始,不管往南还是往北,气温变化的季节差异都趋于增大。这种格局与我国升温的区域分布是一致的,说明我国最近半个世纪以来的气温变化是持续升高的。最后对气温变化的区域差别进行了机制上的探讨。     

天宝岩自然保护区森林景观格局与环境关系的尺度效应分析

为揭示景观格局内演机制,在3S技术平台支撑下,借助TM遥感像图、植被分类图和二类调查数据,并引入CCA(Canonical Correspondence Analysis)排序方法,对天宝岩森林景观格局与环境的关系及其尺度效应进行定量分析.结果表明:随着取样尺度的递减,排序轴各特征值之和呈增大趋势,依次为:3.137、3.349、3.484、4.660及4.848;而累积景观–环境解释量和景观–环境相关系数皆呈先增后减的趋势,分别在scale3和scale2达到最大;景观类型分布呈现较为明显的纬度梯度变化规律(纬度与第一轴的相关系数:-0.2019~-0.3789)和垂直分布规律(海拔与第一轴的相关系数:-0.3218~-0.4760),其中沿纬度梯度上分布的景观类型依次为:竹林、落叶阔叶林、针阔混交林、农田、常绿阔叶林、山顶矮曲林、常绿针叶林、泥潭藓沼泽、灌草丛;在较低海拔上分布的景观类型主要有竹林和农田,在较高海拔上分布着泥潭藓沼泽、灌草丛和山顶矮曲林;景观格局与环境关系具有尺度效应,环境因子对景观格局分布的影响程度随着尺度的变化而变化.图2表2参36     

聚合铝的形态稳定性及其动电特性的研究

本文采用改进的Ａｌ－Ｆｅｒｒｏｎ快速测定法研究了混凝过程中铝盐与聚合铝水解形态的转化规律及稳定性，并对混凝反应过程中铝与聚合铝溶解－沉淀形态分布与理论溶解度进行了对比，同时采用流动电流技术直接测定了铝盐与聚合铝絮凝剂的荷电状况，最后对发生在混凝过程中铝与聚合铝最佳凝聚形态进行了讨论。     

庐山春季降水与云雾水化学组成的比较

庐山春季高山降水和云雾水均已严重酸化，所采样品的ｐＨ值全部小于５．６，主要酸性物质是硫酸，硝酸占次要地位；云雾水中离子浓度高于降水，且酸度强于降水；对不同相态降水的比较表明，固相降水组成比雨不高２－６倍，但ｐＨ值比雨水高０．６。而氧化性物质Ｈ２Ｏ２在降水中浓度高于云雾水中浓度，液相降水中浓度于固相降水。     

羟基磷灰石对沉积物中重金属释放特性的影响

以羟基磷灰石掺杂前后模拟重金属污染沉积物为研究对象,利用混匀释放实验及化学连续萃取法分析沉积物中重金属的释放特征及形态分布特性,考察了羟基磷灰石对重会属污染沉积物中Cu、zn、Pb、Cd稳定性的影响.结果表明不同来源模拟污染沉积物中松花江沉积物中的重金属最易重新释放,而伊通河沉积物中的重金属释放量最小;同时伊通河沉积物中残渣态重金属的比例较其它沉积物高很多,而可交换态和碳酸盐结合态的重金属比例较其它沉积物低很多,说明同时进入沉积物中的重金属,伊通河沉积物中的重金属相对稳定一些.羟基磷灰石的掺杂不同程度降低了沉积物中重金属的释放能力,促使沉积物中的重金属由较不稳定结合态向较稳定结合态转化,减小了沉积物中重金属的生物可利用性,增强了重金属的稳定性.     

Effects of precipitation and temperature on rain-use efficiency of China's forests北大核心CSCD

Water plays an important role in the growth of plants. It is important to investigate the responses of different ecosystems to precipitation patterns, especially in terms of global changes involving extreme precipitation or drought. However, little is known about the rain-use efficiency (RUE) in China's forests and the correlation of the RUE with the precipitation and other environmental factors. Furthermore, it is unclear whether differences in the forest types or functional groups result in divergent RUE patterns. To investigate the RUE in China's forests, we analyzed the data from 1 266 sampling plots from 17 forest types. The results indicated that: (1) the mean RUE of China's forests is 1.21 g m-2 mm-1. The RUE and precipitation are negatively correlated in all the 17 forest types; (2) the average RUE of broadleaved forests (mainly angiosperms) is higher than that of coniferous forests (mainly gymnosperms), and the angiosperms are more adaptable to changes in the precipitation than gymnosperms; (3) the average RUE of deciduous forests is higher than that of the evergreen forests. The RUE of deciduous forests declines with increasing precipitation to a threshold value. However, the RUE of evergreen forests are unaffected by changes in the precipitation; and (4) the latitude and mean annual temperature are the major factors constraining the RUE under comprehensive environmental factors. We conclude that the mean RUE declines with increasing precipitation to a threshold value, and that the temperature is a crucial factor for RUE. © 2018 Science Press. All rights reserved.     

Stability of eelgrass (<Emphasis Type="Italic">Zostera marina</Emphasis> L.) depth limits: influence of habitat type

Seagrass meadows are generally considered stable although few studies have specified and tested this statement. On the basis of a large monitoring dataset from Danish coastal waters, we aimed to test whether the stability of deep eelgrass populations changes along a eutrophication gradient extending from inner bays over outer bays to open coastal waters. We defined stability in terms of the stability properties of constancy, resilience, and/or persistence. Our data allowed us to investigate the stability property constancy expressed as temporal variability in eelgrass depth limits over a time scale of 10 years. We hypothesised that colonisation depths were large and relatively constant along open coasts because of low and relatively constant levels of nutrients and turbidity. Conversely, colonisation depths were hypothesised to be low and variable in protected bays due to higher and more variable levels of nutrients and turbidity. We found that depth limits increased from inner bays towards open coastal waters, matching declines in nutrient concentration and increases in water clarity and oxygen concentration. Stability expressed as constancy of depth limits did not differ significantly between habitat types, and neither did stability of physicochemical variables. However, when data from all habitat types were analysed together, they showed that eelgrass populations at the depth limit were significantly more constant and thus, in this respect, more stable when occurring in deep waters as compared to shallow waters. Areas of good water quality may thus obtain the double benefit of deeper-growing and more stable eelgrass populations. The most likely reason why this pattern did not appear at habitat-type level is that the habitat types studied represented wide spatial variation in water quality and depth limit. We conclude that the question of whether eelgrass populations are stable depends on the stability property and the ecological situation in question. Populations may be considered unstable in terms of inter-annual variation but stable in terms of long-term persistence. Therefore, the common statement that eelgrass populations are stable is not universally true.Communicated by M. Kühl, Helsingør     

天津植被指数对气候因子响应的敏感性分析

探索植被覆盖与气候变化相互关系是全球环境变化研究领域的重要内容之一,研究特定区域植被对气候变化响应特征对植被重建和生态恢复具有重要意义。然而,目前植被对气候因子响应的敏感性研究还十分缺乏。利用1982—2003年8km×8km的NASA/GIMMS半月合成的归一化植被指数（NDVI）和同期气候数据,研究了天津地区NDVI对气候因子响应特征及其敏感性。结果表明：植被NDVI与气温及降水均有显著非线性正相关关系（P〈0.0001）;在半月平均气温低于0℃时,植被NDVI与气温没有显著性相关,而从气温高于0℃,一直到高于22℃,NDVI与气温的关系均达到显著性水平（P〈0.05）,但相关性是逐渐降低的;当半月平均气温高于23℃及以上时,NDVI与气温没有显著的相关关系（P〉0.05）;当半月降水量〉0mm时,NDVI与降水存在极显著正相关关系（P〈0.0001）,随着降水量的增加,相关关系减弱,在降水量大于50mm时,NDVI与降水没有显著相关关系（P〉0.05）;研究结果证实,天津地区植被指数对气候的响应存有明显的非线性特征,在低温和低降水量条件下植被的响应更为敏感,23℃和50mm分别是该地区影响植被生长的气温和降水阈值。结合1982—2003年逐半月气候条件分析发现,气温的影响主要是春、秋两季,而降水的影响主要表现在春、秋及夏初。     

Role of Rh promoter on increasing stability of Au/Al2O3 catalyst for CO oxidation at low temperature

The Au/Al₂O₃ and Au–Rh/Al₂O₃ catalysts were prepared by deposition–precipitation. The promotional effect of Rh on the performance of the Au/Al₂O₃ catalyst for CO oxidation was studied. The results indicate that using Au/Al₂O₃ catalyst, CO can be completely oxidized at 0°C or much lower temperature but the catalyst deactivated very fast. Rh can improve the stability of Au/Al₂O₃ catalyst more than 10 times, which gives an important hint to develop high stable catalyst for CO oxidation at low temperature.     

Precipitation-driven carbon balance controls survivorship of desert biocrust mosses

Precipitation patterns including the magnitude, timing, and seasonality of rainfall are predicted to undergo substantial alterations in arid regions in the future, and desert organisms may be more responsive to such changes than to shifts in only mean annual rainfall. Soil biocrust communities (consisting of cyanobacteria, lichen, and mosses) are ubiquitous to desert ecosystems, play an array of ecological roles, and display a strong sensitivity to environmental changes. Crust mosses are particularly responsive to changes in precipitation and exhibit rapid declines in biomass and mortality following the addition of small rainfall events. Further, loss of the moss component in biocrusts leads to declines in crust structure and function. In this study, we sought to understand the physiological responses of the widespread and often dominant biocrust moss Syntrichia caninervis to alterations in rainfall. Moss samples were collected during all four seasons and exposed to two rainfall event sizes and three desiccation period (DP) lengths. A carbon balance approach based on single precipitation events was used to define the carbon gain or loss during a particular hydration period. Rainfall event size was the strongest predictor of carbon balance, and the largest carbon gains were associated with the largest precipitation events. In contrast, small precipitation events resulted in carbon deficits for S. caninervis. Increasing the length of the DP prior to an event resulted in reductions in carbon balance, probably because of the increased energetic cost of hydration following more intense bouts of desiccation. The season of collection (i.e., physiological status of the moss) modulated these responses, and the effects of DP and rainfall on carbon balance were different in magnitude (and often in sign) for different seasons. In particular, S. caninervis displayed higher carbon balances in the winter than in the summer, even for events of identical size. Overall, our results suggest that annual carbon balance and survivorship in biocrust mosses are largely driven by precipitation, and because of the role mosses play in biocrusts, changes in intra-annual precipitation patterns can have implications for hydrology, soil stability, and nutrient cycling in dryland systems.     

Modeling radiative effects of haze on summer-time convective precipitation over North China: a case study

We modeled the impact of haze radiative effects on precipitation in North China. Shortwave heating induced by haze radiative effects would reduce heavy rainfalls. Convection was the key factor that whether precipitation was enhanced or suppressed. Precipitation was often suppressed where CAPE, RH and updraft velocities were high. The impact of haze radiative effect on summertime 24-h convective precipitation over North China was investigated using WRF model (version 3.3) through model sensitivity studies between scenarios with and without aerosol radiative effects. The haze radiative effect was represented by incorporating an idealized aerosol optical profile, with AOD values around 1, derived from the aircraft measurement into the WRF shortwave scheme. We found that the shortwave heating induced by aerosol radiative effects would significantly reduce heavy rainfalls, although its effect on the post-frontal localized thunderstorm precipitation was more diverse. To capture the key factors that determine whether precipitation is enhanced or suppressed, model grids with 24-h precipitation difference between the two scenarios exceeding certain threshold (>30 mm or<-30 mm) were separated into two sets. Analyses of key meteorological variables between the enhanced and suppressed regimes suggested that atmospheric convection was the most important factor that determined whether precipitation was enhanced or suppressed during summertime over North China. The convection was stronger over places with precipitation enhancement over 30 mm. Haze weakened the convection over places with precipitation suppression exceeding 30 mm and caused less water vapor to rise to a higher level and thus further suppressed precipitation. The suppression of precipitation was often accompanied with relatively high convective available potential energy (CAPE), relative humidity (RH) and updraft velocities.